0049 AES Ecology, 551 AB, Thursday 8 July 2010
Carlos Polo1, Felipe Galván2, Seth Newsome3, Angélica Barrera4
1Universidad Nacional Autónoma de México, Distrito Federal, Mexico, 2Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja Caifornia Sur, Mexico, 3University of Wyoming, Laramie, Wyoming, United States, 4Centro de Investigaciones Biológicas del Noroeste, La Paz, Baja California Sur, Mexico
Examining Ontogenetic Trophic Shifts in Alopias superciliosus Via δ13C and δ15N Analysis of Muscle and Vertebrae
The bigeye thresher shark Alopias superciliosus has a worldwide distribution in coastal and oceanic waters of tropical and subtropical seas, however, little is known about the ecology of this shark. Here we examine ontogenetic shifts in the diet of A. superciliosus via carbon (δ13C) and nitrogen (δ15N) stable isotope analysis of muscle and vertebrae. A total of 37 muscle and 37 vertebrae were analyzed. Mean (±SD) δ13C and δ15N values in muscle were -15.2 (±0.2‰) and 14.5‰ (±0.2‰) respectively; mean δ13C and δ15N values in vertebrae were -16.7‰ (±0.6‰) and +10.1‰ (±0.3‰) respectively. We found no significant sex-related differences in mean C or N isotope values, but adult males had significantly higher muscle δ13C and δ15N values than juveniles. This pattern suggests that adult males forage more often in coastal habitats and on higher trophic level prey than juveniles, whereas lower muscle δ13C values in juveniles indicate they migrate from coastal to oceanic waters. We found no significant ontogenetic related differences in δ15N for females, suggesting that they forage in similar habitats and on prey that occupies a similar trophic level throughout their life. Lastly, a comparison of tissue types from the same individual shows that δ15N values in muscle is on average 4.4‰ (±0.1‰) higher than vertebrae; muscle δ13C is also higher than vertebrae by 1.5‰ (±0.2‰). Tissue-specific differences in isotope values likely relate to differences in their amino acid composition and the observation that shark muscle contains a high concentration of 15N -depleted urea.
0369 AES Ecology, 551 AB, Thursday 8 July 2010
Jill Olin1, Nigel Hussey2, Michelle Heupel3, Colin Simpfendorfer3, Gregg Poulakis4, Aaron Fisk1
1GLIER, University of Windsor, Windsor, ON, Canada, 2School of Oceans Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey, United Kingdom, 3School of Earth and Environmental Sciences, James Cook University, Townsville, QLD, Australia, 4Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Port Charlotte, FL, United States
Maternal Investment Confounds Stable Isotope Interpretation in Young Individuals
Ontogenetic shifts in diet are common and are often assessed using stable isotopes of carbon (δ13C) and nitrogen (δ15N). However, when considering neonate individuals, interpretation of stable isotope composition is confounded as viviparous species are born isotopically enriched compared to their mothers. To address this, values of δ13C and δ15N were measured in the liver and muscle of neonate and young-of-the-year bull (Carcharhinus leucas) and Atlantic sharpnose (Rhizoprionodon terraenovae) sharks and related to age using umbilical scar stage, a unique characteristic among fishes. Values of δ13C in tissues of both species, and δ15N in muscle of Atlantic sharpnose, declined with age, exceeding the enrichment documented between embryos and their mothers. Decline in stable isotopes was: more evident in Atlantic sharpnose compared to bull sharks, delayed to late scar stages in bull sharks, and greater in liver compared with muscle; highlighting that species-specific life history and tissue characteristics significantly influence maternal isotopic loss. Consideration of maternal investment is necessary in any study using stable isotopes of young individuals, as there is great potential to overestimate trophic position and incorrectly assign carbon source.
0345 AES Ecology, 551 AB, Thursday 8 July 2010
Philip Matich, Michael Heithaus, Craig Layman
Florida International University, Miami, FL, United States
Contrasting Patterns of Individual Specialization and Trophic Coupling in Two Marine Apex Predators
Top predators are often assumed to be dietary generalists and, by feeding on prey from multiple basal nutrient sources, serve to couple distinct food web modules. Yet, there is increasing evidence that individual dietary specialization may be critical to trophic dynamics of predator populations. Individual specialization is well-documented in teleosts, birds, and mammals, but little is known about dietary specialization in highly mobile top predator taxa in marine habitats. Using stable isotope analysis of body tissues with different turnover rates, the dietary patterns of bull sharks (Carcharhinus leucas) and tiger sharks (Galeocerdo cuvier) were investigated to assess dietary specialization. Tiger sharks were largely dietary generalists, but the bull shark population was characterized by a wide trophic niche with many specialized individuals. These differences in individual dietary specialization suggest that marine apex predators may fill very different functional roles in coupling or compartmentalizing distinct food webs depending on ecosystem context, and resource availability, competition, and the spatial patterns of food webs appear to be important factors driving trends in individual dietary specialization. Our study suggests that individual specialization may be an important feature of trophic dynamics of non- mammalian marine top predators and should be explicitly considered in studies of marine communities.
0514 AES Ecology, 551AB, Thursday 8 July 2010
Nigel Hussey1, Sheldon Dudley2, Geremy Cliff2, Sabine Wintner2, Jaclyn Brush1, Aaron Fisk1
1University of Windsor, Ontario, Canada, 2KwaZulu-Natal Sharks Board / University of KwaZulu-Natal, Durban, South Africa
Documenting the Trophic Structure of the Shark Assemblage off Kwazulu- natal, South Africa Using Stable Isotopes
When considering that most sharks are apex predators, concern has been raised over their large scale removal and this effect on ecosystem structure, stability and function. Stomach content analysis has provided detailed insights into snapshot feeding habits and coarse resolution trophic level calculations, but tissue-integrated measures of trophic position and niche width of individual species within a shark assemblage remain largely unknown. Additionally, size based variation in trophic position of sharks is little understood. Here we report on the trophic structure of the shark assemblage off KwaZulu-Natal, South Africa, through the measurement of the isotopic composition (δ15N and δ13C) of white muscle tissue. We document the δ15N trophic structure for 17 species of sharks encompassing the principal ‘large’ shark families; Carcharhinidae, Sphyrnidae, Lamnidae and Odontaspididae, and include individuals from the families Triakidae, Alopiidae and Rhincodontidae. Furthermore, we present the range in δ13C values of the shark assemblage using 13C enrichment (coastal) and 13C depletion (pelagic) as a measure of coarse resolution movement patterns. The fact that the stable isotopes of nitrogen and carbon are intrinsically linked will be discussed with reference to disentangling trophic position and movement patterns.
0432 AES Ecology, 551 AB, Thursday 8 July 2010
Bailey McMeans1, Michael Art2, Aaron Fisk1
1University of Windsor, Windsor, Ontario, Canada, 2Environment Canada, Burlington, Ontario, Canada
The Feeding Behavior of Greenland Sharks Based on Stable Isotope and Fatty Acid Analysis of Multiple Tissues
The Greenland shark (Somniosus microcephalus) is one of only two sharks that inhabit seasonally ice-covered waters. However, few data exist regarding their feeding behavior and potential role in marine ecosystems. Greenland sharks consume a variety of prey taxa and likely have slow tissue turnover due to their large size and slow growth. Thus, investigating important energy sources and temporal patterns of feeding behavior in Greenland sharks using stomach contents and chemical tracers is potentially problematic. The objective of the present study was to analyze multiple Greenland shark tissues with different turnover times (i.e. muscle, liver, red blood cells, blood plasma) for stable nitrogen (δ15N) and carbon (δ13C) isotopes and fatty acids (FA) to investigate seasonal patterns in feeding behavior. Regarding δ13C and δ15N, no differences were observed in any tissue between open-water and ice-cover, indicating that neither trophic position nor carbon sources of Greenland sharks differed with season. Diet breadth, indicated by coefficients of variation, were also similar between seasons within each tissue, further supporting the lack of seasonal diet differences in Greenland sharks. Fatty acid profiles of Greenland sharks differed between tissues, but not between seasons. However, blood plasma FA profiles were similar to blubber FA profiles of ringed seals (Pusa hispida), indicating recent consumption of marine mammal by Greenland sharks. The use of multiple tissues in the present study was useful for indicating that Greenland sharks do not differentially feed between seasons and that marine mammals are likely an important energy source to Greenland sharks.
0718 AES Ecology, 551 AB, Thursday 8 July 2010
Wade D. Smith1, J. Fernando Márquez-Farías2, Jessica A. Miller3, Selina S. Heppell1
1Oregon State University, Dept. of Fisheries & Wildlife, Corvallis, Oregon, United States, 2Facultad de Ciencias del Mar, Universidad Autonoma de Sinaloa, Mazatlán, Sinaloa, Mexico, 3Oregon State University, Coastal Oregon Marine Experimental Station, Hatfield Marine Science Center, Newport, Oregon, United States
Spatial and Temporal Variation in Vertebral Chemical Composition: Evaluating the Potential to Distinguish Natal Origin from Natural Elemental Markers in Elasmobranchs
Differences in the chemical composition of calcified structures are used to reconstruct environmental history and reveal natal origins, dispersal patterns, spatial dynamics, and metapopulation structure of many marine organisms. Because the use of discrete nursery areas is common among elasmobranchs, distinctive chemical markers may be incorporated into the vertebrae of individuals as they occupy these areas during the first months or years of their lives. We evaluate the assumptions of elemental analysis for the cartilaginous vertebrae of elasmobranchs and compare the variation observed in this study with that reported for the calcified structures of teleosts and mollusks. Vertebrae were collected from young-of-the-year scalloped hammerhead sharks (Sphyrna lewini) from five locations along the Pacific coast of Mexico and Costa Rica in 2007 and 2008 to assess patterns of spatial and temporal variability in elemental composition. Elemental composition was measured using Laser Ablation Inductively Coupled Plasma Mass Spectrometry and the resulting elemental concentrations were expressed relative to their ratio with calcium. Elemental composition (Ba, Cd, Co, Cr, La, Li, Pb, Mg, Mn, Ni, Rb, Sr, Ti, V, Zn, Zr) did not vary between vertebrate within age-0 individuals. However, elemental composition differed significantly between the region of vertebrae that was deposited post-partum in comparison to that which developed while in-utero. Multivariate analysis of variance was applied to examine temporal (intra- and inter- annual) differences in vertebral chemistry within and among sample locations. The ability to successfully classify individual specimens to their site of natal origin was assessed through quadratic discriminant function analysis.
0586 AES Ecology, 551 AB, Thursday 8 July 2010
Heather McCann1, Nigel Hussey1, Aaron Fisk1, Sabine Wintner2, Geremy Cliff2, Sheldon Dudley2, Brian Fryer1
1Great Lakes Institute of Environmental Research, University of Windsor, Windsor, Ontario, Canada, 2KwaZulu-Natal Sharks Board, Umhlanga Rocks, South Africa, 3Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa
Microchemistry of White Shark (Carcharodon carcharias) Vertebrae: A Potential Tool to Examine Life-History Strategies?
The microchemistry of biomineralized structures, such as fish otoliths, is becoming an important tool to elucidate life-history characteristics of marine animals over ontogeny. The corpus calcareum of shark vertebrae grows incrementally preserving a seasonal microchemistry signal (summer /winter) over the lifetime of the animal, similar to fish otoliths. The microchemistry of white shark (Carcharodon carcharias) vertebrae may provide an additional ecological tool to aid in understanding individual life history patterns. I present baseline elemental concentration profiles for several sharks of varying age, size and sex sampled from beach protection nets in KwaZulu-Natal, South Africa. The potential of laser ablation inductively coupled mass spectrometry (LA-ICP- MS) to analyze vertebrae microchemistry is assessed. A suite of elements (ranging in concentration from a few ppb to 1000s of ppm) were quantified using LA-ICP-MS in continuous transects along the corpus calcareum. Barium levels varied across growth bands suggesting ontogenetic movement between nutrient rich upwelling areas and non-nutrient rich areas. A number of non-essential elements (e.g., uranium, lead) also varied across growth bands and may provide insights into ontogenetic migration and depth profiles of individual sharks. A number of essential elements (zinc, copper…) of the embryonic component of the vertebrae were enriched compared to after birth and increased with age to levels approaching those in the embryonic sections. These preliminary results show that a range of elements have suitable detection limits to aid in determining life-history patterns.
0147 AES Ecology, 551 AB, Thursday 8 July 2010
Tobey Curtis1, Camilla McCandless2, John Carlson3, Harold Pratt, Jr.2, Nancy Kohler2, George Burgess4, Gregory Skomal5
1NOAA Fisheries Service, Gloucester, MA, United States, 2NOAA Fisheries Service, Narragansett, RI, United States, 3NOAA Fisheries Service, Panama City, FL, United States, 4Florida Museum of Natural History, Gainesville, FL, United States, 5Massachusetts Division of Marine Fisheries, Oak Bluffs, MA, United States
Seasonal Distribution of White Sharks in the Western North Atlantic Ocean
Despite recent advances in field research on white sharks (Carcharodon carcharias) in several regions around the world, opportunistic capture and sighting records remain the primary source of information on this species in the North Atlantic Ocean. This is due to their sparse distribution and the apparent absence of discrete coastal aggregation sites in this hemisphere. Few studies have attempted quantitative analyses of available data to describe seasonal distribution, population structure, habitat use, and relative abundance. This study builds upon previously published data combined with recent unpublished records and presents a synthesis of over 550 confirmed white shark records compiled over a 210-year period (1800-2009). This is the largest white shark dataset yet compiled for the western North Atlantic. Descriptive statistics and GIS analyses were employed to quantify the seasonal distribution of various sub-components of the population. White sharks range widely along the Atlantic coast of North America (18-51 °N latitude). All size classes were present in continental shelf waters in every month of the year, occurring over a temperature range of 11-28 °C. Median latitude of white shark occurrence varied seasonally, with sharks moving to higher latitudes during the summer months. Core areas of high shark density also varied seasonally, with high density between Massachusetts and New Jersey during summer, and off Florida’s east coast during winter. White sharks are currently prohibited from commercial and recreational harvest in the region, but the level of bycatch in various fisheries remains uncertain.
0263 AES Ecology, 551 AB, Thursday 8 July 2010
Simon Gulak, John Carlson
NOAA Fisheries, Panama City Beach, FL, United States
Habitat Use and Movement Patterns of Pelagic Sharks in the Gulf of Mexico Using Pop-up Archival Satellite Tags
Pop-up satellite tags have been deployed on a number of pelagic shark species in the Gulf of Mexico and US south Atlantic to determine migration, movement patterns and habitat use. Since 2005, one longfin mako, two oceanic whitetip and two bigeye thresher sharks have been tagged in the Gulf of Mexico. However, data have been obtained only for 1 oceanic whitetip shark and 2 bigeye threshers. Data were obtained for a deployment of 20 days for the oceanic whitetip shark and 18 and 113 days for the bigeye threshers. Preliminary analysis suggests oceanic whitetip sharks are extreme epi-pelagic species rarely venturing below the thermocline regardless of time of day or water temperature. However, bigeye thresher sharks demonstrated a diel pattern of vertical movement defined by greater mean depths and larger depth ranges during night time hours. Depth and temperature data also suggested a behavioral change in vertical movements associated with an increase in sea-surface temperatures. All animals were tagged adjacent to the Mississippi delta. After tagging, the oceanic whitetip and one big eye thresher shark moved west following the continental shelf against the Loop Current with the tag popping off near the Yucatan Peninsula. The remaining bigeye thresher also moved west but remained in the same area.
0655 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Nicholas Wegner1, N. Chin Lai2, Kristina Bull1, Jeffrey Graham1
1Scripps Institution of Oceanography, La Jolla, CA, United States, 2University of California, San Diego, La Jolla, CA, United States
Ram Ventilation in the Shortfin Mako, Isurus oxyrinchus: Examining Oxygen Utilization and the Branchial Pressure Gradient Using a Large Water Tunnel
This paper investigates aspects of ram ventilation in a lamnid shark, the shortfin mako, Isurus oxyrinchus, and examines the extent to which intrinsic structural differences in the gill design of elasmobranchs and teleosts may affect the lamnid-tuna convergence for high-performance swimming. The study of makos swimming in a water tunnel demonstrates that, despite differences in gill design, mouth gape, and basal swimming speeds, O2 utilization at the gills and the pressure head driving branchial flow for makos are similar to values reported for tunas. Also comparable to tunas are estimates of both the velocity and the residence time of water in the interlamellar channels of the mako. However, mako and tuna gills differ in the sites of primary branchial resistance. In the mako, much of the total branchial resistance resides with the septal channels, structures inherent to the elasmobranch gill and not present in tunas. The added resistance at this location is compensated by a correspondingly lower resistance at the gill lamellae, which is accomplished through wider interlamellar channels. Although greater interlamellar spacing minimizes branchial resistance, it also limits lamellar number and results in a lower total gill surface area for the mako relative to tunas. The elasmobranch gill design thus appears to constrain gill area and may potentially limit mako aerobic performance in comparison to tunas.
0726 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Cathy Walsh, Stephanie Leggett, Carl Luer, Michael Henry
Mote Marine Laboratory, Sarasota, FL, United States
Effects of Nurse Shark, Ginglymostoma cirratum, Peripheral Blood Leukocytes Following in vitro Exposure to Red Tide Toxin
Blooms of the toxic dinoflagellate, Karenia brevis, occur almost annually off the west coast of Florida. Commonly called “red tides”, these blooms produce neurotoxins, collectively termed brevetoxins (PbTx), that severely impact many species of marine mammals, sea turtles and fish. Effects on immune cells from nurse sharks, Ginglymostoma cirratum, were investigated following in vitro exposure of peripheral blood leukocytes (PBL) from healthy captive nurse sharks to brevetoxin. Differential expression of genes affected by brevetoxin exposure was determined through suppression subtractive hybridization (SSH) experiments. Using unexposed PBL from nurse sharks as control, SSH experiments indicated that genes involved in transporter function, translation initiation, and cell signaling were up-regulated following 18 h exposure to 560 nM PbTx-2, while genes involved in mitosis and inflammation were down-regulated. Real-time PCR conducted on a gene (transmembrane 9 superfamily member 3) coding for a protein with transporter functions exhibited significant gene up- regulation in response to 140 nM PbTx-2. Coincidentally, presence of a functional transport system in nurse shark PBL was indicated by efflux of the fluorescent dye, calcein-AM, by PBL treated with 100 nM PbTx-2 for 25 min. Finally, evidence for metabolism of xenobiotic compounds through conjugated pathways in shark immune cells was demonstrated by LC/MS detection of a glutathione conjugate, GSH-PbTx, following 3 h exposure to 50 μM PbTx-2. This study represents the first report of the effects of brevetoxins on immune cells in an elasmobranch species and suggests that exposure to red tide toxins may have significant implications for immune function in sharks.
0231 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Julieta Jañez, Raúl Zalazar, Dante Di Nucci, Martín Falzone
Temaiken Foundation, Escobar, Buenos Aires, Argentina
Preliminary Reference Blood Parameters for Southern Eagle Ray (Myliobatis goodei) in Captivity
Hematologic studies provide valuable data for animals in captivity and even when there is no information of a species in its natural environment. Information about blood reference parameters for skates and rays is scarce in the literature. The southern eagle ray Myliobatis goodei occurs off Mar del Plata throughout the year and was found as far south as 46°59 ́S. Little is known about the biology of this species in Argentina. We, therefore, initiated a preliminary study to achieve the first reference values about blood hematology and biochemistry for M. goodei in captivity. Blood samples from 19 southern eagle rays (10 females-9 males), maintained in the Temaiken Aquarium were obtained without chemical immobilization. The blood and serum parameters values (mean± S.D.) for males and females were: hematocrit (25.00± 4.39; 24.90± 6.28)%, glucose (22.04±12.66; 14.91±11.90) mg/dl, cholesterol (116.99± 26.28; 124.93± 29.25) mg/dl, triglycerides (157.27± 52.08; 178.17± 67.75) mg/dl, aspartate aminotransferase (25.60± 17.72; 26.12± 19.69) U/l, alanine aminotransferase (25.50± 14.53; 11.35± 12.80) U/l, gamma-glutamyl transpeptidase (16.02± 9.85; 11.58± 9.35) U/l, lactate dehydrogenase (859.90± 478.70; 707.43± 586.68) U/l, pancreatic amylase (219.69± 72.93; 221.95± 79.96) U/l, total protein (5.91± 0.72; 6.45± 0.39) g/dl, albumin (2.29± 0.72; 3.66± 2.38) g/dl, urea (826.84± 140.41; 806.66± 147.47) mg/dl, creatinine (0.99± 0.39; 1.01± 0.58) mg/dl. Significant differences between sexes were detected only for alanine aminotransferase. This reference values will be useful for future evaluation of health status of southern eagle ray both wild and in captivity and mainly to aid in the management of this species in aquaria.
0712 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Sean Hersey, Rebeka Rand Merson
Rhode Island College, Providence, RI, United States
Functional Divergence Among Multiple Aryl Hydrocarbon Receptors in Sharks
The aryl hydrocarbon receptor (AHR) is a member of the basic helix-loop-helix Per- ARNT-Sim (bHLH-PAS) family of heterodimeric transcriptional regulators. AHR is a ligand activated transcription factor that regulates genes in response to persistent environmental pollutants such as dioxins and dioxin-like compounds. In addition, AHR has multiple roles in cell physiology. Squalus acanthias (spiny dogfish) expresses multiple AHR genes. AHR1, AHR2, and AHR3 were cloned and expressed as GFP fusion proteins in mammalian cells. Subcellular localization and response to PCB-126, a typical AHR ligand, was observed by fluorescence microscopy. We performed reporter gene assays to assess the ability of shark AHR1, AHR2, and AHR3 to activate an AHR response element-driven promoter in the presence of a typical ligand. AHR2 rapidly localizes to the nucleus in the presence of a typical AHR ligand and activates the gene reporter. AHR3 is constitutively nuclear regardless of the presence or absence of ligand and supports ligand-dependent reporter activation. AHR1 does not localize to the nucleus or induce expression of the same reporter in the presence of a typical ligand. This functional divergence among AHR1, AHR2, and AHR3 supports the hypothesis that multiple AHR genes present in early vertebrates have distinct functions and indicate partitioning of ligand-dependent and ligand-independent roles of AHR among these gene products. Supported by RI-INBRE grant P20RR-016457 from the National Institutes of Health National Center for Research Resources, and a MDIBL New Investigator Award funded by ME-INBRE (P20RR-016463) and the NIEHS Center for Membrane Toxicity Studies (P30ES-00382820).
0722 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Janis Hall, Rebeka Rand Merson
Rhode Island College, Providence, RI, United States
Genomic Context of Shark Aryl Hydrocarbon Receptors
In order to understand the regulation of genes encoding aryl hydrocarbon receptors (AHR), which are involved in numerous physiological processes and the response to persistent environmental chemical pollutants, we investigated AHR loci in the spiny dogfish shark, Squalus acanthias. Resources for molecular biology and evolution of chondricthyians are scarce, so we screened a bacterial artificial chromosome (BAC) library, EST databases, and performed targeted PCR. BAC plasmids from AHR-positive clones were prepared and then probed for other AHRs. Sequences were also obtained by shotgun sequencing of selected BAC clones. Our results support that tandem duplication of AHR genes occurred prior to the divergence of the Class Chondricthyes from the vertebrate lineage. To further investigate these genes and identify regulatory regions, a “genome walking” approach is underway. Supported by RI-INBRE grant P20RR-016457 from the National Institutes of Health National Center for Research Resources (NCRR), and a MDIBL New Investigator Award funded by ME-INBRE (P20RR-016463) and the NIEHS Center for Membrane Toxicity Studies (P30ES- 00382820).
The Use of Steroid Hormone Concentrations to Determine Individual Variability in theReproductive Cyclicity of the Little Skate, Leucoraja erinacea, from the Western Gulf of Maine MISSING!!!
0354 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Paola A. Mejia Falla1, Enric Cortés2, Fernando A. Zapata3, Andrés F. Navia4
1Fundación colombiana para la investigación y conservación de tiburones y rayas, SQUALUS, Cali, Valle del Cauca, Colombia, 2NOAA-NMFS, Panama City, Florida, United States, 3Grupo de Investigación en Ecología de Arrecifes Coralinos, Departamento de Biología, Universidad del Valle, Cali, Valle del Cauca, Colombia, 4Grupo de Investigación en Ecología Animal, Departamento de Biología, Universidad del Valle, Cali, Valle del Cauca, Colombia
Reproductive Biology of the Round Stingray Urotrygon rogersi in the Pacific Coast of Colombia
We studied reproductive aspects of 1158 individuals of the round stingray Urotrygon rogersi. Specimens were obtained from the artisanal shrimp fishery operating in the Colombian Pacific Coast between March 2006 and March 2009. Females reached greater maximum total length (TL) and weight (37.4 cm and 293 g) than males (32.5 cm and 160 g). Sex ratio of adult males vs. females was 1:1.4 and that of embryos, 1:1. Clasper length increased rapidly between 20.0 and 22.0 cm TL. The smallest mature male measured 20.2 cm TL and the largest immature individual 21.9 cm TL. First maturity was reached at 61.5% of maximum length (TLmax), and TL50 was estimated to be 26.2 cm. Uterus width increased between 22.0 and 23.0 cm TL. The smallest maturing individual measured 18.0 cm TL. The size at first maturity was 54.5% of TLmax and TL50 was estimated at 25.8 cm. Embryos were found in females > 20.4 cm TL and maximum fecundity was three embryos per female (mode=1). A statistically significant relationship between fecundity and maternal size was found. The high percentage of mature individuals in the area and the low number and presence of embryos of all sizes during all months suggest that: 1) parturition in U. rogersi is not seasonal, but rather occurs throughout the year; 2) there is a trade-off between fecundity and length of reproductive cycle; and 3) the study sites are important nursery and reproductive areas for Urotrygon rogersi.
0419 AES Physiology & Reproduction, 552 AB, Thursday 8 July 2010
Lisa Jones1, William Driggers1, Dana Bethea2, Simon Gulak2
1NOAA/NMFS Pascagoula Laboratory, Pascagoula, MS, United States, 2NOAA/NMFS Pamama City Laboratory, Panama City, FL, United States
Reproductive Biology of the Cuban Dogfish (Squalus cubensis) in the Northern Gulf of Mexico.
In the northern Gulf of Mexico, the Cuban dogfish, Squalus cubensis, is the most commonly encountered squalid shark in deepwater trawl and longline catches; however, its reproductive biology remains almost completely unknown. To obtain basic reproductive data for S. cubensis, 72 males and 176 females were collected throughout the northern Gulf of Mexico while conducting fisheries-independent surveys and port sampling. The median STL at 50% maturity for males was 386 mm. All mature males, regardless of date of capture, had semen present in the ductus deferentes and seminal vesicles. The median STL at 50% maturity for females was 464 mm. Ninety-two percent of all adult females captured were gravid, with brood sizes ranging from 1-4 (mean = 2.14, S.D. = 0.77). During mid-late fall, when the majority of samples were collected, embryos were observed in all stages of development, from blastodisc to term fetuses. During the same period, the diameter of the largest ovarian follicle ranged from 5 – 31 mm (mean = 14.96, S.D. = 5.12). The above data indicate that adult males are capable of reproducing throughout the year and the adult female segment of the population exhibits asynchronous reproduction with no resting stage.
Global Genetic Stock Structure of the Copper (Carcharhinus brachyurus) and Dusky Sharks (Carcharhinus obscurus): Interspecific Comparisons and
Implications for Management MISSING!!!
0215 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Megan Winton1, David Ebert1, Lisa Natanson2, Gregor Cailliet1
1Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, United States, 2National Marine Fisheries Service, Northeast Fisheries Science Center, Narragansett, RI, United States
Age, Growth, and Maturity of the Roughtail Skate, Bathyraja trachura (Gilbert, 1892), from the Eastern Bering Sea
Fishery landings of skates in Alaskan waters surpass those of all other U.S. states combined. Many skates possess life history characteristics that may make them vulnerable to exploitation; therefore, the accurate assessment of growth rates, longevity, and reproductive productivity is indispensible in developing management plans. The objectives of this study were to provide age estimates and describe growth characteristics of Bathyraja trachura from the eastern Bering Sea, specifically examining longevity, size and age at maturity, variation in these traits between sexes, and potential differences in growth between two marine ecosystems. Age estimates were determined using counts of vertebral bands in both unstained thin sections and those prepared using a histological method. Observed age estimates from thin sections ranged from 0 to 30 years, with a maximum age estimate of 29 and 30 years for males and females, respectively. Of the four models applied, the two-parameter von Bertalanffy growth function provided the best description of growth and generated estimates of k = 0.078 and L∞ = 985.7 mm TL. No significant differences were detected between the growth of males and females. Median length and age at 50% maturity were estimated at 748.2 mm and 16 years for males and 791.9 mm and 18.6 years for females. The results of this study may indicate a latitudinal pattern in size and growth, with individuals from the eastern Bering Sea growing more slowly and reaching higher maximum ages than previously reported for specimens collected off the western coast of the United States.
0273 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Walter Bubley1, Paul Tsang1, David Koester2, James Sulikowski2
1University of New Hampshire, Durham, NH, United States, 2University of New England, Biddeford, ME, United States
A Reassessment of Spiny Dogfish, Squalus acanthias, Reproductive Parameters Following Increased Fishing Pressure in the Northwest Atlantic
Spiny dogfish (Squalus acanthias) are considered the most abundant shark species in theNorthwest Atlantic, but recent concerns regarding population size argue for updating their life history parameters. The last comprehensive study conducted on spiny dogfish in the Northwest Atlantic was over 20 years ago and prior to increased fishing pressure. A recent study examining fecundity in response to this fishing pressure observed a decrease in the median size of females at maturity as well as the size at first maturity using gross morphological criteria. One goal of our present study was to conduct a more complete examination of reproductive parameters of spiny dogfish in the Northwest Atlantic, using hormonal and histological assessments, as well as morphological observations. Blood and gonads were collected monthly from spiny dogfish from July 2006 – February 2009. Gross morphological parameters of reproduction were measured, including gonad weight for both sexes, ovarian follicle number and size, as well as pup number and size for females, with clasper length and calcification for males. Testes were processed and stained histologically to examine spermatogenesis. Plasma testosterone, estradiol, and progesterone concentrations were quantified using specific radioimmunoassays. The results showed changes in regards to size and age at maturity, fecundity and hormone concentrations, when compared to studies prior to the increased fishing pressure. By examining spiny dogfish reproductive parameters using a combination of histological, hormonal, and morphological endpoints, they provide a more accurate and higher resolution assessment of maturity and seasonality, which can be incorporated into fishery management plans.
0334 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Anabela Maia, Cheryl Wilga
University of Rhode Island, Kingston, RI, United States
Comparative Anatomy of Bamboo Shark and Spiny Dogfish Dorsal Fins
The dorsal fin anatomy of benthic white-spotted bamboo sharks Chiloscyllium plagiosum and benthopelagic spiny dogfish Squalus acanthias reflects their swimming habits. Differences are apparent in external and internal anatomy. Bamboo sharks have a larger second dorsal fin area and proportionally more muscle extending into both dorsal fins than spiny dogfish. Skeletal elements are composed of a variable number of basals and radials that are almost indistinguishable and lack a clear arrangement in spiny dogfish. In contrast, bamboo sharks have a single row of multiple plate-like elongated basals followed by a row of shorter radials that fans out into the fin web. Between each basal and radial lays a cartilaginous pad, indicating a movable joint. Bamboo fin muscle bundles are discrete and correspond with the radials. Spiny dogfish fin muscles have a more compact structure and lack discrete bundles. Dorsal fin complexity in spiny dogfish is increased by the presence of an anterior spine. The spines are wrapped in thick collagen fibers pointing posteriorly, which insert into the skin near the middle portion of the fin base. Similar bundles of collagen fibers run in the opposite orientation from the middle to the end of the fin base. The collagen fibers appear to make the fin more rigid but also create bending planes in the middle of the fin. Dorsal fin bending in dogfish may play a role in stabilizing forces, while the complex structure of bamboo shark fins imparts g
0048 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Austin Gallagher1, Lorenz Frick2, Peter Bushnell3, John Mandelman4
1Three Seas Program, Northeastern University, Boston, MA, United States, 2Monash University, Clayton, Victoria, Australia, 3Indiana University South Bend, Southbend, IN, United States, 4Edgerton Research Laboratory, New England Aquarium, Boston, MA, United States
Blood Gas, Oxygen Saturation, pH, and Lactate Values in Elasmobranch Blood Measured with an i-STAT® Portable Clinical Analyzer and Standard Laboratory Instruments
Assessments of the physiological response to different acute stressors are now being used to facilitate management decisions and conservation initiatives related to various fish species. Blood gas, pH, and blood lactate have been employed to ascertain condition and possibly post-release mortality in fishes, but data are often the most useful when collected immediately after individuals are captured. Portable clinical analyzers are now available that allow measurements to be made easily in the field. However, these instruments are designed for use with mammals use and therefore conduct measurements at 37°C. A few studies have validated the use of portable clinical analyzers for assessing blood gases and acid-base profiles in teleosts, but equivalent data are not available for elasmobranchs. We therefore examined the relationship of blood gas, pH, and lactate values measured with an i-STAT® portable clinical analyzer with those measured using standard laboratory blood gas (thermostatted to 25°C) and lactate analyzers using samples taken from three species of sharks. We found tight correlations (r2 > 0.90) and between pH, pO2, pCO2, oxygen saturation, and lactate level values generated by the portable clinical and laboratory instruments. We thus developed equations for converting blood values measured in elasmobranchs with an i-STAT® portable clinical analyzer to those taken at 25°C. Additional studies need to address a wider range of temperatures and elamobranch species, as it has been shown convincingly that the elasmobranch stress responses are highly variable interspecifically.
0590 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Jonathan Dale1, Natalie Wallsgrove2, Brian Popp2, Kim Holland1
1Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, HI, United States, 2University of Hawaii at Manoa, Honolulu, HI, United States
Ontogenetic Dietary and Habitat Shifts in Brown Stingrays (Dasyatis lata) in Hawai‘i Inferred from Stomach Content and Stable Isotope Analysis
Elasmobranchs may regulate ecological communities through a variety of density and trait mediated interactions. Stomach content and stable isotope analysis were used to assess the diet and habitat use of brown stingrays (Dasyatis lata), and to examine the possibility of competitive interactions with juvenile hammerhead sharks (Sphyrna lewini) in Kāne‘ohe Bay. Stingrays fed almost exclusively on crustaceans, with shrimps and crabs making the greatest contributions to the diet. An ontogenetic shift in stingray diet was consistent with positive relationships between stingray size and both δ15N and δ13C values. A dramatic decrease in bulk δ15N and δ13C was evident for large stingrays, which corresponded with the onset of sexual maturity. To test the hypothesis that the observed decrease represented a habitat shift from bay to offshore waters, δ15N values of individual amino acids were determined. The trophic level of stingrays increased with size independent of bulk δ15N values, indicating that differences in source δ15N between habitats were responsible for the decrease in bulk δ15N. There were low levels of dietary overlap between stingrays and hammerheads, due to a larger contribution of teleosts in the hammerhead diet. Hammerheads were also depleted in δ13C and enriched in δ15N relative to stingrays, suggesting that primary carbon sources differ between these two species and hammerheads feed at a higher trophic level. The combined analyses indicate that Kāne‘ohe Bay is an important juvenile habitat for brown stingrays, and suggest strong dietary resource partitioning between these two sympatric elasmobranch species.
0750 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Andrew Nosal1, Nicholas Wegner1, Daniel Cartamil1, Edward Kisfaludy1, Mark Royer2, Marcus Taylor3, Jeffrey Graham1
1Scripps Institution of Oceanography, La Jolla, California, United States, 2University of North Carolina – Wilmington, Wilmington, North Carolina, United States, 3University of Hawai’i – Hilo, Hilo, Hawai’i, United States
Movement Patterns of Leopard Sharks (Triakis semifasciata) along the Open Coast of San Diego County, California
Each year, hundreds of leopard sharks (Triakis semifasciata) aggregate in shallow waters at the head of La Jolla Submarine Canyon at the southern end of La Jolla Shores Beach. Despite growing public interest and the thriving eco-tourism industry surrounding “Leopard Shark City,” the ecological significance of this phenomenon and its underlying mechanisms remain poorly understood. Work to date indicates these sharks are mostly pregnant females, with no males and very few juveniles observed. The males aggregate 12 km north in deeper waters off Del Mar, CA, just inshore of a small kelp forest. In July 2009, 12 females (in La Jolla) and 10 males (in Del Mar) were surgically implanted with coded acoustic transmitters and monitored by a coastal receiver array spanning from Del Mar, CA to the USA-Mexico border. Both sexes exhibit strong fidelity to their respective capture sites, often dispersing at night. Active tracking shows females travel up to 1.5 km offshore at night and make sustained dives to >50 m. Some nights when aggregating females did not disperse coincided with California grunion runs. In early autumn, half of the passively tracked females departed northward along the coast, surpassing the northernmost receiver in Del Mar. One shark was captured 70 km north off San Clemente Pier. The remaining sharks departed southward around
Thanksgiving, following a string of leopard shark killings by a bull California sea lion. A portion of these sharks is expected to return in 2010. Males continue to be detected intermittently in the Del Mar vicinity.
0175 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Danielle Knip1, Michelle Heupel2, Colin Simpfendorfer1, James Moloney2, Andrew Tobin1
1Fishing and Fisheries Research Centre, School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia, 2School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia
Site Fidelity and Habitat Use of Spottail Sharks (Carcharhinus sorrah) in a Tropical Nearshore Environment
Tropical nearshore environments contain regions of high productivity and often provide key habitat for many shark populations. This project examines the presence and movements of shark species in a nearshore region to define their use of space and dependence on coastal habitats. An array of fifty-six acoustic receivers deployed in Cleveland Bay, north Queensland was used to monitor sharks within a tropical nearshore environment. Thirty spottail sharks (Carcharhinus sorrah) fitted with acoustic transmitters were monitored in 2009 and 2010. Spottail sharks displayed long-term use of this nearshore environment with some individuals continually present for more than 100 days. Individuals that remained within Cleveland Bay showed high levels of site fidelity to specific regions and consistent patterns were found in their use of space. Location of home ranges and distribution of spottail sharks within Cleveland Bay revealed segregation among individuals with some differences in behaviour between sexes. Spottail sharks are an important component of the commercial fishery in Queensland. Long-term presence and consistent use of nearshore regions suggests that Marine Protected Areas employed in these areas may provide some shelter from exploitation for spottail sharks. This research gives new insight into habitat use of spottail sharks and provides advice for potential management of these populations.
0333 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
David Kacev1, Rebecca Lewison1, Andrew Bohonak1, Daniel Cartamil3, John Hyde4, Russ Vetter4, Kevin Feldheim2
1San Diego State University, San Diego, CA, United States, 2Field Museum, Chicago, IL, United States, 3University of California, San Diego, La Jolla, CA, United States, 4South West Fisheries Science Center, La Jolla, CA, United States
Exploring the Benefits of Spatial/Landscape Genetic Analysis in Shark Populations
Historically, many genetic studies have relied on standard F-statistics or appropriate analogs such as Φst to delineate population boundaries, and functionally interpret divergence among populations. Over the past decade, a variety of spatial and landscape genetic analyses have been developed that can provide a more accurate interpretation of current and historical biological processes. I will use isolation by distance (Euclidean and least cost path), isolation by resistance, various population assignment, and Bayesian population inference analyses on genetic data from coastal shark species. I will then compare these results with those from traditional F-statistics. These new analyses have the potential to broaden our understanding of connectivity and stock structure in shark populations. This additional information will help better inform population assessment analyses and provide utility in informing more effective management.
0570 AES GRUBER AWARD, 551 AB, Friday 9 July 2010
Mae Taylor, Harold Laubach, David Kerstetter
Nova Southeastern University, Dania Beach, FL, United States
Spiral Valve Parasites of Selected Tropical Pelagic Elasmobranchs from the Western North Atlantic Ocean
Concerns regarding population status of many elasmobranchs have prompted investigations into less obvious sources of declines, such as morbidity due to parasites. Endoparasite (internal) loads in the elasmobranch spiral valve may be a source of such unaccounted mortality and morbidity by both inhibiting nutrient uptake and stimulating inflammatory responses within the gastrointestinal tract in the host. Spiral valves of the night shark (Carcharhinus signatus, n=16), silky shark (Carcharias falciformis, n=18) and pelagic stingray (Pteroplatytrygon violacea, n=99) were obtained opportunistically from pelagic longline operations. Each species had varying rates of parasitization: pelagic stingray 29%, silky shark 77%, and night shark 92%. Total spiral valve parasite loads were compared against the total length, weight and sex of the host; however, no relationship was observed between these factors. A total of 133 elasmobranch hosts were examined, yielding over 800 individual parasites. The majority of parasites were cestodes (92% pelagic stingray, 93% silky, 99% night), although trematodes (5% pelagic stingray, 2% silky, 1% night), nematodes (1% silky), and acanthacephalans (3% pelagic stingray and 4% silky) were also represented throughout the samples. There are over ten families of cestodes represented throughout the samples, two families of trematodes, one family of nematode and two families of acanthacephalans. Site specification was not examined for this research. Parasites were not shown to be host specific. These results establish baseline values for expected spiral valve parasite load and species compositions for pelagic shark and stingray hosts.
0250 AES Conservation & Management, 552 AB, Friday 9 July 2010
Ivy Baremore, Lori Hale
NOAA Fisheries Service, Panama City, FL, United States
Reproductive Patterns and Maturity Estimates of the Sandbar Shark Carcharhinus plumbeus in the US Atlantic Ocean and Gulf of Mexico
Sandbar sharks Carcharhinus plumbeus were sampled for age, growth, and reproduction from January 2007 – February 2010. Samples were collected by fisheries observers aboard commercial longline fishing vessels, and age and reproductive parameters were assessed by biologists at the NOAA Fisheries Service Panama City Laboratory. All sandbar sharks examined for reproductive analysis were directly aged using vertebral band counts (n=1100). Size and age at 50% maturity were determined for females and males using logistic regression analysis, and size at which 50% of females were in maternal condition was also calculated. Seasonality of reproduction was determined from monthly plotting of measurements of the reproductive tract (gonads, oocytes, etc.) from mature animals. Mature females and males were staged according to reproductive condition to further elucidate seasonality and periodicity. Embryo length was plotted by month to determine the length of gestation and time of parturition. Sex ratio of embryos from all females was tested for significant difference from a 1:1 ratio with a χ2 test. Finally, a regression of female length was plotted against number of embryos per female to assess whether fecundity increased with increasing maternal length.
0253 AES Conservation & Management, 552 AB, Friday 9 July 2010
Loraine Hale, Ivy Baremore
NOAA Fisheries, Panama City, FL, United States
Age and Growth Estimates of the Sandbar Shark Carcharhinus plumbeus in the US Atlantic Ocean and Gulf of Mexico
Sandbar sharks, Carcharhinus plumbeus, were sampled for age, growth, and reproduction from January 2007 – February 2010 by fisheries observers onboard commercial longline vessels. Sharks ranged in size from 39 cm fork length to 202 cm fork length, with an average size of 152 cm. All sandbar sharks were independently and directly aged by two readers using vertebral band counts (n=1245). Annual periodicity of growth bands has previously been validated. Ages were examined for precision and bias within and between readers. Growth curves including the von Bertalanffy growth curve, a modified two-parameter von Bertalanffy growth curve, and a Gompertz growth curve were derived from consensus counts of vertebral band counts and compared to find the model with the best fit to the data. Size selectivity of the gear was assessed and the growth estimates were used in stock assessment models for the species.
0639 AES Conservation & Management, 552 AB, Friday 9 July 2010
S. R. Sagarese, M. G. Frisk
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, United States
An Investigation on the Effect of Photoperiod and Temperature on Vertebral Band Deposition in Little Skate, Leucoraja erinacea
An investigation was undertaken to determine whether photoperiod or temperature have an effect on the timing of vertebral band pair deposition in captive young-of-the- year (YOY) little skate, Leucoraja erinacea. The experimental design consisted of a randomized complete block split plot design with two factors: temperature and light. Temperature was nested within light and therefore four variables were tested: (1) constant light, (2) constant temperature, (3) seasonal light, and (4) seasonal temperature. For 18 months, little skate experienced accelerated seasonal conditions of temperature and light to mimic 3 years of growth. This study provides primary and supporting evidence that seasonal photoperiod and temperature, respectively, have no effect on timing of vertebral band pair deposition in captive little skate. Vertebral analysis of seven surviving skates showed that all produced 1 to 1.5 band pairs regardless of treatment over 18 months. Centrum edge analysis of 56 specimens provided evidence that the timing of winter and summer band deposition was not affected by treatments. The winter band (translucent) appeared in February 2007 and January 2008 while the summer band (opaque) showed up in July for both 2007 and 2008 and mimicked patterns observed in the wild. While temperature and photoperiod appear to have no effect on timing of band pair deposition in YOY little skate, other mechanisms which may influence band deposition should be investigated including the effect of food ration and the presence of a circa-annual rhythm and/or hormone secretion.
he Use of Oxytetracyline Marked Vertebrae to Validate Age Determination of Winter Skate (Leucoraja o MISSING!!!
0431 AES Conservation & Management, 552 AB, Friday 9 July 2010
Christine Ward-Paige1, Camilo Mora1, Heike K. Lotze1, Christy Pattengill- Semmens2, Loren McClenachan3, Ery Arias-Castro3, Ransom A. Myers3
1Dalhousie University, Halifax, NS, Canada, 2Reef Environmental Education Foundation, Key Largo, FL, United States, 3University of California, San Diego, CA, United States
Patterns of Shark Occurrence on Reefs in the Greater-Caribbean: A Footprint of Human Exploitation
Recent studies have documented dramatic declines in large coastal and pelagic shark populations which have been attributed to commercial fishing. However, the status of sharks in other systems such as coral reefs remains unexplored despite a long history of exploitation. We explored the contemporary distribution and sighting frequency patterns of sharks on reefs in the greater-Caribbean and assessed the possible role of human exploitation on such patterns. Historical records, range maps, and habitat suitability models indicate that sharks should be widely distributed and common throughout the greater-Caribbean. However, analysis of 76,340 underwater surveys show that sharks are largely absent on contemporary reefs; a pattern that was more pronounced with the exclusion of nurse sharks. Comparison with human population showed that, with the exception of nurse sharks, sharks occur most often in areas with low human population or where marine conservation exists. Population viability analysis suggest that the absence of sharks in the presence of humans can be explained by exploitation alone, since we found that sharks are vulnerable to even light levels of fishing pressure. Our results show that under current levels of fishing mortality even the most productive sharks are at risk. Our findings indicate that preventing the loss of sharks on reefs in the greater-Caribbean requires urgent management measures to protect sites where sharks still exist. The fact that sharks still occur in a few densely populated areas where strong fishing regulations are in place indicates the possibility of success and encourages the implementation of conservation measures.
0071 AES Conservation & Management, 552 AB, Friday 9 July 2010
Enric Cortes1, Megan Winton1
1NOAA / NMFS, Panama City, FL, United States, 2Moss Landing Marine Laboratories, Moss Landing, CA, United States
Predicting the Global Vulnerability of Sharks to Habitat Loss
Recent risk assessment approaches (Productivity and Susceptibility Analyses) have focused on evaluating the vulnerability of stocks of sharks and other fishes to the effect of fishing. We modified a model previously applied to birds and lemurs to assess the global vulnerability of a suite of shark species to habitat loss. We used dietary, habitat and distribution information to calculate a range size index (RSI) and a habitat loss specialization index (HLSI) that combined habitat and dietary specialization measures. We used the number of reported FAO regions occupied by a species as a measure of its range. The HLSI was computed as the product of dietary specialization (D) and habitat specialization (H). Dietary specialization was calculated with Levin’s standardized measure of dietary breadth based on updated standardized diet composition information that summarizes quantitative studies using an average weighted by sample size in each study. Habitat specialization was ranked on a scale linked to the diversity of up to ten identified habitat types used by each species. We then plotted HLSI against RSI, computed global vulnerability based on Euclidean distance, and ranked the global vulnerability of all species analyzed. The values we obtained should be interpreted as indicative of global vulnerability of shark species to habitat loss; however, similar analyses with more detailed information could be conducted at smaller spatial scales. This rapid-assessment technique based on basic biological information predicts the relative vulnerability of species to habitat loss and thus can be useful for identifying species of potentially greater conservation concern.
0305 AES Conservation & Management, 552 AB, Friday 9 July 2010
Karyl Brewster-Geisz, LeAnn Hogan, Jacqueline Wilson, Peter Cooper, Joe Desfosse, Guy DuBeck, Steve Durkee, Richard Hall, Margo Schulze-Haugen, George Silva
NOAA/NMFS, Silver Spring, MD, United States
Status of Atlantic Shark Management in the United States
The Highly Migratory Species (HMS) Management Division of the National Marine Fisheries Service (NMFS) is responsible for the management of the U.S. federal shark fisheries in the Atlantic Ocean including the Gulf of Mexico and Caribbean Sea. Over the past few years, there have been numerous changes in how the shark fisheries are managed, which have required changes to the fishery management plan (FMP). In July 2008, NMFS implemented new management measures in the Atlantic shark fisheries, including a requirement that all sharks be landed with fins naturally attached and the creation of a small shark research fishery focusing on the sandbar shark (Carcharhinus plumbeus). Based on recent stock assessments, NMFS released Draft Amendment 3 to the Consolidated HMS FMP in July 2009. Under the Draft Amendment 3, management measures were proposed that would implement measures to rebuild blacknose sharks (C. acronotus), end overfishing of shortfin mako (Isurus oxyrinchus) and blacknose sharks, and establish federal management of smooth dogfish (Mustelus canis). The final management measures for Amendment 3 are expected to publish in late spring 2010. NMFS will continue to update management measures, as needed, based in part on shark stock assessments.
0203 AES Conservation & Management, 552 AB, Friday 9 July 2010
Alexia Morgan1, Mike Allen1, Enric Cortés2, Colin Simpfendorfer3, George Burgess1
1University of Florida, Gainesville, Fl, United States, 2NOAA/NMFS, Panama City, FL, United States, 3James Cook University, Townsville, Queensland, Australia
Population Assessment of the Dusky Shark in the Western North Atlantic Ocean Using an Age-structured Model
An age-structured model was used to assess the effects of fishing on population trends for the dusky shark (Carcharhinus obscurus) off the east coast of the USA. This model included age-specific vulnerability to fishing, maturity and growth schedules, and a Beverton and Holt stock recruit equation. Results of the base case-scenarios, and sensitivity analyses indicated that the population of dusky sharks in the western North Atlantic Ocean is between 9 and 50% of virgin biomass in 2006. Model results showed that the impacts of fishing already imposed on the dusky shark combined with the continued bycatch of this species, will be difficult to overcome even with the implementation of time/area closures, gear modifications and/or catch and discards being reduced for another 20 years. Recent publications have shown that the Maximum Sustainable Yield (MSY) for dusky sharks may be well above 50% of the virgin biomass, suggesting this species is currently overfished even in the most optimistic scenarios, and will require long-term targets for recovery to sustainable levels.
0386 AES Conservation & Management, 552 AB, Friday 9 July 2010
John Froeschke1, Gregory Stunz1, Blair Sterba-Boatwright1, Mark Wildhaber1
1Gulf of Mexico Fishery Management Council, Tampa FL, United States, 2Texas A&M University-Corpus Christi, Corpus Christi TX, United States, 3Texas A&M University- Corpus Christi, Corpus Christi TX, United States, 4U.S. Geological Survey, Columbia MO, United States
Testing the Shark Nursery Area Concept in Texas Bays Using a Long-term Fisheries-Independent Dataset
Using a long-term fisheries independent dataset, we experimentally tested the “shark nursery area concept” recently proposed by Heupel et al. (2007). We used the suggested working assumptions that juvenile shark nursery habitat would: 1) have an abundance of juveniles greater than the mean abundance across all habitats where they occur; 2) use same areas repeatedly through time (years); and 3) remain within the habitat for extended periods of time. We tested this concept using young-of-the-year (Age 0) and juvenile (Age 1+) bull sharks (Carcharhinus leucas) from gill-net surveys conducted in Texas estuaries from 1976-2006 to determine the nursery function of nine coastal estuaries. Of the nine bay systems considered for primary bull shark nursery habitat, only Matagorda Bay satisfied all three criteria for both cohorts. Both San Antonio and Matagorda Bays satisfied the criteria as nursery habitat for juveniles. Through these analyses we identified the utility of this approaching for characterizing nursery areas. We also note some practical considerations, such as of the influence temporal or spatial scales of the study when applying the nursery role concept to shark populations.
0647 AES Conservation & Management, 552 AB, Friday 9 July 2010
M.G. Frisk1, T.J. Miller2, K. Sosebee3, J. Musick4, P. Rago1
1School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, United States, 2Chesapeake Biological Laboratory, University of Maryland Center for Environmental, Solomons, MD, United States, 3Northeast Fisheries Science Center, National Marine Fisheries Service, Woods Hole, MA, United States, 4Virginia Institute of Marine Science, Gloucester Point, VA, United States
Adult, Juvenile and Neonate Habitat Preferences of Spiny Dogfish, Squalus acanthias: Density, Temperature and Neonate Range Expansion in the Western Atlantic
We present analyses of the movement, distribution and habitat preference of spiny dogfish, Squalus acanthias, from Cape Hatteras to the Gulf of Maine based on data collected by the National Marine Fisheries Service during annual autumn and spring bottom trawl surveys (1963-2006). Cumulative distribution functions (CDF) were utilized to estimate temperature and depth preferences of spiny dogfish neonates, juveniles and mature females. Neonate, juvenile and adult spiny dogfish selected significantly narrower ranges of temperatures than available in the environment and significantly different from each other. Younger stages selected warmer waters than older stages during both the spring and fall (Spring: 50th percentile of neonate dogfish distribution was 10.3○C, 9.3 ○C for female juveniles and 8.0 ○C for adult females, Fall: 50th percentile of neonate dogfish was 12.4 ○C, 12.2 ○C for juveniles and 11 ○C for mature females. Further, neonate range appears to have expanded onto the eastern edge of Georges Bank and into the eastern portion of the Gulf of Maine during periods of high spiny dogfish abundance in the 1980’s. However, in recent years spiny dogfish still occupy this expanded range even after the population has declined. We explore the potential of the interaction between population size and environmental changes influencing range expansion, contraction and overall distribution of spiny dogfish.
0032 AES Conservation & Management, 552 AB, Friday 9 July 2010
Tonya Wiley1, Shelley Norton2, John Carlson3, Amanda Frick2
1Texas Parks and Wildlife Department, Coastal Fisheries Division, Dickinson, Texas, United States, 2NOAA Fisheries Service, Southeast Regional Office, Protected Resources Division, St. Petersburg, Florida, United States, 3NOAA Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, Florida, United States
Designating Critical Habitat for the Endangered Smalltooth Sawfish Pristis pectinata in the United States: Challenges and Results
On April 1, 2003, the U.S. distinct population segment (DPS) of smalltooth sawfish (Pristis pectinata) was listed as endangered by NOAA Fisheries Service. At the time of listing, very little information was known about the habitat usage patterns for this species; therefore, critical habitat could not be determined. Following the listing studies necessary for the identification of specific habitats and environmental features important for the conservation of the species were conducted. Facilitating recruitment into the adult population by protecting the species’ juvenile nursery areas was identified as the key conservation objective for the species that would be supported by the designation of critical habitat. The location of potential nursery areas was determined through applying a model developed for identifying elasmobranch nursery areas to smalltooth sawfish encounter data. The habitat features essential to the conservation of the species (also known as the essential features) were identified as red mangroves and shallow euryhaline habitats characterized by water depths less than ~ 1.0 m. These essential features are necessary to facilitate recruitment of juveniles into the adult population by providing for potential predator avoidance and habitat for prey. Two specific areas located along the southwestern coast of Florida between Charlotte Harbor and Florida Bay which contain nurseries and the essential features were designated as Critical Habitat. The Charlotte Harbor Estuary Unit comprises approximately 221,459 acres (346 mi2) of coastal habitat; and the Ten Thousand Islands/Everglades Unit (TTI/E) comprises approximately 619,013 acres (967 mi2) of coastal habitat.
0316 AES Conservation & Management, 552 AB, Friday 9 July 2010
Eric Hoffmayer1, James Franks1, Jennifer McKinney1, Jill Hendon1, William Driggers III2
1The University of Southern Mississippi/Gulf Coast Research Laboratory, Ocean Springs, MS, United States, 2NOAA Fisheries, Mississippi Laboratories, Pascagoula, MS, United States
Advances in Whale Shark (Rhincodon typus) Research in the Northern Gulf of Mexico
Reports of whale sharks, Rhincodon typus, in the northern Gulf of Mexico date back to the 1930’s; however, few studies have provided information beyond observational accounts. To address the lack of knowledge pertaining to the biology, distribution and movements of whale sharks in the western North Atlantic Ocean, the University of Southern Mississippi’s Gulf Coast Research Laboratory initiated the Northern Gulf of Mexico Whale Shark Research Program in 2003. One of the program’s primary objectives is to document the distribution of whale sharks in the northern Gulf of Mexico in collaboration with fishermen, helicopter pilots, offshore petroleum industry personnel and other researchers. To date, over 300 whale shark sightings have been recorded with approximately one third of those sightings relating to aggregations of up to 200 individuals. This research has revealed that whale sharks are relatively abundant in the northern Gulf of Mexico and their seasonal occurrence is highly predictable. Additionally, satellite tagging data and photo identifications have established connectivity between whale sharks in the northern Gulf of Mexico and the Caribbean Sea. The purpose of this presentation is to discuss what is now known about whale sharks in the northern Gulf of Mexico, current research efforts, and future directions of our study of these sharks.
0715 AES Conservation & Management, 552 AB, Friday 9 July 2010
Daniel Cartamil1, Omar Santana-Morales2, Miguel Escobedo-Olvera2, Dovi Kacev4, Leonardo Castillo-Geniz3, Oscar Sosa-Nishizaki2, Jeffrey Graham1
1Scripps Institution of Oceanography, La Jolla, CA, United States, 2Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, Mexico, 3Centro Regional de Investigación Pesquera de Ensenada, Ensenada, Baja California, Mexico, 4San Diego State University, San Diego, CA, United States
The Artisanal Elasmobranch Fishery of the Pacific Coast of Baja California, Mexico
Artisanal fisheries account for up to 80% of elasmobranch fishing activity in Mexican waters, yet details associated with fishing effort and species composition are generally unavailable. This chapter describes a survey of the artisanal elasmobranch fishery of the Pacific coast of Baja California, Mexico from 2006 – 2008. The objectives were to determine the geographical extent, size, and targets of the artisanal fishery, and describe the catch characteristics at Laguna Manuela, a representative artisanal camp where elasmobranchs are the primary target. Forty-four fishing sites were identified in the region, of which 29 (66%) targeted elasmobranchs at least seasonally, using primarily bottom-set gillnets and longlines. At Laguna Manuela, 25 species of elasmobranchs were documented. Gillnetting accounted for 60% of fishing effort, and the most commonly captured species were Rhinobatos productus, Zapteryx exasperata, and Myliobatis californica. Longline fishing accounted for 31% of fishing effort, and the most commonly captured species were Prionace glauca and Isurus oxyrhinchus. Catch was composed of mainly juveniles for many species, suggesting that the immediately surrounding area (Bahia Sebastian Vizcaino) may be an important elasmobranch nursery habitat. The results of this study will serve as a valuable baseline to determine future changes in the artisanal fishery, as well as changes in species demography and abundance.
0782 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
James Sulikowski1, Ben Galuardi2, Walter Bubley2, William Driggers4, Eric Hoffmayer3, Angela Cicia1, Paul Tsang2
1University of New England, Biddeford, ME, United States, 2University of New Hampshire, Durham, NH, United States, 3Gulf Coast Research Laboratory, Ocean Springs, MS, United States, 4National Marine Fisheries Service, Pascagoula, MS, United States
Dismissing Dogma? What Do We Really Know About the Spiny Dogfish, Squalus acanthias, Population in the U.S. Portion of the Western North Atlantic Ocean
The status of the spiny dogfish, Squalus acanthias, stock in the U.S. portion of the northwest Atlantic has become a contentious issue. Distributed from Maine to Florida, this species was once considered to be the most abundant shark throughout it’s U.S. range. As a result of reported declines below biomass threshold levels, in early 2000 the Mid-Atlantic, New England Fishery Management Councils, and Atlantic States Marine Fisheries Commission implemented a management plan which imposed annual quotas and possession limits for vessels fishing in both federal and state waters. Due to such characteristics as slow growth, extended gestation period, small litter size, and a spawning stock biomass (SSB) below threshold levels as recent as 2005, the spiny dogfish population was not anticipated to rebound for more than a decade. However, recent Northeast Fishery Science Center (NEFSC) survey data suggest a four-fold increase in SSB has occurred between 2005-2009. Based on the aforementioned life history characteristics, this substantial increase in biomass is considered biologically unrealistic. We present preliminary data to support hypotheses’ that are divergent to common paradigms: 1) we hypothesize that the biological unrealistic increases in SSB may be due, in part, to a substantially more active vertical movement pattern that prevents this species from being effectively captured by NEFSC otter trawl surveys; and 2) we hypothesize that the gestation period of spiny dogfish may be less than the proposed 22 months and that there may also be regionally different reproductive cycles across this species U.S range.
0613 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Jennifer Cudney, Roger Rulifson
East Carolina University, Greenville, NC, United States
Elucidating the Behavior of Spiny Dogfish (Squalus acanthias) that Overwinter in Coastal North Carolina Waters with Acoustic Telemetry Methodologies
The management of spiny dogfish sharks (Squalus acanthias) is highly controversial in North Carolina. Participants and industry representatives across the entire eastern US coast claim that current state and federal survey efforts are not adequate to describe the complex behaviors and general abundance of dogfish. A comprehensive understanding of movement and migration patterns is a critical component of validating current survey methods. Previous mark-recapture research has identified separate behavioral contingents of spiny dogfish, and a “mid-Atlantic contingent” that exhibits a general north-south migration pattern between North Carolina and Cape Cod. The purpose of this research is to use acoustic telemetry technology to further characterize the behavior of spiny dogfish that overwinter in North Carolina. In 2009 and 2010, 90 spiny dogfish were tagged with Vemco V-16 acoustic transmitters. VR2W acoustic receivers were moored just south of Cape Hatteras, NC. Mobile tracking surveys were conducted between Oregon Inlet, NC and Ocracoke Inlet in February and March of 2009 and 2010. In 2009, 7 spiny dogfish were detected on the VR2W receivers and 6 were detected using mobile tracking surveys. Data collection in 2010 is ongoing. Supplementary fishery independent data, satellite sea surface temperature (SST) data, tide data, and acoustic dopplar current profiler (ADCP) data were compared to movement data to identify environmental factors that influence behavior.
0251 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Jeff Kneebone1, Gregory Skomal2, John Chisholm2
1University of Massachusetts Dartmouth; School for Marine Science and Technology, New Bedford, Massachusetts, United States, 2Massachusetts Division of Marine Fisheries, New Bedford, Massachusetts, United States
Spatial and Temporal Habitat Use and Movement Patterns of Neonatal and Juvenile Sand Tiger Sharks, Carcharias taurus, in a Massachusetts Estuary
In recent years, an increasing number of neonate and juvenile sand tiger sharks (Carcharias taurus) have been incidentally taken by fishermen in Plymouth, Kingston, Duxbury (PKD) Bay, a 10,200 acre tidal estuary located on the south shore of Massachusetts. There are indications that the strong seasonal presence (late spring to early fall) of sand tigers in this area is a relatively new phenomenon as local fishermen claim that they had never seen this species in large numbers until recently. We utilized passive acoustic telemetry to monitor seasonal residency, habitat use, site fidelity, and fine scale movements of 35 sand tigers (79 – 120 cm fork length; age 0 – 1) in PKD Bay. Sharks were tracked within PKD Bay for periods of 5 – 88 days during September – October, 2008 and June – October, 2009. All movement data are currently being analyzed to quantify spatial and temporal habitat use, however, preliminary analyses suggest that sharks display a high degree of site fidelity to several areas of PKD Bay. Outside PKD Bay, we documented broader regional movements throughout New England. Collectively, these data demonstrate the that both PKD Bay and New England coastal waters serve as nursery and essential fish habitat (EFH) for neonatal and juvenile sand tiger sharks.
0335 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Hans Walters1, Ramón Bonfil4, John Morrissey2, Dennis Thoney3
1Wildlife Conservation Society/New York Aquarium, Brooklyn, New York, United States, 2Sweet Briar College, Sweet Briar, Virginia, United States, 3Vancouver Aquarium, Vancouver, British Columbia, Canada, 4Shark Tracker/NABU, Brooklyn, NY, United States
Movements of Sand Tiger Sharks (Carcharias taurus) in the Northwest Atlantic Ocean
From 2003-2006, we attached pop-up satellite tags to 16 sand tiger sharks, Carcharias taurus, to study movements and habitat preferences in the northwest Atlantic Ocean. Ten tags deployed off South Carolina returned data from nine males and one female.
Tracks ranged from 29 – 184 days. Three tags jettisoned in state waters off New Jersey, Delaware, and Florida, respectively. Six tags jettisoned in U.S. Federal waters, and one transmitted east of the Exclusive Economic Zone. Depth data indicate several tags experienced significant drift; readings of < 0 meters were common, delaying transmissions after premature releases. Light levels enabled estimates of horizontal movements. Tag-manufacturer software provided crude location estimates, and the Kftrack program reduced location errors to produce Most Probable Tracks (MPTs) for four sharks. Males moved north after tagging, but remained off North Carolina until July before continuing northward. Three sharks moved offshore, and one remained close to shore; we estimated swimming speeds of 0.27 – 2.24 km/hr. MPTs for two males indicated their presence off New Jersey and Delaware in late September and early October, respectively. A tagged female provided the only pop-up location south of the deployment area, from on or close to shore in northern Florida in late October. Sharks spent May and June at depths of ≤ 30 meters. Most moved into deeper waters of ≤ 152 meters as summer progressed, but one shark remained at shallow depths. Ambient temperatures may influence movements, as most sharks swam deeper in response to temperatures > 25° C.
0689 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Johanna Imhoff1, Jason Romine2, Chelsey Campbell1, George Burgess1
1Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, United States, 2Columbia River Research Laboratory, WFRC, USGS, Cook, WA, United States
Movements and Habitat Use of Juvenile Bull Sharks (Carcharhinus leucas) in the Indian River Lagoon System, FL, USA
The Indian River Lagoon System (IRL), Florida, USA, consisting of the Indian River, Banana River and Mosquito Lagoon, is known to be a nursery area for juvenile bull sharks (Carcharhinus leucas), but little is known about movements, habitat use, and residence time within this estuary. The northern Banana River is a refuge and closed to public access. We used passive acoustic telemetry methods to monitor the movements of juvenile bull sharks within this refuge and the adjoining IRL system. Since December 2008, 22 juvenile bull sharks (65-137 cm FL) have been tagged with Vemco V13 and V16T acoustic tags. Only one of the five sharks tagged in the refuge area has moved south out of the Banana River, into the Indian River proper. Once this animal entered Indian River it did not return to Banana River. Sharks that remained within the northern Banana River exhibited similar home range sizes. One of these sharks was found dead in February 2010 and is believed to have succumbed to unusually cold temperatures that occurred in January 2010. Sharks tagged in Indian River proper did not enter the Banana River and did not move north into Mosquito Lagoon. Three sharks tagged with V16T temperature sensing tags encountered temperatures of 18.7 – 25.2 oC with a mean of 21.7 oC.
0435 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Eric Reyier1, Bryan Franks2, Demian Chapman3, Steven Kessel2, Samuel Gruber2
1Kennedy Space Center Ecological Program / IHA Environmental Services, Kennedy Space Center, Florida, United States, 2Bimini Biological Field Station, Bimini, Bahamas, 3Stony Brook University, Stony Brook, New York, United States
Site Fidelity and Seasonal Movement Patterns of Juvenile Lemon Sharks in an Open Ocean Nursery at Cape Canaveral, Florida
For many coastal sharks, including the well studied lemon shark (Negaprion brevirostris), the geographic extent and temporal patterns of use in their winter nursery grounds remain poorly defined in most regions. Since 2003, we’ve documented large recurring winter aggregations of juvenile lemon sharks utilizing shallow surf zone habitats at Cape Canaveral, east-central Florida. To assess duration of residency within this open ocean nursery, as well as the timing of, and cues to, any coastal migrations, lemon sharks were implanted with acoustic transmitters in December 2008 (n = 9) and 2009 (n = 23). Fidelity to aggregation sites was monitored with up to 10 autonomous acoustic receivers while regional migrations were assessed via the Florida Atlantic Coast Telemetry (F.A.C.T.) Array, a network of 170 receivers spanning 300 km of the Florida east coast. Sharks released in December 2008 were regularly detected locally for up to 107 days. Five individuals were subsequently recorded on F.A.C.T. receivers 80 km north, confirming a northward spring migration as rapid as 18.1 km day-1. Behavior differed somewhat for 2009 releases with many sharks migrating south as far as West Palm Beach (190 km), apparently in response to a prolonged period of below average water temperature. Unexpectedly, 18 adult lemon sharks originally tagged from aggregations near Jupiter, Florida (175 km south) were also detected at Cape Canaveral in spring 2009 providing a putative connection between these two groups. Continued tracking over the coming year coupled with ongoing genetic analyses will further clarify the strength of this relationship.
0692 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Steven Kessel1, Samuel Gruber2, Todd Gedamke5, Bryan Franks3, Demian Chapman4, David Kerstetter6, David Fugate7, Rupert Perkins1
1Cardiff University, Cardiff, United Kingdom, 2University of Miami, Miami, Florida, United States, 3Bimini Biological Field Station, South Bimini, Bahamas, 4Stony Brook University, Stony Brook, New York, United States, 5National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida, United States, 6Nova Southeastern University, Dania Beach, Florida, United States, 7Florida Gulf Coast University, Fort Myers, Florida, United States
Influence of Water Temperature on Behaviour and Migration of Adult Lemon Shark (Negaprion brevirostris) Throughout the U.S. Eastern Seaboard
Large aggregating groups of adult lemon sharks (Negaprion brevirostris) are annually present off the coast of Jupiter, Florida, during the winter months. These aggregations are composed of individuals known to exhibit seasonal north – south migrations along U.S. eastern seaboard. Through a combination of passive acoustic telemetry, Pop-off Satellite Archival Tags (PSAT), temperature and current profilers, water temperature appeared to be the environmental cue correlated with the timing, duration and locations of many adult N. brevirostris seasonal behaviours. Adult N. brevirostris of the Jupiter aggregations appear to have a water temperature preference of ~23/24°C, which in turn determines the timing of the annual aggregation period and may well be the driving variable for both latitudinal and vertical depth movements. Archived depth and temperature profiles demonstrated that individual sharks adjusted their depth to remain in water with a temperature of ~24°C. Seasonal migrations north in the summer months and south in the winter months follow the annual changes in coastal water temperature, with the location of the winter aggregations in Jupiter located at the most southerly distribution of cooler water temperatures. Thermal preferences seem to dictate aggregating periods, latitudinal migrations, and vertical movements, indicating that temperature is a strong driving factor in both the annual and day to day distribution of mature N. brevirostris attending the seasonal aggregations.
0434 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Bradley Wetherbee1, Mahmood Shivji2, Guy Harvey3, Neil Burney4, Choy Aming4
1University of Rhode Island, Kingston, RI, United States, 2Nova Southeastern University and Guy Harvey Research Institute, Ft. Lauderdale, FL, United States, 3Guy Harvey Research Institute, Ft. Lauderdale, FL, United States, 4Bermuda Shark Project, Bermuda, Bermuda
Movements and Habitat Use of Tiger Sharks (Galeocerdo cuvier) Revealed by Tracking with Satellite Transmitters, the Bermuda-Bahamas Connection
Movements and habitat use of tiger sharks (Galeocerdo cuvier) vary among locations and describing behaviors that apply to major demographics the tiger shark populations is challenging. Tiger sharks are common inhabitants of deep reefs off Bermuda during summer months, but are thought to leave in fall and exhibit a seasonal movement cycle. We tagged tiger sharks in Bermuda in late summer with fin-mounted “spot” satellite transmitters (n=9) and archival popup satellite transmitters (n=7) to investigate movement patterns and habitat use of these sharks. Sharks generally remained near Bermuda until fall, when they made directed southeastern movements of 1-2 weeks duration and 1300-1700 km until reaching the Bahamas or Lesser Antilles. The sharks spent the winter months moving within relatively small areas, at times very close to shore. Several individuals exhibited more pelagic behavior remaining farther from shore in deep water. Sharks spent the majority of their time in the uppermost portion of the water column in water greater than 26oC. Monitoring of these sharks continues with the goal of documenting their movements as summer approaches with a possible return to Bermuda. Tiger sharks tagged in Bermuda demonstrate relatively consistent behavior occupying a northern summer habitat and migration to a southern wintering area over 1000 km distant. The results of our study support the contention that tiger sharks are highly mobile apex predators that connect widespread insular and pelagic habitats within the Western North Atlantic.
0768 AES Behavior & Ecology, 552 AB, Friday 9 July 2010
Lucy Howey1, Bradley Wetherbee2, Lance Jordan1, Mahmood Shivji1
1Nova Southeastern University, Guy Harvey Research Institute, Dania Beach, United States, 2University of Rhode Island, Kingston, RI, United States
Movement Patterns and Habitat Utilization of Blue Sharks (Prionace glauca) in the Northwest Atlantic as Determined by Pop-up Satellite Tags
Blue sharks (Prionace glauca) are among the most abundant and widely distributed of all oceanic elasmobranchs. The fragmentary nature of blue shark life history information, including movement and migratory behavior, continues to limit management efforts that require such data for stock assessment and sustainable catch modeling. To assist in obtaining a better understanding of blue shark movement in the northwest Atlantic, satellite telemetry was used to investigate habitat utilization and movements of individuals during the summer when the sharks form aggregations on the continental shelf off the Northeast United States, and during pelagic migrations. Thirty-one (26 male, 5 female) sharks were tagged with pop-up archival satellite transmitters. The transmitters reported data from a total of 1,656 combined days, yielding 74,163 depth and 74,125 temperature recordings. Tracked sharks exhibited two distinct movement patterns. During summer, the sharks remained within a restricted area south of Nantucket Island and occupied shallow depths (mean 8m). During fall, the sharks made directed offshore and southerly movements, with several sharks associating with waters east of Bermuda. During pelagic migrations, the sharks demonstrated markedly different habitat utilization, occupying much greater depths (mean 127m) and exhibiting clear diel depth patterns, not observed on the shelf. There were indications that the different demographic groups (immature females, mature and immature males) displayed different movement behavior. This study provides detailed information on habitat utilization and movement patterns of blue sharks in the northwest Atlantic, and underscores the need for further investigation of movement displayed by different demographic segments of the population.
0446 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
New College of Florida, Sarasota, Florida, United States
An Heuristic Model of the Neural Control of Feeding in Elasmobranchs
Considerable information has accrued in the past 20 years concerning sensory modalities (vision, mechanoreceptive and electroreceptive lateral line, olfaction, audition) involved in finding food in sharks and batoids. Comparative gross anatomical studies that correlate relative brain area development to feeding ecology provide suggestions of the relative importance of these modalities in various species. Differences relate to both phylogeny and habitat. Details on the processing mechanisms are less well understood but information on similar systems in teleosts and tetrapods can be used for inference. Localization of regions (telencephalon, optic tectum and cerebellum) concerned with multimodal sensory processing and cognitive functions that are likely involved in feeding have been identified and the complexity of their development parallels that of the fish’s behavior. Information on regions (hypothalamus, telencephalon) controlling appetite and motivation to search for food is available from a few brain stimulation studies in sharks and the mapping of central distributions of peptide hormones (neuropeptide Y, cholecystokinin, galanin, gonadotropin-releasing hormone II) involved in feeding activation in elasmobranches and/or other vertebrates.
A synthesis of information in these categories is summarized in a tentative model of overall feeding control.
0455 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Mason Dean1, Daniel Huber2, Joseph Bizzarro3, Lara Ferry-Graham4
1Max Planck Institute, Dept. Biomaterials, Potsdam, Germany, 2University of Tampa, Tampa, FL, United States, 3University of Washington, Seattle, WA, United States, 4Moss Landing Marine Laboratory, Moss Landing, CA, United States
Durophagy in Cartilaginous Fishes
Durophagy —typically defined as “the eating of hard prey”— is comparatively rare among the cartilaginous fishes, but has evolved at least once in each of the three major lineages. If we consider “hard” prey items to be those that require the removal of some mineralized, non-nutritious coating in order to be ingested or digested, then from a functional standpoint, durophagy is less about eating hard foods than dealing with hard structures that limit access to soft, nutritious ones. Here, we highlight the myriad independent evolutionary pathways and feeding mechanisms that have permitted access to this ecological niche in cartilaginous fishes. Although durophagous chondrichthyans apparently all employ a fracturing technique of exoskeleton destruction, the means of achieving the bite forces and skeletal reinforcements necessary for this mode of dealing with prey vary widely. Relative to non-durophagous species, hard-prey eaters exhibit any combination of modifications of skeletal material (tissue material properties), skeletal structure (cortical thickening, trabeculation, cross-sectional shape), dental morphology, cranial geometry (lever arms), muscular morphology (hypertrophication, fiber angle) and/or feeding behavior (winnowing, cyclic biting). Modifications to muscular physiology (fatigue-resistance, fiber type), and gastric structure and physiology may also exist in durophagous species; however, this has yet to be examined. In assembling the mechanisms of chondrichthyan durophagy, we outline the functional requirements and constraints on the feeding mechanism and highlight areas for future study.
0383 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Cheryl Wilga1, Ashley Stoehr1, Danielle Duquette2
1University of Rhode Island, Kingston, RI, United States, 2University of New Hampshire, Durham, NH, United States
Biomechanics and Ecology of Feeding in Elasmobranchs
The feeding behavior of sharks and skates is compared to investigate suction and bite mechanisms. Suction flow is generated by rapid expansion of the oropharyngeal cavities to pull prey into the mouth. In contrast, bite feeders simply grasp the prey between the jaws. Three species are compared: bamboo sharks are specialized suction feeders; little skates are specialized for grasping; and spiny dogfish are generalist suction and bite feeders. The movement of oropharyngeal structures and pressure in the buccal, hyoid and pharyngeal regions were quantified using sonomicrometry and transducers. Regressions and ANOVA’s were used to test the relationship between kinematics and pressure. Bamboo sharks, which have the smallest change in gape area and a large change in hyoid area, generate the greatest oropharyngeal pressures at fast rates of change in hyoid area. Little skates have the largest change in gape area and smallest change in hyoid expansion and consequently generate the weakest pressure with the slowest rate of change in hyoid expansion. Dogfish have an intermediate change in gape area and a large change in hyoid area, but generates intermediate pressure at fast rates of hyoid expansion. Bamboo sharks are benthic ambush predators that take prey from complex reef environments where strong suction is an advantage. Skates are also benthic ambush predators that grab prey after trapping it against the substrate with the fins; therefore rapid jaw movements and suction are not crucial. Dogfish use ram to overtake benthic and pelagic prey and a combination of suction and biting for capture.
0376 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010; AES GRUBER AWARD
Jayne M. Gardiner1, Jelle Atema3, Robert E. Hueter2, Philip J. Motta1
1University of South Florida, Tampa, FL, United States, 2Mote Marine Laboratory, Sarasota, FL, United States, 3Boston University Marine Program, Boston, MA, United States
Multisensory Integration in Shark Feeding Behavior
Feeding by predators involves tracking, precisely localizing and finally striking at and capturing prey. In complex environments, animals rely on multiple senses for such difficult behavioral tasks. Olfaction, vision, mechanoreception, and electroreception have individually been shown to be involved in feeding, but how sharks are integrating the information from these senses to search for food is poorly understood. We are investigating three species from different ecological niches: benthic, suction-feeding nurse sharks hunt nocturnally for fish on reefs; ram-suction feeding bonnetheads scoop crustaceans off the bottom of seagrass beds; and ram-biting blacktip sharks rapidly chase down midwater piscivorous prey. We deprived animals of information from each of the senses, alone and in combination, to elucidate their complementary and alternating roles in feeding on live prey, and to determine how pre-strike information influences capture kinematics. Feeding behavior in intact animals of all three species begins with olfactory tracking, which bonnetheads and nurse sharks use until they are very close to the source, while blacktip sharks demonstrate sensory switching at a distance from the prey, focusing on visual cues to strike. Blacktip sharks can, however, use other sensory cues to locate and capture prey if vision is blocked. With the nares blocked, bonnetheads and blacktip sharks cruise the tank until the prey is in visual range, then strike from a distance, but nurse sharks cease to feed. They can orient to prey using other cues if they happen upon it, but they will not ingest it, suggesting that they require olfaction to feed.
0127 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010; AES GRUBER AWARD
Jeremy Vaudo, Michael Heithaus
Florida International University, North Miami, FL, United States
The Effects of Sampling Unit and Sample Size on Stable Isotopic Community Metrics in a Batoid Community
Stable isotopic analysis is becoming an increasingly popular technique in elasmobranch ecology, but sample sizes of these large predators are often low. Using data from a nearshore batoid community, we examined the effects of using individuals as the sampling unit and sample size on a variety of community isotope metrics. The ranges of d15N and d13C for the batoid community increased substantially when calculated using individuals as opposed to species means (2.7x and 1.9x, respectively). In addition, total niche area for the community was 6.2x larger when calculated using individuals. Sample size had little effect on the estimates of mean d15N and d13C values. Estimates of d15N and d13C range and total niche area, however, initially increased dramatically with sample size before approaching an asymptote. These results suggest small sample sizes and examining communities using mean d15N and d13C values for species may greatly underestimate the niche space occupied and trophic complexity of elasmobranch communities. We recommend the use of individuals as the sampling unit and rarefaction curves to determine if individual species have been adequately sampled for the stable isotopic analysis of elasmobranch communities.
0163 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010; AES GRUBER AWARD
David Shiffman1, Gorka Sancho1, Bryan Frazier2, John Kucklick3, Dan Abel4, Tracey Sutton5, Kristene Parsons5
1College of Charleston Graduate Program in Marine Biology, Charleston, SC, United States, 2South Carolina Department of Natural Resources, Charleston, SC, United States, 3Hollings Marine Laboratory, Charleston, SC, United States, 4Coastal Carolina University, Conway, SC, United States, 5Virginia Institute of Marine Science, Gloucester Point, VA, United States
Stable Isotope Analysis of the Sandbar Shark, Carcharinus plumbeus: A Minimally Invasive Method for Comparison of Diet and Trophic Relationships between Genders, Locations, and Age Classes
The 2006 National Marine Fisheries Service SEDAR for large coastal sharks recommended the gathering of additional diet and trophic relationship data for the sandbar shark, Carcharinus plumbeus. No diet studies of any kind have been performed on South Carolina subpopulations of C. plumbeus, and stable isotope analysis has never been performed on this species. Muscle samples were taken from C. plumbeus caught by the South Carolina Department of Natural Resources and the Virginia Institute of Marine Science shark surveys. The analysis of δ13C and δ 15N from this muscle tissue is ongoing and will be compared with prey species and between other C. plumbeus samples to determine the diet and trophic level of South Carolina and Virginia subpopulations. Intra-subpopulation comparisons will be made to detect potential differences in diet and trophic level between sharks of different age classes and genders.
0138 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
David Ebert1, Joseph Bizzarro1, Marie Cachera1
1Moss Landing Marine Labs, Moss Landing, CA, United States, 2Uuniversity of Washington, Seattle, WA, United States, 3European Institute for Marine Studies, Brest, France
Diet and Trophic Ecology of the Starry Skate (Raja stellulata, Jordan and Gilbert, 1880) off Central California
The diet and trophic ecology of Raja stellulata were investigated off central California using stomach content and stable isotope analysis. Among 137 collected stomach samples, 128 contained prey items (93.4 %). The most important general prey categories for this species were crustaceans (Index of Relative Importance (IRI): 53.2%), teleosts (IRI : 31.9%), and cephalopods (IRI : 15.0%). Among these categories, the following taxa contributed most to dietary composition: hippolytid shrimps, crangonid shrimps, Sebastes spp., agonids, Octopus rubescens, and Rossia pacifica. The trophic level estimated for R. stellulata based on stomach content data was the highest among California skates (3.95). Stable isotopes analysis, conducted using tissue samples from 36 skates and several representative prey items, generally supported results of stomach content analysis. However, trophic level estimates calculated from stomach content analysis were significantly greater than those calculated by stable isotope analysis for paired samples (t = 3.67, P < 0.001). The results of this study indicate that R. stellulata is an upper trophic level predator and a likely competitor of local groundfishes.
0184 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Marcus Drymon, Sean Powers
Dauphin Island Sea Lab, Dauphin Island, AL, United States
Where Old Meets New: Using Gut Contents and Stable Isotopes to Describe the Trophic Ecology of the Consummate Mesopredator, the Atlantic Sharpnose Shark (Rhizopriondon terraenovae)
As proposed regulators of marine foodwebs, it is imperative to quantify the trophic role of sharks in coastal ecosystems. This is particularly true for wide-ranging species, such as the Atlantic sharpnose shark. Two years of monthly longline sampling in the coastal waters of Mississippi and Alabama revealed a regional gradient in the distribution of this species. The aims of this study were to use stable isotopes and gut contents to determine if the observed distributional gradient translated into regional and seasonal variation in trophic role for this species. Across regions, our data indicated that Atlantic sharpnose sharks occupy a trophic position intermediate to secondary and tertiary consumers. Stable isotope values in liver tissue varied significantly between size classes, with adult tissues enriched in nitrogen and depleted in carbon. There was a significant interaction effect between season and region for both nitrogen and carbon, in both liver and muscle tissue. Eastern region nitrogen isotope trends were characterized by high levels in the spring and low levels in the fall. In the western region, carbon signatures were lowest in the spring and fall and highest in the summer. Our stable isotope analysis was supported by examination of stomach contents and highlighted the usefulness of using these two methods in tandem. Our data suggest isotopic results from liver tissue should be interpreted with caution in light of high lipid content in that tissue, and highlight the need to choose appropriate spatial scales when examining the feeding ecology of highly mobile marine predators.
0135 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Simon C. Brown1, Joseph J. Bizzarro2, Gregor M. Cailliet1, David A. Ebert1
1Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, United States, 2School of Aquatic & Fishery Sciences, University of Washington, Seattle, WA, United States
Inter-annual and Regional Variation in the Diet of Two Common Skate Species (Bathyraja aleutica and B. interrupta) on the Western Gulf of Alaska Continental Shelf
The Aleutian (Bathyraja aleutica), and Bering (B. interrupta) skates are common ground fishes occurring throughout the outer continental shelf and upper slope of the Gulf of Alaska. Inter-annual and regional variation in the diet of these skates was investigated to elucidate their ecological roles in the Gulf of Alaska continental shelf ecosystem. Specimens were collected from fishery-independent trawl surveys of the Alaska Department of Fish and Game and National Marine Fisheries Service conducted in three eco-regions: Shelikof Strait, Alaska Peninsula, and the south-eastern side of Kodiak Island during May-September, 2006-2007. Decapod crustaceans were the primary prey items in the diets of both skates. Among decapods, pandalid shrimps dominated the diets of both species. Inter-annual dietary differences were noted for B. aleutica and B. interrupta within Shelikof Strait in that euphausiids comprised a much greater proportion of the diet during 2007, and the contribution of pandalid shrimps was relatively less substantial. The diets of B. aleutica, and B. interrupta during 2006 were similar, consisting primarily of pandalid shrimps, with crabs and fishes of secondary importance. These skates appear to be generalists, consuming locally-abundant invertebrates and fishes (e.g. pandalid shrimps, tanner crabs, gadids, and osmerids). As common benthic competitors with other ground fishes, these two skate species may play an influential role in trophic dynamics and regulation of demersal marine assemblages in the Gulf of Alaska ecosystem.
0621 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Kathleen Duffy1, Nancy Kohler1, W. David McElroy2
1Apex Predators Program, National Marine Fisheries Service, Northeast Fisheries Science Center, Narragansett, RI, United States, 2Population Biology Branch, National Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA, United States
Temporal Changes in the Diets of the Blue Shark Prionace glauca, and Shortfin Mako, Isurus oxyrinchus, in Waters off the Northeastern United States
Using the food habits data collected by the NEFSC Apex Predators Program over the past 38 years, we examined temporal changes in prey species, taxonomic and ecological prey groups, and overall trophic levels for two pelagic shark species, the blue shark, Prionace glauca, and the shortfin mako, Isurus oxyrinchus, found off the northeast coast of the United States. Indices of standardized diet composition were analyzed to identify changes in the prey species consumed, and then related to temporal changes in the distribution and abundance of these prey items. The two shark species have dissimilar feeding strategies and respond differently to environmental changes and fluctuations in prey availability. The blue shark has a generalized diet consisting of teleosts, elasmobranchs, marine mammals, cephalopods, and other food items (e.g., salps, crustaceans, trash) and easily switches between prey types. The shortfin mako is more specialized, consuming mainly bluefish, and appears resistant to dietary change when its preferred prey becomes less abundant.
0451 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Steven Newman1, Richard Handy1, Samuel Gruber2
1University of Plymouth, Plymouth, United Kingdom, 2University of Miami, Florida, United States
Inter-annual Variation in Lemon Shark Feeding Ecology at Bimini Bahamas
Stomach contents of juvenile, nursery bound lemon sharks, Negaprion brevirostris, were sampled concurrently with prey communities over three consecutive years in a highly enclosed nursery (North Sound) with limited to low immigration and emigration rates. Stomach contents were collected from 240 of 432 lemon sharks captured (56 %), and diet described from 420 items. Yellowfin mojarra, Gerres cinereus, were the main prey, although they were less important in the diet of lemon sharks in 2001 (58 %IRI – Index of Relative Importance, 69 %IRI 2000, 78 %IRI 2002). This reflected lower abundance and biomass of mojarra in the environment. Dietary composition differed significantly with year (Chi2 P < 0.05, using pooled categories) with variability due to an increase in the consumption of a wider range of prey in 2001. In 2001 lemon sharks also exhibited increased diet breadth and reduced dietary overlap with other years, and consumed on average smaller teleost prey although this was not significant (Kruskal-Wallis P = 0.07). Prey preference estimates using residual Chi-square and %IRI revealed lemon sharks predominantly fed opportunistically, with some species-specific preferences. Inter- annual variation in lemon shark dietary composition in the North Sound appears to reflect prey communities. Therefore, recent development near this nursery may pose a threat, with anthropogenic impacts on fish communities likely to affect lemon shark diet, and ultimately growth and survival.
0157 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Jason S. Link, Robert J. Gamble, William J. Overholtz, Michael J. Fogarty, Katherine Sosebee
NOAA NMFS NEFSC, Woods Hole, MA, United States
What Would the Ocean Look Like without any Dogfish? Multimodel Inference from Simulations of the Northeast U.S. Large Marine Ecosystem
Spiny dogfish are one of the more ecologically important fish species in the NEUS LME. As such, much speculation exists regarding the hypotheses that dogfish notably compete with or eat other species of commercial importance. Central to much of this speculation is that spiny dogfish are keeping other commercially important stocks at depressed levels, and for those other stocks of interest to recover, dogfish will need to be largely reduced in abundance, if not functionally removed from the ecosystem. To explore the range of possibilities associated with and implied by this set of speculations, we ran several simulations using a range of models. The results from our multimodel simulations generally concurred: after removing or reducing dogfish from the models, most groundfish stocks did not show the anticipated drastic increases. Key prey of dogfish, including small pelagic fishes and squids, varied in their response. Only one major prey of dogfish, ctenophores consistently tended to show a clear, positive response suspected to be due to a release from predation pressure. Collectively our multimodel inference demonstrates the need to consider indirect responses due to the highly interconnected food web of the NEUS LME and that a binary predator-prey response is unlikely in such an ecosystem. We conclude that the potential for unintended consequences remains quite high from such virtual experiments as in these simulations. We thus recommend that scenarios such as these be considered in silico as part of a management strategy evaluation before ever being considered for further application in situ.
0035 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Dana Bethea1, Loraine Hale1, Lisa Hollensead2
1NOAA Fisheries SEFSC Panama City Laboratory, Panama City, FL, United States, 2Florida State University, Tallahassee, FL, United States
Diet of the Roundel Skate Raja texana from the Northern Gulf of Mexico, USA
To better evaluate the trophic role of skates in benthic marine ecosystems, feeding ecology of the roundel skate (Raja texana) was examined from offshore waters in the northern Gulf of Mexico. A complete diet analysis was performed using several single and compound measures of prey quantity. Then, prey items were grouped into six broad prey categories, overall trophic level estimated (TL=3.6), and diet assessed for life- stage (immature and adult), sex, and season (winter, spring, summer, fall). Analysis of 195 non-empty stomachs from immature skates (mean length = 38.4 cm) indicated shrimp were the most important prey category, with Sicyonia sp. and Solenocera sp. the most important identifiable types present. Euphausiids and teleosts were also important prey categories in the diet of immature skates with Bregmaceros spp. was the most important identifiable teleost species present. Adult skate diet (mean length = 50.8) was also predominantly shrimp (n=167 non-empty stomachs); however, fishes, crabs (mostly Portunus sp.), and other unidentifiable crustaceans made up a much larger portion of the diet by prey category. Adults tended to feed on larger prey and had a more diverse diet (H’=4.51) than immature skates (H’=3.11). Diet did not differ significantly between sexes. While shrimp dominated the diet in all seasons, diet was the most diverse in summer (June-August; H’=4.17) and least diverse in fall (September-November; H’=2.84). These are the first quantitative feeding ecology results published for this species; however, it occupies a trophic niche similar to that of several other demersal shark and skate families.
0654 AES Feeding Symposium I, 552 AB, Saturday 10 July 2010
Matthew Ajemian1, Sean Powers1
1University of South Alabama / Dauphin Island Sea Lab, Dauphin Island, AL, United States, 2Dauphin Island Sea Lab, Dauphin Island, AL, United States
Feeding Ecology of Cownose Rays (Rhinoptera bonasus) from the Northern Gulf of Mexico: Further Evidence of Opportunism?
Increases in the abundance of myliobatid rays may pose problems for fisheries management due to their consumption of exploitable shellfish species. The cownose ray (Rhinoptera bonasus) is a myliobatid ray common to the northern Gulf of Mexico (NGOM) known to reach shoal densities of tens of thousands of individuals. Despite their abundance, there are no published studies on the diet of R. bonasus from this region, and thus their impact to shellfisheries is currently unknown. To assess the impact of cownose rays to the NGOM, we collected gut contents from 182 individuals inhabiting Mississippi Sound, Mobile Bay, and Perdido Bay between 2007 and 2009. Prey items were analyzed for frequency of occurrence and percent composition by weight. These data were then used to develop an index of importance (IOI) for each prey group. Our data indicate minimal impact of cownose rays on exploitable shellfish species of the NGOM. Furthermore, cownose rays exhibited significant spatial and ontogenetic variability in diet; adult diets were dominated by crustaceans and echinoderms along barrier islands while juveniles and young-of-the-year (YOY) individuals almost exclusively consumed bivalves in estuarine and riverine areas. Thus, dietary differences among maturity stages were explained by differential habitat partitioning. Overall, cownose ray diet appears to reflect the benthic prey in greatest density at each locale. These findings support previous evidence of cownose ray opportunistic foraging behavior in other regions of the Atlantic.
0523 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Bradley Wetherbee1, Joseph Marini1, Kevin Fung1, Mahmood Shivji2, Richard Nemeth3, Jeremiah Blondeau3, Elizabeth Kadison3
1University of Rhode Island, Kingston, Rhode Island, United States, 2Nova Southeastern University, Fort Lauderdale, Florida, United States, 3University of the Virgin Islands, St. Croix & St. Thomas, Virgin Islands, U.S.
Interactions Among Three Species of Sharks and Grouper Spawning Aggregations in the US Virgin Islands
Grouper spawning aggregations along deep reefs of the US Virgin Islands represent a large potential prey source for large predators including sharks. To examine the relationship between grouper spawning aggregations and sharks, we tagged three species of sharks with acoustic transmitters and monitored their movements over several years using an array of receivers deployed at spawning sites and at locations spanning a stretch of deep reef approximately 100 km in length between the US Virgin Islands and Puerto Rico. Each species of shark demonstrated different behavioral patterns, with temporal and spatial patterns of movement of one species closely associated with spawning events, but little connection between spawning aggregations and behavior of the other two species of sharks. Lemon sharks (Negaprion brevirostris) were present at the spawning sites at a much higher frequency during the spawning season, but largely absent during non-spawning months. Caribbean reef sharks (Carcharhinus perezi) moved little throughout the year and were detected on receivers in proximity to spawning sites almost continuously. Tiger sharks (Galeocerdo cuvier) were detected on receivers throughout the year along the entire extent of the array of receivers and showed no obvious movement patterns associated with spawning activities and little consistency among individuals. Our findings illustrate variable interactions that may occur between different species of sharks and grouper spawning aggregations and that prey availability may influence the spatial and temporal patterns of activity of co-occurring species of sharks in different ways.
0410 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Gregg Poulakis, Philip Stevens, Amy Timmers
Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, Charlotte Harbor Field Laboratory, Port Charlotte, FL, United States
Distribution and Habitat Use of Juvenile Smalltooth Sawfish, Pristis pectinata, in the Charlotte Harbor Estuarine System, Florida
Although endangered smalltooth sawfish (Pristis pectinata) are known to use estuaries during their first 2-3 years, little is known about their life history and ecology while in their juvenile habitat. The purpose of this project was to monitor sawfish in the Charlotte Harbor estuarine system to characterize sawfish seasonality, recruitment, habitat use, and health. During the five year study, we captured sawfish in 1.4% of our random 183-m haul seines and in 14.6% of samples that were non-randomly set. Sawfish stretched total lengths ranged from 671 to 2,172 mm (n = 137; mean = 1,248 mm). Sawfish were captured in all months; most commonly between February and September. Captures of neonates with rostral sheaths allowed estimation of the size range at birth (690-807 mm) and confirms the protracted timing of parturition (November-July) inferred from length frequency data. Although extensive sampling occurred throughout the estuarine system, most sawfish were captured near the mouths of the three major rivers. Five specific locations (‘hotspots’) were identified as having higher catch rates. Logistic regression models identified various combinations of water depth, water temperature, dissolved oxygen, and salinity as influencing the probability of catching a sawfish. Electivity analysis showed that sawfish had an affinity for water < 1 m deep, water > 30°C, moderate to high dissolved oxygen levels (> 6 mg l-1), and salinities between 18 and 30 psu. Higher catch rates of larger sawfish (> 1 yr old) were associated with shoreline habitats with overhanging vegetation (e.g., red mangroves).
0411 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Gregg Poulakis, Philip Stevens, Amy Timmers, Christopher Stafford
Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, Charlotte Harbor Field Laboratory, Port Charlotte, FL, United States
Movements of Juvenile Smalltooth Sawfish, Pristis pectinata, in the Charlotte Harbor Estuarine System, Florida
The movements of endangered juvenile (< 3 yr old) smalltooth sawfish (Pristis pectinata) were monitored during a drought between September 2007 and December 2009 using 33 acoustic listening stations in the tidal Caloosahatchee River, Florida. Movements of 23 sawfish were monitored along the main stem of the river and in 13 backwater habitats (natural mangrove-lined creeks, semi-natural creeks, seawall-lined canals). The daily activity space was 0.7 km, which is similar to other demersal ray species. There was no evidence that sawfish left the river and returned; they remained in the river under a wide range of environmental conditions. Three-fourths (74%) of the sawfish used backwater habitats. Generalized additive models and linear regression found that the distribution of sawfish was significantly related to 90-day lagged salinity; sawfish moved upriver with increasing salinity. When regressed separately for two size classes, the linear relationship between mean river position and salinity was stronger for < 1 yr old sawfish (60 day lag) than for larger sawfish (120 day lag). The lags apparent in the regressions could have occurred for at least three reasons: juvenile sawfish (1) may be more tolerant of changes in salinity than other elasmobranchs; (2) may have strong affinities for specific sites or areas of the river and remain there until conditions change enough for them to respond by relocating; (3) respond to indirect effects of salinity, such as the redistribution of prey populations that are known to exhibit similar distribution responses to lagged environmental changes.
0079 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Michelle Heupel1, Colin Simpfendorfer2, Danielle Knip2, Andrew Chin2, Jimmy White2
1School of Earth and Environmental Sciences, James Cook University, Townsville, Qld, Australia, 2Fishing and Fisheries Research Centre, School of Earth and Environmental Sciences, James Cook University, Townsville, Qld, Australia
Spatial Ecology of Nearshore Elasmobranchs
Nearshore systems are commonly inhabited by a suite of elasmobranch species. Despite extensive data on the distribution and composition of coastal elasmobranchs, limited attention has been given to examining how these species share habitat. This study examines the spatial utilisation of a coastal system by six elasmobranch species. Acoustic telemetry was used to monitor the presence and movements of pigeye, spottail, blacktip reef and scalloped hammerhead sharks in addition to giant shovelnose rays and whitespot guitarfish. Analysis of home range size, overlap of space use within the site and distribution of individuals and populations are examined to define relationships among these species. Preliminary analyses reveal that smaller shark species (pigeye, spottail, blacktip reef) have little overlap in spatial use and distribution. Giant shovelnose rays and whitespot guitarfish overlap in spatial use, but individuals of these species tend not to use the same regions and appear to show some segregation. Scalloped hammerheads showed the broadest movement of any species using the entire monitored region overlapping spatial use with all other species. With an elasmobranch community comprised of over 20 species, studies in Cleveland Bay, Qld reveal that inter-specific interactions occur and that at least some species appear to partition themselves within this habitat.
0608 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
James Ketchum1, Alex Hearn2, Peter Klimley1, Eduardo Espinoza3
1University of California, Davis, Davis, CA, United States, 2Charles Darwin Foundation, Galapagos, Ecuador, 3Galapagos National Park, Galapagos, Ecuador
Diel and Seasonal Movements of Scalloped Hammerhead Sharks (Sphyrna lewini) in the Galapagos Marine Reserve
Sharks are present in great numbers at the Galapagos Marine Reserve (GMR), but little is known about their distribution, abundance and ecology, and illegal fishing is apparently causing their decline. We analyze movements of scalloped hammerheads in the GMR using ultrasonic receivers, examine diel and seasonal dynamics, and evaluate environmental factors. Eighteen scalloped hammerhead sharks were tagged with V16 coded pingers in July 2006 and detected at monitors in Darwin and Wolf (northern archipelago), but not at Gordon Rocks (central archipelago), between July 2006 and July 2007. Detections were more frequent during the day (p<0.001) and a seasonal void occurred between March and May. The majority of sharks (60%) moved between Wolf and Darwin, and few displayed constant residency at a single island, but no significant differences in residency were found between islands (p>0.05). The effect of current velocity on size of sharks at Darwin was noteworthy (p<0.05), where hammerheads were larger there than at Wolf (p<0.05). Based on log-survivorship functions movements were: 1) around island (absence <18 hrs), 2) short-term excursions (absence >18 hrs), 3) mid-term excursions (absence 5-11 days, Wolf; 10-20 days, Darwin), and 4) long-term excursions (absence 20-60 days, Darwin). Connectivity of sharks between islands with no preference of residence means that a large area encompassing both islands functions as prime habitat for hammerheads. Wolf may be the center of short foraging excursions and Darwin a ‘stepping stone’ for long-distance migration for larger hammerheads. This work constitutes baseline information for shark conservation in the GMR.
0332 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Mario Espinoza, Thomas Farrugia, Christopher Lowe
California State University, Long Beach, Long Beach, CA, United States
Influence of Water Temperature on Site Fidelity, Movements and Habitat Use of Gray Smooth-Hound Sharks, Mustelus californicus Gill (1863), in a Newly Restored Estuarine Habitat
It is thought that some elasmobranchs seeking a seasonally warmer environment use shallow temperate embayments as thermal refuges during summer months. Documenting abundances and long-term behavioral patterns in response to thermal gradients could increase our understanding on how the gray smooth-hound shark (GSH) may use a newly restored habitat in southern California. Abundance surveys and acoustic telemetry were employed to examine the influence of water temperature on site fidelity and habitat use of GSH in the new Full Tidal Basin (FTB) of Bolsa Chica. GSH were more abundant during summer months (May-September), and moved out of the basin during the winter (December-February) when this shallow embayment becomes colder faster than coastal waters. Sharks fitted with acoustic transmitters (n=22) were continuously detected inside the FTB for 5-153 d, and only during warmer months. Forays into coastal waters were uncommon until they left for the season. Long-term, fine-scale acoustic data revealed that GSH only used a small core area from the middle FTB (<5%); however, they exhibited consistent diel movement patterns along the basin. From 6-12:00 h, sharks moved towards warmer inner habitats, and from 17-20:00 h they moved to cooler outer habitats. GSH also selected soft mud-bottoms with eelgrass more intensively at night, presumably for feeding on potential prey available in the middle and outer zone. Behavioral data and monthly abundances suggest that this newly restored estuarine habitat may provide a thermal advantage for GSH seeking a seasonally warmer environment.
0698 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Nicholas Whitney1, Harold Pratt2, Theo Pratt2, Jeffrey Carrier1
1Mote Marine Laboratory, Sarasota, FL, United States, 2Mote Center for Tropical Research, Summerland Key, FL, United States, 3Albion College, Albion, MI, United States
It’s 3 A.M., Do You Know What Your Shark is Doing? Fine-scale Ethograms from Accelerometers
Although acoustic and satellite telemetry techniques have greatly enhanced our ability to track shark position and depth, the actual behavior of the animal cannot be determined from broad movement data. We applied three-dimensional acceleration data-loggers to six adult nurse sharks (Ginglymostoma cirratum) in the Florida Keys to provide the first fine-scale ethograms for sharks in the wild. Data-loggers were deployed for periods of 23 to 104 h (59 + 35 h, mean + SD). Four of the six animals were simultaneously tagged with coded acoustic transmitters to acquire the sharks’ location from an array of acoustic receivers, and two sharks carried depth/temperature loggers to provide additional context to acceleration and location data. Behaviors such as swimming, resting, diving, fast-starts, rolling associated with mating, and other behaviors were identifiable and quantified on a per-second basis. Of the two animals with depth loggers, one showed repetitive diving behavior between the surface and 20- 32 m for 33 h after tagging. Accelerometer data showed changes in body posture associated with diving and ascending, and indicated that the shark would occasionally rest on the bottom for several minutes between dives. The animal returned to shallow (< 3 m) water for the final 16 h of the track and mated repeatedly during this time. Thirty- seven of 53 (70%) mating events took place during the day, with only 2 (3.7%) events between the hours of 22:00 and 05:00. No events occurred in water deeper than 4 m, and nearly all were in 2 m or less.
0422 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Aaron Fisk1, Kit Kovacs2, Christian Lydersen2, Peter Klimley3, Warren Joyce4, Steven Campana4
1University of Windsor, Windsor, Ontario, Canada, 2Norwegian Polar Institute, Tromso, Norway, 3University of California Davis, Davis, California, United States, 4Bedford Institute of Oceanography, Dartmounth, Nova Scotia, Canada
Movement Patterns and Dive Depths of Satellite-tagged Greenland Sharks in the North Atlantic and Arctic Ocean
The Greenland shark (Somniosus microcephalus) is among the largest fishes and one of two shark species that inhabits arctic oceans. Although this shark species is thought to be numerous and has a wide distribution, very little is known about its movement patterns or diving behaviour. Pop-up satellite archive tags (SAT, Wildlife Computer) were attached to Greenland sharks captured in the Canadian Arctic (Cumberland Sound, n = 16), European Arctic (Svalbard, n = 20) and eastern seaboard of Canada (Nova Scotia, n = 2) to examine movement patterns, dive depths and temperature preferences, over periods from months to a full year in this little studied elasmobranch. In general, at all locations, Greenland sharks remained at depths ≥ 200 m and at temperatures ≤5o C; several of the sharks spent time at depths greater than 1000 m and made dives to depths of > 1500 m (limit of SAT tag). Although daily locations could not be determined, the pop-off locations for sharks tagged in Cumberland Sound were ~1000 km toward the north east in Baffin Bay. Sharks tagged in Nova Scotia moved 500- 1000 km south along the North American coast or into the mid-Atlantic. There appeared to be no specific pattern to the pop-off locations for sharks tagged in Svalbard. This study demonstrates that the Greenland shark can be found at a wide range of depths (20 – 1500+ m), prefer cold temperatures (5 o C) and can move large distances (> 1000 km) but that behaviour varies considerably among individuals.
0477 AES Behavior & Ecology, 551 AB, Saturday 10 July 2010
Adrian Gleiss1, Brad Norman2, Rory Wilson1
1Swansea University, Swansea, United Kingdom, 2ECOCEAN Inc., Perth, Australia
Being Most Moved by that Sinking Feeling: Implications of Movement Geometry for Optimisation of Travel in Dense Marine Animals
Optimization of animal movement depends on behavioural and ecological context. A primary determinant of movement optimization is travel speed, which modulates both power consumption and distance travelled and thus cost of transport (COT). We investigated the power requirements (using dynamic body acceleration as proxy for power) in relation to movement geometry of nine Whale sharks (Rhincodon typus) and discovered that movement geometry significantly affects power requirements in a manner similar to travel speed. Whale sharks dive repeatedly and use their negative buoyancy to glide during descents, while ascents were characterized by strong locomotory activity. Power requirements of ascents increased with the square of the pitch and were significantly greater than both level and descent swimming. The differences in geometry of different dive types are explored using four semi-empirical optimality models, based on minimum power. These models suggest that some dive types minimise the horizontal cost of transport, whereas others minimise the cost of vertical movement. Negative buoyancy may play a substantial role in the optimisation of both searching and travel. Consideration of speed alone is insufficient to explain optimality in the movement of animals that use changes in potential energy to power part of their locomotory cycle.
0351 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Atsuko Yamaguchi, Shinya Tanaka, Keisuke Furumitsu, Gen Kume
Nagasaki University, Nagasaki, Japan
Feeding Habits of the Fanray Platyrhina sinensis (Batoidea: Platyrhinidae) in Ariake Bay, Japan
Feeding habits of the fanray Platyrhina sinensis were clarified on stomach content analyses of 334 specimens collected in Ariake Bay, Japan from 2003 to 2007. A total of 324 individuals contained food items and 10 (3.0%) were empty. Mean percentage of stomach contents weight per body weight was 0.59.Thirty-seven taxonomic levels of prey items were identified. Based on the percentage of ranking index (%RI), the most important preys were shrimps such as Leptochela gracilis followed by fish and mysids. These three main prey categories collectively had a %RI value of 93.7. There were no differences between sexes in the diet composition, but the ontogenetic dietary shift was observed. Shrimps were consistently the most important prey category throughout the size classes. Meanwhile, smaller individuals actively feed on mysids, and fish constituted the substantial portion of their diet for larger individuals. The Shannon- Wiener diversity index H’ (2.65) indicated that this species is a generalist, and the tendency enhanced in larger individuals.
0168 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Derek Perry1, Greg Skomal1
1University of Massachusetts-Dartmouth School for Marine Science and Technology, New Bedford, MA, United States, 2Massachusetts Division of Marine Fisheries, New Bedford, MA, United States
Feeding Ecology of Smooth Dogfish, Mustelus canis, in Buzzards Bay, Massachusetts
Cape Cod, Massachusetts is generally regarded as a natural barrier to the northern range of smooth dogfish, Mustelus canis, although they have been observed farther north. This study was designed to characterize and quantify the food habits of smooth dogfish in the northern portion if its range where there is significant spatial overlap with relatively high densities of American lobster, Homarus americanus. According to the Lobster Stock Assessment Committee, the natural mortality of lobsters has increased for the Southern New England Stock. Smooth dogfish, coupled with other predators, may have lead to the drastic decline in local abundance of lobster over the last decade in southern New England. Samples were collected from a longline survey and inshore trawl surveys. Analysis of 247 dogfish stomachs found the diet of the smooth dogfish consisted mostly of crustaceans. The most important prey species by percent mass were; Atlantic rock and jonah crabs, Cancer spp (40%), lobster (16%), spider crabs, Libinia spp (14%) and mantis shrimp, Squilla empusa (9%). Analysis suggests that larger smooth dogfish may be a major predator of the American lobster, especially in the fall. Many of the lobsters found in the diet consisted of only claws and legs. These are appendages that the lobster is capable of autotomizing and later regenerating. Non-lethal predation may lessen the smooth dogfish’s potential impact on lobster mortality.
0350 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Maria del Pilar Blanco-Parra1, Felipe Galván-Magaña1, Fernando Márquez- Farías2, Carlos Alberto Niño-Torres4
1Centro Interdisciplinario de Ciencias Marinas, IPN, La Paz, B.C.S., Mexico, 2Instituto Nacional de Pesca. Centro Regional de Investigaciones Pesquera, Mazatlán, Sin., Mexico, 3Universidad Autónoma de Sinaloa. Facultad de Ciencias del Mar, Mazatlán, Sin., Mexico, 4Autónoma de Baja California Sur, Departamento de Biología Marina, La Paz, B.C.S., Mexico
Feeding Ecology of the Banded Guitarfish, Zapteryx exasperata, Inferred from Stable Isotopes and Stomach Contents Analysis
The feeding ecology and trophic level of the banded guitarfish, Zapteryx exasperata, from the Gulf of California were assessed by stable isotope analysis (SIA) of carbon and nitrogen of muscle samples, and by stomach contents analysis (SCA). δ13C and δ15N values showed no significant differences between sexes (ANOVA, F = 0.0 p = 0.94 for δ13C; F = 0.1 p = 0.78 for δ15N), suggesting that males and females have a similar diet. Those similarities were supported by the Morisita-Horn index value (0.75). The main prey species found were the daisy midshipman, Porichthys margaritatus, (54%), followed by the northern anchovy Engraulis mordax (6.84%) and striped cusk eel, Ophidion galeoides (6.35%). No diet overlap between juveniles and adults was found (Cλ= 0.23) and significant isotopic differences were observed (δ13C, ANOVA, F = 13.3 p = 0.0004 and δ15N, ANOVA, F = 4.7 p = 0.03). A general increasing trend in δ15N values with increasing body length (F = 8.15 p = 0.005) was observed. The mean trophic level estimated in this work by the two methods was ~4.1, indicating that this species is a top predator in the Gulf of California. The trophic niche breadth (Bi= 0.11) and diversity index (H’=2.32) indicated that the banded guitarfish from the Gulf of California is a specialist feeder, predating mainly on benthic fishes.
0017 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Mauro Belleggia1, Daniel Figueroa3, Felisa Sánchez1, Claudia Bremec1
1Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Buenos Aires., Argentina, 2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina, 3Laboratorio de Ictiología, FCEyN, Universidad Nacional de Mar del Plata (UNMdP), Mar del Plata, Buenos Aires., Argentina
The Feeding Ecology of Mustelus schmitti in the Southwestern Atlantic: Dietary Shifts and Geographic Variations
Mustelus schmitti is distributed from Brazil (22°S) to Argentina (47o45 ́S) and occurs from shallow waters to 120m. Food habits of M. schmitti were studied based on analysis of stomach contents. Specimens were collected from three research cruises carried out by (INIDEP) during 2008-2009 at four different regions on the Argentinean continental shelf (34oS – 43oS). Prey items were identified to the lowest possible taxon, counted and weighted. The hypothesis that the consumption of each prey group is determined by total length was assessed by fitting generalized linear models (GLM), and using the Maximum Likelihood Estimation to fit a model to data by maximizing an explicit likelihood function. 97.5% of 525 stomachs analyzed contained food. The %IRI revealed that the species fed mostly on decapods (54.7%), followed by polychaetes (24%) and fishes (15.9%). Regional differences were observed among the prey species. M. schmitti showed plasticity in its feeding behavior, factor that contributes to the extensive latitudinal and bathymetrical range exhibited by this species. Models show that polychaetes decreased and fish increased in importance as the narrownose smoothhound grew in size; while crustaceans increased in importance from small to medium size, and then decreased in the large specimens. The feeding on different preys at different stages of the species life cycle suggests an efficient resource partitioning in the study area. Dietary shifts, in general, minimize intraspecific competition and could also favor the wide distribution of this species.
0200 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Antonella Preti, Candan Soykan, Heidi Dewar, Suzanne Kohin
NOAA Fisheries, Southwest Fisheries Science Center, La Jolla, CA, United States
Comparative Feeding Ecology of Shortfin Mako, Blue and Common Thresher Sharks in the California Current, 2002-2008
This study describes the feeding ecology of three pelagic shark species in the California Current. Contents of shortfin mako (Isurus oxyrinchus), blue (Prionace glauca) and common thresher (Alopias vulpinus) shark stomachs sampled from 2002-2008 were identified to the lowest taxonomic level and analyzed using univariate (Geometric Index of Importance [GII], Shannon and Simpson diversity, Sorensen, and Morisita-Horn overlap indices) and multivariate (regression trees, cluster, and discriminant analysis) methods. Stomachs of 330 mako sharks ranging from 53 to 248 cm fork length (FL) were examined; 238 contained 43 prey taxa. Jumbo squid (Dosidicus gigas, GII=46.0) and Pacific saury (Cololabis saira, GII=25.5) were the most important prey. Stomachs of 158 blue sharks ranging from 76 to 248 cm FL were examined; 114 contained 38 prey taxa. Jumbo (GII=33.9) and Gonatus spp. squids (GII=33.6) were the most important prey. Of 225 thresher sharks sampled, ranging from 108 to 228 cm FL, 157 stomachs contained 18 prey taxa. Northern anchovy (Engraulis mordax, GII=68.4) and Pacific sardine (Sardinops sagax, GII=48.5) were the most important prey. Blue and mako shark diets were most similar, while dietary overlap was lowest between blue and thresher sharks. Inter- annual variation in diet was greatest for blue sharks. Overall, mako sharks have the most diverse diet feeding on a range of teleosts and cephalopods; blue sharks generally prefer cephalopods; threshers are more specialized feeding primarily on coastal pelagic teleosts. Despite similarities in life history characteristics and spatial and temporal overlap, diets of the three species are distinct.
0682 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Joseph J. Bizzarro1, Mason N. Dean2, Adam P. Summers3
1University of Washington, School of Aquatic and Fishery Sciences, Seattle, WA, United States, 2Max Planck Institute of Colloids & Interfaces, Potsdam, Germany, 3University of Washington, Friday Harbor Labs, Friday Harbor, WA, United States
Standardized Diet Compositions and Trophic Levels of Rays
The rays are a taxonomically diverse, paraphyletic group within the monophyletic Batoidea, encompassing all species that aren’t skates and representing a majority (~355 extant species) of the superorder. Rays occupy a variety of marine habitats, generally replacing skates in shallow, warm-temperate and tropical seas, but also occurring in oceanic and deep sea regions. A wide variety of feeding modes and methods of prey aquisition have been reported, such as planktivory (e.g., Mobulidae), piscivory (e.g., Gymnuridae), durophagy (e.g., Rhinopteridae), excavation (e.g., Dasyatidae), and electroshock (Torpedinidae). In addition, predation and physical disturbance by rays have been demonstrated to regulate abundance and composition of prey resources. The diet and trophic ecology of this diverse and important group of predatory fishes, however, are poorly known. To better understand the ecological role of rays in marine communities, standardized diet compositions and trophic levels were calculated from a review of applicable quantitative studies. Diet composition and trophic level were estimated for all species with sufficient information and evaluated phylogenetically on ordinal, family, genus, and species levels. These results were then compared to those of similar studies conducted on sharks and skates. In addition, morphological and habitat variables were included to further investigate sources of variability in ray diet compositions and trophic levels. Results of this study will help demonstrate the ecological role of rays in marine communities and distinguish data poor taxa that should be priorities for future research.
0425 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Aleksandra Maljkovic, Isabelle Côté
Simon Fraser University, Burnaby, BC, Canada
Trophic Niche Width Collapse in a Reef-Associated Shark: The Double Whammy Effect of Fisheries on Shark Prey Populations
Fishing, as a pervasive agent of change in marine ecosystems, is thought to alter the trophic relationships of species in defined food webs, although evidence supporting this is generally weak. As large-bodied predators at or near to the top of food webs, sharks are likely to incorporate matter from a wide variety of trophic networks, and the isotopic signatures of their tissues may therefore serve as indicators of trophic restructuring over gradients of environmental or anthropogenic change. We used stable isotope analysis of muscle tissue to define the trophic niche widths of Caribbean reef sharks (Carcharhinus perezi) in δ13C-δ15N niche space. Reef sharks, as well as species representing model trophic guilds, were sampled at six sites over a gradient of fishing pressure in the Bahamas. We show that the trophic niche width of reef sharks inhabiting heavily fished sites has collapsed by >70% relative to sharks inhabiting lightly fished reefs. This pattern of change is due not only to the removal of high trophic level fisheries targets, but also to the collapse of the trophic niches of sympatric species in fished systems. Our results corroborate the suggestion that fisheries indirectly impact populations of non-target species, and highlight the need for holistic ecosystem-based management strategies to conserve marine resources.
0029 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Michael Kinney, Colin Simpfendorfer, Andrew Tobin
James Cook University, Townsville, Queensland, Australia
Reassessing a Purported Communal Shark Nursery in Cleveland Bay, Queensland Australia
While the concept of communal shark nursery areas was originally proposed in the literature nearly 20 years ago, relatively little is known about the ecological pressures affecting young sharks that inhabit such areas. This study seeks to reassess some of the assumptions characterizing communal nursery areas by exploring the ecological characteristics of juvenile sharks in Cleveland Bay, Queensland, Australia, which has been described in the literature as a communal nursery. Fisheries-independent sampling was carried out in the bay from January of 2008 to December of 2009. Sampling was stratified by depth and utilized two gear types targeting large and small sharks to explore species’ distribution and spatial usage throughout the bay. Analysis of catch and general dietary data provides the first indication of possible niche separation among sympatric shark species. In addition, the routine capture of large mature sharks in the shallow waters of the bay using baited long lines indicates that these shallow areas may not provide as much refuge from predation for juveniles as previously hypothesized. Results suggest that the spatial and dietary patterns of the several sympatric shark species utilizing Cleveland Bay as a nursery is more complex then previously assumed. The results of this study will help improve our understanding of shark nursery-area ecology and the links between juvenile and adult sections of the population, which will be essential for creating proper conservation and fisheries management strategies for shark populations.
0072 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
Andrés Felipe Navia1, Enric Cortés2, Paola Andrea Mejiía-Falla3
1Fundación Colombiana para la Investigación y Conservación de Tiburones y Rayas, SQUALUS, Cali, Valle del Cauca, Colombia, 2NOAA-NMFS, Panama City, FL, United States, 3Grupo de Investigación en Ecología Animal, Departamento de Biología, Universidad del Valle, Cali, Valle del Cauca, Colombia
Topological Analysis of the Ecological Importance of Elasmobranch Fishes: The Gulf of Tortugas Food Web, Colombian Pacific Ocean, as a Case Study
We built a trophic network based on a matrix of interspecific trophic relationships to assess the role of elasmobranch fishes in shaping community structure of the Gulf of Tortugas in the Colombian Pacific Ocean. We analyzed diet similarities to define trophic components (nodes)-rather than taxonomical groups-in the network. We evaluated the ecological function of species through topological analysis of their structural importance in trophic networks by applying one local and several mesoscale network indices and assessed the role of elasmobranchs in the set of keystone species for system stability using the “key player” problem approach. We found that elasmobranchs do not play an important ecological role in propagating direct or indirect effects through the system owing to the low and intermediate values of the node degree, centrality and topological importance indices. Only one elasmobranch node (Mustelus spp. and Dasyatis spp.) was included in the keystone species complex identified, contributing only 5% of the spread of effects in the network. Results from our study suggest that elasmobranchs at intermediate trophic levels-commonly referred to as “mesopredators”-are not so important in complex coastal ecosystems because their removal does not result in drastic changes in the structure of the trophic network.
0317 AES Feeding Symposium II, 552 AB, Saturday 10 July 2010
David McElroy1, Joe Bizzarro2, Nancy Kohler3
1National Marine Fisheries Service, Woods Hole, MA, United States, 2University of Washington, Seattle, WA, United States, 3National Marine Fisheries Service, Narragansett, RI, United States
A Review of Selected Methods of Studying Food Habits and Trophic Ecology with Particular Reference to Elasmobranchs
Diet and feeding ecology studies are fundamental to our knowledge of inter-specific relationships and patterns of abundance that govern marine ecosystems. Food habits data are also critical for understanding the life-history and habitat requirements of species. This information is particularly valuable for elasmobranchs as they typically feed at high trophic levels and are long-lived. As ecological-based approaches to resource management have gained acceptance; increased focus, new technologies, and different analytic methods have come to bear in feeding studies. We review data collection and analytical topics with a focus on ones that are debated and exhibit inconsistencies in their application. We offer recommendations on issues such as increasing taxonomic resolution and accounting for alterations due to sample preservation, limiting bias related to sampling gear and other factors, and analytical subjects including data transformations, appropriate grouping of data, sample size sufficiency, and scaling for size. Various indices for quantifying the diet, ecological metrics for comparisons, multivariate ordination, and methods of testing significance are compared using example data. Comparisons utilize published studies as well as dietary data sets for species with both narrow and broad foraging patterns. It is suggested that dietary analysis should be made using number, mass, and occurrence data separately; as each metric provides a different type of information, some of which is lost when combined. Overall, data collection and analysis techniques selected in diet studies will often vary depending on the objectives of the authors, but some methods suggested herein can be utilized to create greater consistency among studies.
0518 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Gregory Skomal1, John Mandelman2
1MA Marine Fisheries, Vineyard Haven, MA, United States, 2New England Aquarium, Boston, MA, United States
Investigations into Physiological Stress in Elasmobranchs: A Historical Perspective
Elasmobranchs, like most fishes, are being subjected to an increasingly vast array of chronic and acute anthropogenic stressors. Although the physiological stress response in teleosts has been studied for decades, this research has lagged far behind in elasmobranchs. Of the limited number of studies conducted to date, most have centered on sharks subjected to capture and handling stress. This work has shown that sharks, like teleosts, exhibit primary and secondary responses to stress that are manifested in their blood biochemistry. The former is characterized by immediate and profound increases in circulating catecholamines and corticosteroids, which are thought to mobilize energy reserves and maintain oxygen supply and osmotic balance. Mediated by these primary responses, the secondary effects of stress in elasmobranchs include hyperglycemia, metabolic (e.g. lacticacidosis) and respiratory (hypercapnia) acidoses, and profound disturbance to ionic, osmotic, and fluid volume homeostasis. The nature and magnitude of these secondary responses are species-specific and may be tightly linked to metabolic scope and thermal physiology along with the type and duration of the stressor in question. Initial studies have also shown that the threshold to cope with, and recover from, various stressors, appears to vary interspecifically. Given the diversity of elasmobranchs, additional studies that characterize the nature, magnitude, and consequences of physiological stress over a broad spectrum of stressors are essential for the development of conservation measures. Due to K-selected life history characteristics in this group, additional studies on the sublethal impacts of various stressors on reproduction, immune function, and growth are particularly in need.
0041 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
W. Gary Anderson
University of Manitoba, Winnipeg, Canada
Probing the Depths: What Can the Endocrine Stress Response in Teleost Fishes Tell Us about Stress in Elasmobranch Fishes
There have been numerous review articles published on various aspects of the endocrine stress response in fish. Topics have ranged from discussing the stressor, be it air exposure, contaminants, or temperature to specific endocrine pathways, be they the sympathetic chromaffin axis or the much studied hypothalamic pituitary interrenal axis. Corticotropin releasing hormone, urotensin, cortisol, growth hormone, catecholamines and deoxycorticsterone are just some of the hormones known to be involved in the stress response in fish. In the last decade the advancement of molecular tools has significantly expanded our understanding and now genomic and proteomic tools are commonly used to examine receptor and enzyme expression and activity. Despite these advances the word fish in many of the titles of these review articles is a misnomer. There is one taxon that lags way behind in our understating of the endocrine stress response. The presence of 1a hydroxycorticosterone in elasmoranchs and our apparent inability to synthesise the steroid based on published techniques has significantly hindered the examination of the stress response in elasmobranch fish. A comparison or perhaps more appropriately, lack thereof, of the endocrine stress response between elasmobranchs and other fish taxon will be discussed.
0064 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Cynthia Awruch1, Colin Simpfendorfer1, Ned Pankhurst2
1James Cook University, Townsville, Queensland, Australia, 2Griffith University, Gold Coast, Queensland, Australia
Are Steroid Hormones Useful to Evaluate Stress in Sharks?
Understanding the stress physiology of sharks that are caught and released is recognised as an important criterion for assessment and effective management of sustainable fisheries. Sharks are important components of Australian’s Inshore Finfish Fishery where there is already a high level of release of sharks by recreational fishers. Despite increasing rates of release of sharks there is no information on their fate after release. To assess the post-release mortality, this study examined the responses of whitespotted spurdog Squalus acanthias and the Australian sharpnose Rhizoprionodon taylori to capture stress by angling. Sharks were captured in a hook line, over a period of two hours, eight blood samples were taken from each animal at: 0, 3, 10, 30, 45, 60, 90 and 120 min post-capture. After initial blood sampling, each shark was placed on a hook line, where it remained freely swimming around the boat until the next blood sampling. During capture and release, the condition of these sharks was recorded. Lactate and glucose concentrations were determined. Plasma samples were chromatographed on a Thin Layer Chromatography (TLC) using corticosterone and cortisone as standards. Subsequently, each TLC track was separated into 1 cm fractions and each fraction analysed by radioimmunoassay. Serum levels of circulating steroid hormones in corticosterone units were quantified. Secondly, steroid hormone levels were correlated with lactate and glucose values of the shark during capture and release to determine the degree of variability in the steroid hormones and the relationship being found between the hormones and different levels of stress.
0174 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Cynthia Awruch1, Colin Simpfendorfer1, Sue Jones2
1Fishing and Fisheries Research Centre, James Cook University, Townsville, Queensland, Australia, 2School of Zoology, University of Tasmania, Hobart, Tasmania, Australia
The Physiology of Deepwater Sharks: Can Biochemical Methods be Used to Develop Stress Profiles?
Deepwater sharks are among the most vulnerable of marine species, increasing on the world’s endangered and threatened species lists. Currently, there is no information available on the fate of released or discarded deepwater sharks to help inform managers. Thus there is a need to quantify the level of stress and post-release mortality of these species. During March 2008, blood samples were obtained from four species of deepwater shark species including 60 individuals of deepwater draughtboard shark (Cephaloscyllium albipinnum), 43 individuals of Australian sawtail catshark (Figaro boardmani), 150 individuals of the endangered greeneye spurdog (Squalus chloroculus) and 23 individuals of the critically endangered southern dogfish (Centrophorus zeehaani). Levels of the stress hormone corticosterone were measured by radioimmunoassay (RIA), and lactate concentrations were determined by spectrophotometry. During capture and release, the condition of these sharks was recorded. We determined if measurable levels of corticosterone are present in four species of deepwater sharks including the variability in hormone levels between species and between individuals within a species. Secondly, we correlated corticosterone levels with lactate levels and with ancillary data on condition of the shark during capture and release to determine the degree of variability in this stress hormone and the relationship being found between this hormone and different levels of stress.
0248 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Richard Brinn2, D. Michelle McComb1, Levy Gomes3, Bernardo Baldisserotto4, Lucelle Dantas de Araujo5, Janessa Sampaio de Abreu Ribeiro6, Jaydione Marcon5
1Florida Atlantic University, Boca Raton, Florida, United States, 2Florida International University, Miami, Florida, United States, 3Centro Universitario Vila Velha, Vila Velha, Brazil, 4Universidade Federal de Santa Maria, Santa Maria, Brazil, 5Universidade do Amazonas, Manaus, Brazil, 6Universidade Federal do Mato Grosso, Cuiaba, Brazil
Stress in the Amazonian Ornamental Cururu Stingray Potamotrygon cf. histrix During Transport
In the middle Rio Negro region of the Brazilian Amazon over 60% of the local economy is based on ornamental fish exports which include several freshwater stingray species in the family Potamotrygonidae. The cururu stingray, Potamotrygon cf. histrix, is one of six legal stingray exports and has an annual quota of 6,000 individuals. Stress is high during the first 24 hours of transport due to a combination of poor water quality and handling procedures. The goals of this study were two-fold: 1) to test the efficacy of an antibiotic and probiotic treatment in reducing stress and mortality during transportation of the freshwater stingray 2) and to confirm whether serum corticosterone is a reliable measurement of stress in this species. A total of 76 stingrays were collected and placed into control, probiotic, and antibiotic treatment groups. Several water parameters including pH, temperature, conductivity, and oxygen were sampled throughout experimentation. Serum corticosterone was measured in individuals at baseline (within 3 minutes of capture), during pre-transport (in river pens), and at 3, 12, and 24 hours into transport. No mortality was observed, and baseline corticosterone levels (7.2 ± 0.7 ng/ml) and pre-transport levels (10.1 ± 0.4) were significantly lower than all other treatments including the 24 h antibiotic (124.9 ± 28.5) and 24 h probiotic (153.2 ± 37.4) treatments. Our results indicate that probiotic and antibiotic treatments did not reduce stress and corticosterone levels increase with transport time and are a reliable indicator of stress in the cururu stingray, Potamotrygon cf. histrix.
0328 AES Stress Symposium, 551 AB, Sunday 11 July 2010
Jill Hendon, Eric Hoffmayer
University of Southern Mississippi-Gulf Coast Research Laboratory, Ocean Springs, MS, United States
The Effects of Capture and Handling Stress on Atlantic Sharpnose Sharks, Rhizoprionodon terraenovae: A Comparison of Single and Repeated Stressors
Studies on stress in vertebrates typically use single or repeated capture and handling protocols to initiate a stress response; however, the difference between the physiological effects of these two methods can be significant. This study investigated the effects of single and repeated capture and handling on the secondary stress response of Atlantic sharpnose sharks, Rhizoprionodon terraenovae, from the northern Gulf of Mexico. Male sharks were captured by rod and reel during the summer months of 2001 and 2002. Single sampled sharks (n=33) were reeled in at 0, 15, 30, 45, or 60 minutes after hooking, and were bled via caudal venipuncture. Repeatedly sampled sharks (n=10) were reeled in immediately after hooking to obtain a time 0 (~1.3 min) blood sample, were released while still on the line, and sampled again at 15 minute intervals for 60 minutes. All sharks were measured (total length, cm), weighed (kg), and released after the final blood draw. The secondary stress parameters analyzed were plasma lactate, glucose, osmolality, and hematocrit. Repeatedly sampled sharks exhibited heightened levels, as compared to single sampled sharks, for lactate (p<0.05), osmolality (p<0.05), and glucose (p>0.05) at all times except 0. Maximal concentration differences of 217.5%, 9.8%, and 41.6% occurred at time 60 for lactate, osmolalaity, and glucose levels respectively. Hematocrit levels were consistent for both stress protocols at all time points (p>0.05). These data indicate that the stress protocol and duration affects the physiological response of Atlantic sharpnose sharks and needs to be considered when making comparisons.
0264 AES Stress Symposium I, 551 AB, Sunday 11 July 2010; AES GRUBER AWARD
Angela Cicia1, Lela Schlenker2, James Sulikowski1, John Mandelman2
1University of New England, Biddeford, Maine, United States, 2New England Aquarium, Boston, Massachusetts, United States
The Acute Physiological Effects and Recovery from Graded Periods of Air Exposure in Skates from the Western Gulf of Maine
Sustained bouts of air exposure occur during capture/handling processes, and functionally inhibit ventilation in obligate water-breathing fishes. However, despite reports of widely ranging interspecific abilities to cope with periods of air exposure, few studies have investigated the direct physiological alterations it causes, and no study has addressed this in western North Atlantic Rajids (skates). In the current laboratory study, mixed venous/arterial whole-blood samples and clinical data have been obtained from the little skate (Leucoraja erinacea) (n = 32) immediately following variable bouts of air- exposure, and again 5-days later to evaluate recovery. Although analyses to derive additional ionic and metabolic values and intracellular (erythrocyte) pH are underway, preliminary results show that ventilation rates decreased in each group exposed to air. Blood acid-base status (declines in blood pH and pO2; and HCO3- concentrations; elevations in pCO2) became progressively more disturbed the longer skates were subjected to air. Interestingly, blood lactate concentrations remained negligible even in the most prolonged (50-minute air exposure) group, suggesting L. erinacea did not shift to anaerobiosis during forced hypoventilation. Blood pH declines were likely the primary result of hypercapnia and respiratory acidosis due to the compromised ability to offload CO2 at the gills. After a 5-day recovery period, blood acid-base disturbances were resolved in all experimental groups. However, 28% of skates subjected to 50 minutes of air exposure died before recovery status could be assessed. Data on the nature and threshold for coping with air exposure by species can have considerable influence on regulatory fishing measures.
0188 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Edward Brooks1, Andrew Danylchuk8, Steven Cooke4, John Mandelman6, Greg Skomal7, David Philipp3, Katherine Sloman2, David Sims5, Stephanie Liss3, Cory Suski3
1Cape Eleuthera Institute, Eleuthera, Bahamas, 2University of Plymouth, Plymouth, Devon, United Kingdom, 3University of Illinois, Urbana, Illinois, United States, 4Carlton University, Ottawa, Ontario, Canada, 5Marine Biological Association of the United Kingdom, Plymouth, Devon, United Kingdom, 6New England Aquarium, Central Wharf, Boston, Massachusetts, United States, 7Massachusetts Division of Marine Fisheries, Oak Bluff, Massachusetts, United States, 8University of Massachusetts, Amherst, Massachusetts, United States
The Physiological Consequences of Longline Capture in Caribbean Reef Sharks (Carcharhinus perezi)
Longline fishing is arguably the most common capture method for sharks around the world, resulting in the capture and release of a large number of non-target or protected species annually. To date, however, the physiological disruption caused by longline capture, and the subsequent impacts on post-release survival and behaviour are poorly understood. To quantify the lethal and sub-lethal effects of longline capture in the commonly exploited Caribbean reef shark (Carcharhinus perezi), 40 individuals (Male=18, Female=22) were captured using standard, mid-water longlines. Hook timers provided accurate hooking duration to the nearest minute. Once sharks were landed, to quantify their levels of stress, blood samples were taken and used to measure a suite of physiological parameters. No sharks died while on the longline. Although there were significant non-linear relationships between hooking duration and pH, lactate, pCO2 and glucose, there was no significant variation in HCO3- and haematocrit. Analysis is ongoing for plasma ion concentrations (Na+, Cl-, Ca2+, K+, Mg2+), whole blood haemoglobin, and urea. In parameters analyzed to date, the greatest level of physiological disruption appears to occur at 100-150 minutes of hooking; control animals and those hooked for the maximum duration of 240 minutes presented the least disturbed blood chemistry. Further analysis of the ionic and osmotic disruption induced by the capture event will likely clarify these initial trends and aid in predicting the fate of sharks post-release.
0723 AES Stress Symposium I, 551 AB, Sunday 11 July 2010; AES GRUBER AWARD
Heather Marshall1, Lyndsay Field1, Achankeng Afiadata1, Chugey Sepulveda2, Greg Skomal3, Diego Bernal1
1University of Massachusetts Dartmouth, Dartmouth, MA, United States, 2Pfleger Institute of Environmental Research, Oceanside, CA, United States, 3Massachusetts Division of Marine Fisheries, Martha’s Vineyard, MA, United States
Molecular and Biochemical Stress-response in the Blood of Longline Captured Pelagic Sharks
Assessments of worldwide longline fisheries reveal that sharks constitute a large portion of bycatch for this gear type. A combination of recently enacted fishing regulations along and the low economic value of these catches, results in a large percentage of incidentally captured sharks being released. To date, little information exists on the rates of post-release survival for many shark species, and thus the full impact of longline fisheries on shark populations cannot be fully estimated. Recent studies have addressed the possibility of using biochemical profiles of secondary haematological stress parameters to predict post-release survivorship, yet little is known about interspecific differences in these indicators. This study sought to compare electrolytes (Na+, Cl-, Mg2+, Ca2+, and K+), metabolites (glucose and lactate), hematocrit, and heat shock protein 70 (HSP70) parameters between eight species of longline captured sharks (n = 151). Statistical comparison of parameters was conducted according to species, family, and ecological classification. Data reveal species-specific parameter differences in response to longline capture, as well as differences by family (i.e., Lamnidae versus Carcharhinidae) and ecological (i.e., oceanic versus coastal) classification. Results suggest that differences in locomotive and respiratory adaptations between study species bring about differences in stress-response by these sharks to longline capture. This study is the first to report a haematological secondary stress response assessment for such a large number of pelagic shark species, and lays the groundwork for developing species-specific indices for predicting post-release survivorship of longline caught sharks.
0724 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Diego Bernal1, Craig Heberer2, Scott Aalbers3, Suzzane Kohin2, Bart DiFiore4, Chugey Sepulveda3
1University of Massachusetts Dartmouth, Dartmouth, MA, United States, 2NMFS, Southwest Fisheries Science Center, La Jolla, CA, United States, 3Pfleger Institute of Environmental Research, Oceanside, CA, United States, 4Middelburry College, Middelburry, VT, United States
Molecular and Biochemical Stress Responses and Post-release Survival in Thresher Sharks Captured by the California Recreational Fishery
The common thresher shark (Alopias vulpinus) is target of a growing recreational fishery in southern California utilizing heavy troll gear with large J-hooks. The use of this gear results in a high percentage of sharks being foul-hooked in the caudal fin, which reduces their ability for forward locomotion and ram ventilation, both of which may ultimately impact post-release survivorship. The focus of this study was to: assess the survivorship of rod-and-reel captured and released common thresher sharks, and, to quantify the physiological indicators of stress in the blood associated with these capture techniques. Survivorship estimates were quantified using pop-off satellite archival tags (PSATs) deployed on sharks hooked by the caudal fin using the methods of the recreational shark fishery. A total of 19 PSATs were deployed on threshers (165-221 cm fork length and ~68 to 204 kg) with ~74% of the tagged sharks surviving the capture-event. All observed mortalities were from individuals with fight times that exceed 85 min. Although blood stress parameters from nine threshers experiencing varying fight times show a minimal change in several plasma levels of electrolytes and metabolites (e.g., Na+, Cl-, K+, Ca++, Mg++, and glucose), lactate, hematocrit and blood-associated stress proteins (i.e., heat shock proteins) significantly increased with the capture-related event. This suggests that stress levels increase with fight time and that a prolonged struggle time (> 85 min) associated with this foul-hooking techniques lead to high mortality, which raises questions about catch and release conservation measures for this type of recreational fishery.
0151 AES Stress Symposium I, 551 AB, Sunday 11 July 2010; AES GRUBER AWARD
Lorenz H. Frick1, Richard D. Reina1, Terence I. Walker2
1Monash University, Melbourne, Australia, 2Marine and Freshwater Fisheries Research Institute, Queenscliff, Australia
Are Physiological Indicators of Stress Reliable Predictors for Delayed Mortality of Sharks? Insights from a Controlled Study on Capture Stress
The immediate and delayed effects of capture stress on the physiology of sharks remain understudied, despite the urgent need for effective elasmobranch conservation and management measures. An assessment of the proportion of discarded sharks that die post-release as a consequence of excessive physiological stress requires a reliable physiological indicator of stress that allows predicting of the survival of a discarded shark. We exposed Port Jackson sharks Heterodontus portusjacksoni and gummy sharks Mustelus antarcticus to varying durations of gill-net, longline, and trawl capture in a controlled setting, and monitored their post-capture condition via serial blood sampling during a 72-h recovery period subsequent to the capture event. Port Jackson sharks appear to be highly resilient to capture stress, as evidenced by a low degree of physiological disturbance and no mortality observed during or after any experiments. However, gummy sharks experienced severe disruptions to their acid-base and hydro- mineral balance, which were irreversible in some cases. Sharks that died post-capture showed significantly higher concentrations of plasma lactate and potassium, but these differences did not become apparent until hours after the capture event. These blood variables are therefore not suitable predictors of delayed mortality. Blood pH of gummy sharks was significantly depressed immediately after capture due to a combination of metabolic and respiratory acidosis. Intramuscular lactate concentration was highest immediately after capture, indicating that gummy sharks experienced intracellular acidosis. Suitability of blood and intracellular pH therefore deserves further investigation. These findings will help to elaborate methods for an assessment of post- release mortality of discarded sharks.
0566 AES Stress Symposium I, 551 AB, Sunday 11 July 2010
Lisa Naples1, Natalie Mylniczenko2, Trevor Zachariah3, Forrest Young4
1John G Shedd Aquarium, Chicago, Illinois, United States, 2Disney’s Animal Kingdom, Orlando, Florida, United States, 3Chicago Zoological and Aquatic Animal Residency, Chicago Illinois, United States, 4Dynasty Marine Associates, Marathon, Florida, United States
The Influence of Venipuncture Site on Secondary Blood Physiological Values During Elasmobranch Health and Stress Investigations
It is important when evaluating hematologic parameters and establishing reference values to recognize any differences in regards to the collection site. Following the evaluation and comparison of hematocrit values from two venipuncture sites in captive and wild sharks, the current study was developed. As significant changes in the acid- base balance of elasmobranchs can occur during handling or transportation, blood gas assessment within minutes of collection is essential to provide information regarding immediate physiological stressors. Ths information can be applied to stress assessment and the limitation of morbidity and mortality during capture situations. The current study was developed to 1) evaluate baseline blood gas values of a captive population of elasmobranchs ranging from benthic to pelagic species, 2) to evaluate the use of a portable clinical analyzer boat-side during elasmobranch capture, and 3) to compare two commonly used blood collection sites in an effort to determine differences between the two. Pelagic, intermediate and benthic elasmobranchs at the John G Shedd Aquarium were immobilized for health screens. In addition, wild pelagic elasmobranch species were hook and line caught in the costal waters of Florida several miles within the Keys during normal collecting trips for Dynasty Marine Associates. Wild caught animals were immediately brought boat-side, netted and manually restrained. Blood was obtained from the ventral tail artery and within 30 seconds from the dorsal sinus. Samples were immediately processed with the I-STAT (Heska, Fort Collins, CO 80525) portable clinical analyzer to run standard blood gas panels. Statistical comparisons were made for collection site, gender, and captivity status.
0412 AES Genetics, 552 AB, Sunday 11 July 2010
Jennifer V. Schmidt1, Chien-Chi Chen2, Saad I. Sheikh1, Mark G. Meekan3, Bradley M. Norman4, Shoou-Jeng Joung2
1University of Illinois at Chicago, Chicago, IL, United States, 2National Taiwan Ocean University, Keelung, Taiwan, 3Australian Institute of Marine Sciences, Crawley, WA, Australia, 4Ecocean Inc., Cotttesloe, WA, Australia
Paternity Analysis in a Litter of Whale Shark Embryos
The reproductive biology of the whale shark (Rhincodon typus) is poorly understood on all levels. A 10.6 meter female whale shark caught off the coast of Taiwan in 1995 carried more than 300 embryos in her uteri, ranging in developmental stage from embryos still in egg cases, to hatched, near-term animals. This litter established that whale sharks develop by aplacental yolk-sac viviparity, and the range of developmental stages within the litter indicated ongoing fertilization over an extended period of time. This suggested that embryos of varying ages might have been sired by different males. Recently published microsatellite markers for R. typus have now allowed paternity investigation in a subset of 29 embryos from this female. The embryos available for analysis represent ~10% of the initial litter, and span nearly the full range of size and developmental stage. Genetic analysis determined that all embryos are likely to be full siblings sired by a single male. These data suggest that female whale sharks may be capable of long-term sperm storage after a single mating event, which may be a physiological adaptation to the limited mating opportunities available in a species that segregates by sex and age, and likely exists at low density in the open ocean. No tissue was available from the female for genetic analysis, but a 1222 nucleotide region of the maternally-inherited mitochondrial control region was sequenced from the embryos, identifying a novel haplotype most similar to two haptolypes previously isolated from the western Indian Ocean.
0013 AES Genetics, 552 AB, Sunday 11 July 2010
Toby Daly-Engel1, Kanesa Duncan3, Kim Holland2, John Coffey2, Holly Nance4, Robert Toonen2, Brian Bowen2
1University of Arizona, Tucson, AZ, United States, 2Hawaii Institute of
0563 AES Genetics, 552 AB, Sunday 11 July 2010
Caitlin Curtis1, Mike Tringali1, Gregg Poulakis2
1Florida Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, St Petersburg, FL, United States, 2Florida Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Port Charlotte, FL, United States
Population Genetics of the Endangered Smalltooth Sawfish, Pristis pectinata
The smalltooth sawfish, Pristis pectinata, is thought to have undergone a severe population level decline, and has been included on the United States endangered species list since 2003. In 2009, National Marine Fisheries Service designated over 800,000 acres of critical nursery habitat areas to aid in protecting this species along the southern / southwestern Florida coastline. We are characterizing the genetic diversity in and among these nursery areas, including the Peace and Caloosahatchee River drainages of southwestern Florida. In addition, we are assessing the genetic relatedness among individuals of the same size class (i.e. potential sibling groups) that were tagged and non-lethally sampled at the same time and location. To date, we have analyzed over 100 samples with 16 polymorphic microsatellite loci, and the heterozygosity and allelism among these individuals is surprisingly high, up to 33 alleles for one microsatellite locus. Preliminary analyses show no sign of a recent genetic bottleneck. Genetic relatedness among potential sibling groups within and among river drainages will also be discussed. For example, preliminary data suggest that up to half of the potential sibling groups tagged in the Peace River contain at least a pair of full siblings, though this percentage may be lower in the Caloosahatchee River. In conjunction with tagging and acoustic telemetry studies, these genetic relatedness estimates are being applied to test hypotheses pertaining to habitat usage for young of the year P. pectinata in the Caloosahatchee canal system.
Marine Biology, Kaneohe, HI, United States, 3University of Hawaii, Honolulu, HI, United States, 4Clemson University, Clemson, SC, United States
Male-Mediated Dispersal in an Incipient Global Ring Species, the Scalloped Hammerhead Shark (Sphyrna lewini)
Many sharks have high dispersal ability coupled with coastal habitat requirements, potentially yielding complex population structure with implications for management of depleted stocks. The scalloped hammerhead, Sphyrna lewini, is a large shark with a circumglobal distribution, observed in the open ocean but linked ontogenetically to coastal embayments for parturition and juvenile development. A previous mtDNA survey demonstrated strong genetic partitioning overall (global ФST = 0.519) and significant population separations across oceans and between discontinuous continental coastlines. Here we survey the same global range with increased sample coverage (N = 403) and 13 microsatellite loci to assess the male contribution to dispersal and population structure. Biparentally-inherited microsatellites reveal low or absent genetic structure across ocean basins and global genetic differentiation (FST = 0.035) that is an order of magnitude lower than the corresponding measures for maternal mtDNA lineages (ФST = 0.519). Nuclear allelic richness and heterozygosity are high throughout Indo-Pacific, while genetic structure is low. In contrast, allelic diversity is low while population structure is higher for populations at the ends of the range in the West Atlantic and East Pacific. These data are consistent with the proposed Indo-Pacific center of origin for S. lewini, and indicate that females are philopatric or adhere to coastal habitats, while males facilitate gene flow across oceanic expanses. We conclude that Sphyrna lewini is an incipient global ring species with gene flow between populations countering the isolating effects of distance, whose genetic continuity is impeded only by secondary vicariance at the Isthmus of Panama.
0652 AES Genetics, 552 AB, Sunday 11 July 2010
Demian Chapman1, Kevin Feldheim2, Rowena Eng1, Lisa Natanson3, Mahmood Shivji4
1Stony Brook University, Stony Brook, NY, United States, 2Field Museum of Chicago, Chicago, IL, United States, 3National Marine Fisheries Service, Narragansset, RI, United States, 4Nova Southeastern University, Dania Beach, FL, United States
Is There Genetic Evidence of a Recent Population Bottleneck in White Sharks (Carcharodon carcharias) from the Northwest Atlantic?
The white shark, Carcharodon carcharias, is one of the largest marine predators in the northwest Atlantic, where some authors suggest it has declined precipitously due to overexploitation. This seems plausible, because from the 1970s onward this species was targeted by recreational anglers and featured as bycatch in expanding commercial shark fisheries. White sharks were subsequently fully protected in the northwest Atlantic by the National Marine Fisheries Service (NMFS) in 1997, although illegal harvest and trade is known to occur in this region. A resurgence of interest in the status of the northwest Atlantic white shark population has stemmed from recent high-profile sightings of this charismatic species. We are currently employing a multi-analytical approach to test the hypothesis that northwest Atlantic white sharks have experienced a recent loss of genetic diversity due to a population bottleneck. We show that contemporary northwest Atlantic white sharks are genetically distinct from other populations and comprise a demographically distinct unit (pairwise Φst ranging from 0.125 to 0.88) that has relatively low mtCR diversity (4 haplotyopes in 23 animals). We will present an ongoing analysis of nuclear microsatellite data that aims to determine if these markers register a signal of recent population decline (e.g. M-ratio testing). Lastly, we detail attempts to reconstruct the genetic diversity of white sharks in the 1960s and 1970s using DNA recovered from archived vertebrae. Historical genetic diversity will be directly compared to contemporary genetic diversity in this study, which could serve as a model for similar studies of other elasmobranchs.
0543 AES Stress Symposium II, 551 AB, Sunday 11 July 2010
Michael Hyatt1, Paul Anderson2, Patrick O’Donnell3, Ilze Berzins4
1Georgia Aquarium, Atlanta, GA, United States, 2The Florida Aquarium Center for Conservation, Tampa, FL, United States, 3Rookery Bay National Estuarine Research Reserve, Naples, FL, United States, 4John G. Shedd Aquarium, Chicago, IL, United States
Assessment and Comparison of Acid-Base Derangements from Capture and Handling Methods Among Three Species of Sharks: Carcharhinus leucas, Negaprion brevirostris, and Sphyrna tiburo
Blood gases were evaluated in three species of wild sharks (Sphyrna tiburo, Negaprion brevirostris and Carcharhinus leucas) in response to acute capture and handling stress.
Blood was sampled when first caught from either longline or gillnet, and again prior to release after handling, measuring and tagging. Blood was assayed for pH, partial pressure of carbon dioxide (pCO2), bicarbonate (HCO3), and lactate. Reference limits of the initial blood draw were established for each species, as well as the rate of change in pH (ΔpH/Δt) and lactate (Δlac/Δt) from capture to release. ANOVA and Tukey’s test were employed to detect species differences in these measures. pH in C. leucas (7.11 ± 0.03) (mean ± SE) was significantly lower than in S. tiburo (7.24 ± 0.03); pCO2 in C. leucas (10.40 mmHg ± 0.60) was significantly higher than in N. brevirostris (7.87 mmHg ± 0.64); HCO3 in N. brevirostris (3.30 mmol/L ± 0.31) was significantly lower than in S. tiburo (4.01 mmol/L ± 0.22); and Δlac/Δt in S. tiburo (0.64 mmol/L/min ± 0.06) was significantly higher than in N. brevirostris (0.36 mmol/L/min ± 0.10). C. leucas caught in gillnets suffered a greater degree of acidosis than on longlines, accompanied by a higher lactate and pCO2, suggestive of a mixed metabolic and respiratory acidosis. Discriminant analyses of pH, pCO2 and lactate predicted capture method of C. leucas with high (84.6%) accuracy, but predicted behavioral release condition with less accuracy (64%); only pCO2 was significantly lower in sharks graded with a higher (“good”) condition.
0120 AES Stress Symposium II, 551 AB, Sunday 11 July 2010
Rachel Wilborn1, Wayne A. Bennett1
1Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School for Marine and Atmoshperic Science, University of Miami, Miami, FL, United States, 2University of West Florida, Pensacola, FL, United States
Effects of Exhaustive Exercise on Juvenile and Adult Stingrays, Dasyatis sabina
Physiological responses to exhaustive exercise provide insight into swim performance limits in fish, and potentially highlight ontogenetic differences between adults and juveniles of the same species. Metabolic responses to swim exhaustion (i.e., oxygen consumption, ventilation rates, and blood lactate) were quantified in juvenile and adult Atlantic stingrays (Dasyatis sabina). Adult stingrays were significantly larger and heavier than juveniles (Independent T-test, P<0.01) providing a definitive comparison. A direct correlation between body size and metabolism was found for many parameters measured. Adult stingray oxygen consumption rates were 3-fold greater than juvenile rates pre-exhaustion (0.0339 and 0.0127 mg g-0.67 hr-1 respectively) and 4-fold greater post-exhaustion (0.0391 and 0.0094 mg g-0.67 hr-1 respectively). However, pre- and post exhaustion ventilation rates were not significantly different between life stages. Adult hematological lactic acid values post-exhaustion were 150% greater than juveniles (0.9899 mmol/L and 0.6418 mmol/L). Metabolic adjustments to exhaustive swimming (i.e., escape responses) may impact overall survival strategies as related to predator avoidance tactics, habitat selection, and utilization.
0719 AES Stress Symposium II, 551 AB, Sunday 11 July 2010
Gillian M. C. Renshaw
Hypoxia and Ischemia Research Unit, Griffith University, Queensland, Australia, Australia
Assessing Oxidative Stress in Sharks and Rays
Hypoxia and reoxygenation usually triggers an increase in the formation of reactive oxygen species (ROS) by mitochondria, which is greatest during the reoxygenation phase. While the mismatch between ROS production and antioxidant defence results in oxidative stress, the down stream effects of increased ROS production range from lipid peroxidation to the initiation of cell death. The giant shovel nose ray (Glaucostegus typus) and the epaulette shark (Hemiscyllium ocellatum) can live in habitats characterised by intermittently variable oxygen levels yet their tolerance to hypoxia is markedly different, Hemiscyllium ocellatum can tolerate anoxia while Glaucostegus typus can not. The level of lipid peroxidation and the ratio of oxidised versus reduced glutathione was measured in both species after a single standardised exposure to 5% of normal saturation that represented a maximal challenge.
0471 AES Stress Symposium II, 551 AB, Sunday 11 July 2010
University of North Florida, Jacksonville, FL, United States
Biomarkers of Physiological Stress Caused by Exposure to Environmental Pollutants in Sharks and their Relatives
Due to numerous factors, such as their relatively large size, slow growth and metabolism, and high trophic level, sharks and their relatives have the tendency to accumulate elevated concentrations of environmental pollutants. Because of this, it is critical to develop and use methods for detecting physiological effects of pollutant exposure in elasmobranchs. However, to date, very little research has focused on biomarkers of pollutant stress in these animals. In this review, we discuss recent research efforts focused on developing molecular and protein biomarkers of several environmental pollutants in sharks and rays including heavy metals, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, organophosphate pesticides, and estrogen-mimicking substances. We also highlight new efforts to use cellular biomarkers of pollutant stress in elasmobranchs, such as those that can detect gene and chromosome damage as a result of exposure to genotoxic substances.
0444 AES Stress Symposium II, 551 AB, Sunday 11 July 2010
Brandon Casper, Michele Halvorsen, Arthur Popper
Department of Biology, University of Maryland, College Park, MD, United States
Sharks and Environmental Noise… Are We Stressing Them Out?
Anthropogenic noise has become a major global issue as it is becoming more apparent that human aquatic activities can have a negative effect on the survival of large fish stocks. It is not clear, though, whether these noise issues could have an effect on the health and behavior of elasmobranch fishes, many of which are already being severely threatened worldwide due to overfishing. Many sources of anthropogenic noise produce sounds within the hearing range of these fishes, but it is unknown if elasmobranchs could be affected by these sounds. A review will be made of what is known in regards to elasmobranch hearing as well as a discussion of current noise exposure research involving fishes and other aquatic organisms and how it might be applicable to elasmobranch physiology. With these in mind, the goal will be to address whether anthropogenic noise could be having deleterious effects on elasmobranch fishes.
0050 AES Morphology, 552 AB, Sunday 11 July 2010
Dan Huber1, Danielle Noaker1, Paul Anderson2, Ilze Berzins3
1University of Tampa, Tampa, FL, United States, 2Florida Aquarium Center for Conservation, Tampa, FL, United States, 3J.G. Shedd Aquarium, Chicago, IL, United States
Biomechanics of Spinal Deformities in Captive Sandtiger Sharks Carcharias taurus
The sandtiger shark Carcharias taurus is a popular exhibit specimen in public aquaria. However, captive C. taurus are prone to developing spinal deformities that often result in euthanasia. Biomechanical analyses of sections of vertebral columns and individual vertebrae from healthy and deformed C. taurus were conducted to characterize the mechanical basis of these skeletal deformities. Vertebral sections were subjected to bending tests, while individual vertebrae were subjected to compression tests and mineral content analyses. The flexural stiffness (resistance to bending) of vertebral columns from healthy animals was greater than that of deformed animals due to greater second moment of area, a structural property that measures the distribution of skeletal material away from the central axis of the vertebral column. The force required to buckle the vertebral column was greater in the healthy specimens as well. The compressive stiffness, yield strength, yield strain, and ultimate strength of vertebrae from healthy animals were greater than those from deformed animals. However, the compressive stiffness and ultimate strength of vertebrae from healthy specimens were still lower than those of most species for which data is available, suggesting an inherent predisposition for spinal deformity in captive settings where natural swimming behavior is constrained (increased swim-to-glide ratio, asymmetric swimming). This study is one portion of a collaborative investigation of husbandry practices, animal behavior, nutritional physiology, and spinal biomechanics of C. taurus, with the ultimate intention of developing better husbandry guidelines to improve captive animal health and reduce dependence on wild stocks for exhibit specimens.
0575 AES Morphology, 552 AB, Sunday 11 July 2010
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Hammerhead Sharks (Elasmobranchii: Sphyrnidae) from the Indo-Pacific: More Species Than it Seems?
Among sharks, the Carcharhiniformes comprises more than 55% of all living species. In this order, the family Sphyrnidae, whichincludes all the hammerhead sharks, is characterized by the presence of a laterally expanded head forming the cephalofoil. Between all the 8 living species in this family, Sphyrna lewini is distinguished for its largest occurrence, which is cosmopolitan, and Eusphyra blochii is recognized for being the only endemic species of Sphyrnidae. Both species occurs in the Indo-Pacific ocean, and their internal anatomy were studied especially concerning the head. Differences in the anatmomy of the cephalofoil were found among exemplars of each studied species. I will discuss the preliminary results on the cranial anatomy in these two species, questioning if there are just different subpopulations of S. lewini and E. blochii, based on new cranial characters. This includes to show some peculiar characters between the subpopulations of S. lewini and E. blochi in the Indo-Pacific ocean. The preliminary results on the internal and external morphologies suggests, at least, 3 subpopulations of S. lewini and 2 of E. blochii in the Indo-Pacific.The Indic ocean is showed as a distinguished region to study morphological patterns that were never described in hammerheadsharks, suggesting two possibilities: different subpopulations or more species than was thought.
0286 AES Morphology, 552 AB, Sunday 11 July 2010
Kara Yopak1, Shaara Ainsley2, David Ebert2, Lawrence Frank1
1University of California San Diego, Center for Scientific Computation in Imaging, La Jolla, CA, United States, 2Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA, United States
Skating Over the Issue: Neural Adaptations to the Bathyal Environment in Deep-sea Skates
The deep sea is a vast and still largely unexplored habitat. As neural development in fishes has been shown to reflect morphological adaptations, particularly in extreme environments, quantitative analysis of deep-sea species is potentially highly informative. Members of the family Rajidae (skates) make up a highly diverse group, comprising approximately 40% of all batoids, with 30 genera across approximately 280 species. Despite their diversity, few studies have quantified interspecific brain size (encephalization) or the relative development of major brain areas (telencephalon, diencephalon, mesencephalon, cerebellum, medulla) and discrete sub-sections of these brain structures that receive direct sensory input (e.g. optic tectum and the dorsal and medial octavolateral nuclei) in rajids. The brains of five species of deep-sea skate, Bathyraja aleutica, B. parmifera, Raja binoculata, R. rhina, Rhinoraja interrupta, ranging in primary habitat depth from 50m to as deep as 1,600m, were assessed and compared to the brain organization of other batoids (n=24) as well as a broad dataset of sharks and holocephalans (n=84). Trends show both strong phylogenetic patterns as well as possible ecological adaptations. Though morphologically dissimilar, pilot data suggest similar patterns of brain organization between the deep-sea members of Rajidae and the deep- sea sharks and holocephalans, such as Etmopterus baxteri, Centroselachus crepidater, and Harriotta raleighana, which have a relatively small telencephalon, a small, smooth cerebellum, and a large medulla, particularly the areas that receive electroreceptive and lateral line input. We hypothesize that a combination of phylogenetic and ecological pressures is contributing to brain development in these species.
0553 AES Morphology, 552 AB, Sunday 11 July 2010
Jessie Waitt1, Michelle Degnin1, John F. Morrissey1, Donna M. McLaughlin2
1Sweet Briar College, Sweet Briar, VA, United States, 2Central Virginia Community College, Lynchburg, VA, United States
Morphological Variation of the Placoid Scales and Teeth of Chain Catsharks, Scyliorhinus retifer: The Influence of Body Location, Age, and Sex
The morphology of placoid scales and teeth of elasmobranchs has long been viewed as being of taxonomic and phylogenetic importance. Unfortunately, an appreciation for morphological variation of these structures due to differences in sex, age, or anatomical position has not been achieved. In an effort to document this variation in chain catsharks (Scyliorhinus retifer), samples of placoid scales were taken from 19 body locations of both sexes at all ages (neonate through adult) and examined with a scanning electron microscope. Similarly, teeth from both jaws of both sexes at all ages (neonate through adult) were examined via light and scanning electron microscopy. Substantial and significant morphological differences due to age, sex, and anatomical position were found in both the placoid scales and teeth of this shark. The easily demonstrable variation in these hard parts is contextualized in terms of swimming behavior, dietary shifts during ontogeny, and systematics.