ANDERSON, JAMES; QUEIROZ, LUISA; HOLLAND, KIM. 2014
(JA) Department of Biology, University of Hawai’i at Manoa, Honolulu, Hawai’i, USA; (LQ) Laboratório de Oceanografia Pesqueira, Universidade Federal Rural de Pernambuco, Recife, Pernambuco, Brazil; (KH) School of Ocean and Earth Science and Technology, University of Hawai’i at Manoa, Honolulu, Hawai’i, USA
Perception and Discrimination of Magnetic Fields in Sandbar (Carcharhinus plumbeus) and Scalloped Hammerhead (Sphyrna lewini) Sharks
It is well documented that a diverse number of species across a broad range of taxa gain positional information and navigate using the earth’s magnetic field. Yet empirical data regarding such capabilities in elasmobranch fishes is remarkably scant, with questions arising over the exact nature of the perceived stimulus. Thus questions regarding if, and how sharks perceive magnetic fields remain unanswered. Here we present some preliminary information from ongoing behavioral studies investigating the ability of two shark species to perceive and discriminate magnetic fields. Captive sharks (n=11) were used in two separate studies. Sharks were conditioned through pairing activation of a magnetic stimulus with presentation of food over a target, or by pairing activation of an auditory stimulus with the presentation of food over an electromagnetic target. The conditioned response (CR) in both studies requires sharks to swim to the target in anticipation of reward (food). In study 2, sharks were requires to demonstrate a conditioned response and also choose the correct target to receive the reward. Sharks in study 1 demonstrated a strong response to the magnetic stimulus, making significantly more approaches to the target (P<0.01) during stimulus activation (S+) than before or after activation (S-). Data from study 2 indicates sharks are able to distinguish between magnetically active (S+) and inactive (S-) targets to receive a food reward. These data demonstrate that sharks of different species and life history can detect and use magnetic stimuli in search behavior, supporting hypotheses that sharks navigate using geomagnetic fields.
ARI, CSILLA. 2014.
(AC) University of South Florida, Tampa, Florida, USA, Manta Pacific Research Foundation, Kona, Hawaii, USA, Foundation for the Oceans of Future, Budapest, Hungary
Rapid and Long-term Coloration Changes of Manta Rays (genus Manta)
Changes of body coloration have not been described in manta rays (genus Manta) so far, therefore their natural body coloration is used to distinguish species and their ventral spot markings are used to identify individuals worldwide in order to estimate their population size or seasonal migration. This report describes the first evidence of rapid and long term coloration changes of manta rays based on observations of captive individuals. Rapid body coloration changes were observed most intensely on the dorsal surface and on the head, which occurred within minutes prior to feeding and during intense social interactions. Long term coloration changes were documented on the side of the head, the inner side of the cephalic lobes, the pectoral fin margin of ventral side, and spot markings on the gill slits which appeared within 9 months, most likely during maturation. This observational study confirms the ability of manta rays to rapidly change body coloration during exposure to certain environmental stimuli, as well as that some coloration patterns of manta rays are not as stable over longer periods of time as it has been assumed previously. Understanding the dynamics of these coloration changes is essential for accurate species and individual identification and to perhaps gain insight into more advanced forms of communication.
AIR, CSILLA; D’AGOSTINO, DOMINIC. 2014.
(AC,DD) University of South Florida, Tampa, USA; (AC) Foundation for the Oceans of the Future, Budapest, Hungary
Contingency Checking and Self-Directed Behaviors in Giant Manta Rays: Do Fish Have Self-Awareness?
Elaborate cognitive skills arose independently in different taxonomic groups. Self- recognition is conventionally identified by the understanding that one’s own mirror reflection does not represent another individual but oneself, which has never been proven in any fish species so far. Manta rays have high encephalization quotient similarly to those species that passed the mirror self recognition test and possess the largest brain of all fish species, therefore mirror exposure experiments were conducted on two captive giant manta rays to document their response to their mirror image. The present study shows evidence for manta rays contingency checking and self-directed behavior when exposed to a mirror, which are prerequisites of self-awareness, while these behaviors have been taken as evidence of self-recognition in apes. We conclude that manta rays are likely the first fish species described to exhibit self awareness which implies their ability to higher order brain function, sophisticated cognitive and social skills.
BANGLEY, CHARLES; RULIFSON, ROGER. 2014.
(CB,RR) East Carolina University, Greenville, North Carolina, USA
Sharks in the Sound: Delineating Potential Coastal Shark Habitat Within Pamlico Sound, North Carolina
Coastal sharks often use estuarine environments as nursery habitat, making them potentially vulnerable to human activity. Pamlico Sound is part of the second-largest estuary system in the United States, but relatively little is known about its use by coastal sharks. To identify potential shark habitat areas within the Pamlico Sound, environmental and shark catch data were taken from North Carolina Division of Marine Fisheries (NCDMF) gillnet and longline surveys covering February-December 2007- 2013. A total of 7,521 gillnet and 631 longline sets captured 2,299 individual sharks representing 11 species. All sampling locations were plotted in Arc-GIS and distance to the nearest inlet and known SAV bed were determined for each station. Environmental and spatial factors potentially affecting shark abundance were interpolated and converted into raster layers covering the area of Pamlico Sound. For each species, multiple regression analysis was used to determine which of these factors most strongly correlated with abundance. These factors were run through classification and regression tree (CART) models to identify environmental “break points” between high and low catches. Areas of Pamlico Sound falling within these environmental parameters were mapped to delineate the spatial extent of potential habitat for each shark species within the estuary.
BARBINI, SANTIAGO; LUCIFORA, LUIS; FIGUEROA, DANIEL. 2014.
(SB,DF) LAboratorio de Ictiología, Instituto de Investigaciones Marinas y Costeras, CONICET- UNMdP, Mar del Plata, Argentina; (LL) Instituto de Biología Subtropical – Iguazú, Universidad Nacional de Misiones, Puerto Iguazú, Argentina
Using Opportunistic Records from a Recreational Fishing Magazine to Assess Population Trends of Sharks
Detecting and determining changes in the occurrence and abundance of species is prioritary for effective management of the resources and conservation of the biodiversity. In the absence of long-term monitoring data, potential population declines may be very difficult to establish. Therefore, alternative information on occurrence of species to infer population trends is highly valued. We reviewed records of sharks (i.e. Notorynchus cepedianus, Carcharias taurus, Galeorhinus galeus and Carcharhinus brachyurus), from a recreational fishing magazine (Weekend) off northern Argentina, between 1973 and 2008, with the aim of evaluating population trends with opportunistic data sources. For each shark species, the number of occurrences per year in the magazine was registered. Our analyses were based on a non-probabilistic method (McPherson & Myers’ approach) designed to determine population trends with opportunistic sighting records. In this approach we included the number of classified offering fishing guide services published per year in the magazine, as a measure of observation effort. Alike, for each species, we fitted generalized linear models with a Poisson error structure and a log link, where response variable was the number of occurrences per year, the explanatory variable was the year and the logarithm of the number of fishing guide ads was specified as an offset in each model. For both approaches, our models estimated that populations of the four shark species have suffered declines. Estimates produced by these models will help to determine the magnitude of population changes where a paucity of data prevents more precise analysis.
BEDORE, CHRISTINE; KAJIURA, STEPHEN; JOHNSEN, SÖNKE. 2014.
(CB,JS) Duke University, Durham, NC, USA; (SK) Florida Atlantic University, Boca Raton, FL, USA
Bioelectric Crypsis in Cephalopods Reduces Detection by Shark Predators
The ability of cephalopods to camouflage themselves is well documented as a defense against predation. However, visual camouflage is only effective against visually- oriented predators. For example, bioelectric cues that arise from the rhythmic exposure of mucous membranes, such as gills, may make certain animals vulnerable to detection by elasmobranch predators. Thus, modulation of an organism’s own bioelectric field in response to predator stimuli may decrease the risk of predation, which has been suggested for egg-encapsulated elasmobranchs that suspend their ventilatory movements in the presence of predator-simulating electric fields. We used behavioral and physiological assays to assess the freeze response in the cuttlefish, Sepia officinalis, and its effect on detection by sharks. Sepia officinalis ceased ventilation for a period of 2- 37s in response to a video simulation of a looming fish predator. The freeze response resulted in a 45±17% decrease in voltage relative to the surrounding seawater (N= 15, P=0.015). Escape by jetting was also observed, and resulted in a 420±240% increase in voltage. Dipole electric fields that simulated S. officinalis resting, freezing, and jetting were produced with underwater electrodes in a behavioral assay to quantify the detectability by shark predators. Blacktip sharks, Carcharhinus limbatus, and bonnethead sharks, Sphyrna tiburo, responded to freeze stimuli less frequently than resting and jetting (N=534 responses; P<0.001). These results suggest the freeze response facilitates predator avoidance via reduction of sensory stimuli, including bioelectric fields, and future work should examine the extent to which other cues are modulated during this behavior.
BELLEGGIA, MAURO; FIGUEROA, DANIEL E.; MASSA, ANA; BURGESS, GEORGE; BREMEC, CLAUDIA. 2014.
(MA) Instituto Nacional de Investigación y Desarrollo Pesquero, Mar del Plata, Argentina; (MB,CB) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; (DEF) Laboratorio de Ictiología, FCEyN, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina; (GB) Florida Museum of Natural History, University of Florida, Gainesville, FL, USA
The Diets of the Spiny Dogfish Species (Squalus acanthias, S. mitsukurii and S. cubensis) From the Northern Argentinean Continental Shelf
In the southwest Atlantic Ocean inhabit three Squalidae species: Squalus acanthias, S. cubensis and S. mitsukurii. In spite of the diet of the former having been widely studied in Argentina and worldwide, the trophic ecology of S. cubensis and S. mitsukurii remain unknown. In this context the diets of these two species were studied based on analysis of stomach contents from specimens caught during three research cruises on the northern Argentinean continental shelf (34o S – 41o S). Prey items were identified to the lowest possible taxonomic level, counted and weighted. A total of 214 specimens of S. cubensis were analyzed from which 176 (82.24%) contained prey items. From 414 specimens of S. mitsukurii analyzed, 289 (69.80%) contained food in their stomachs. Squalus mitsukurii fed on fish (%IRI=54.1%), crustaceans (%IRI=25.04%) and cephalopods (%IRI=18.89%). The argentine anchovy Engraulis anchoita, the argentine hake Merluccius hubbsi and hagfishes Mixinidae were among the most important identified fishes. The euphausiids were the most consumed crustaceans, whereas Illex argentinus, Loligo sanpaulensis were the preferred cephalopods. On the other hand, the diet of S. cubensis was composed mostly by fishes (%IRI=84.96%), followed by crustaceans (%IRI=9.99%) and cephalopods (%IRI=1.99%). The most important prey items identified in the diet of S. cubensis were the same as those found in S. mitsukurii, but differed in proportions. The hypotheses that the diet is determined by intrinsic (total length, sex, maturity) and extrinsic factors (area, season) were tested by fitting generalized linear models (GLMs).
BENENTT, BRENT; BRUEMMER, SARAH; GARDINER, JAYNE; BEDORE, CHRISTINE. 2014.
(CB) Duke University, Durham, NC, USA; (BB) Principia College, Elsah, IL, USA; (SB,JG) Mote Marine Laboratory, Sarasota, FL, USA
Scaling of the Elasmobranch Electrosensory System and Effects on Behavioral Responses to Prey-simulating Electric Fields
Sharks detect changes in voltage (electric field gradient) with specialized receptors called ampullae of Lorenzini, which terminate at the skin surface in an array of pores. Pore distribution and density differ for each elasmobranch species. Higher pore density has been hypothesized to be associated with higher resolution, similar to increasing pixels on a camera. Pore number does not change over ontogeny so larger animals may have lower resolution. Gel-filled canals that connect pores to the subdermal receptor elongate with growth, which is thought to increase sensitivity. Therefore, as a shark grows, it may lose spatial resolution capabilities, but may increase in sensitivity. We used a behavioral assay to quantify sensitivity of adult bonnethead sharks, Sphyrna tiburo (N=9), to weak electric fields, as well as quantify their accuracy (as a proxy for resolution) in localizing the source of the electric stimulus. Our data were compared to those published on neonate bonnethead sharks to determine if sensitivity or resolution are affected by growth. Both neonate and adult sharks demonstrated a behavioral electrosensitivity of approximately 50 nV cm-1, but neonate sharks were more accurate in locating the electric stimulus than adult sharks. Our results suggest that changes in peripheral morphology over ontogeny do affect behavioral responses by reducing resolution. Although not quantified here, adult bonnethead sharks may compensate for the reduction in resolution by enlarging their electrosensory search area as the surface area of their heads increase with growth.
BETHEA, DANA; AJEMIAN, MATTHEW; CARLSON, JOHN; HOFFMAYER, ERIC; IMHOFF, JOHANNA; GRUBBS, R. DEAN; PETERSON, CHESTON; BURGESS, GEORGE. 2014.
(DB,JC) NOAA NMFS SEFSC, Panama City, FL, USA; (MA) Texas A&M University Harte Research Institute, Corpus Christi, TX, USA; (EH) NOAA NMFS SEFSC, Pascagoula, MA, USA; (JH,DG,CP) Florida State University Coastal & Marine Laboratory, St. Teresa, FL, USA; (GB) The University of Florida Florida Museum of Natural History, Gainesville, FL, USA
Distribution and Community Structure of Coastal Sharks in the Northeastern Gulf of Mexico
Coastal shark community structure was quantified across 10 geographic areas in the northeastern Gulf of Mexico using fishery-independent gillnet data from 2003-2011. A total of 3,205 sets were made in which 14,244 carcharhiniform sharks, primarily juveniles, were caught comprising 11 species from three families. Atlantic sharpnose sharks (Rhizoprionodon terraenovae) were the most abundant species overall followed by bonnethead (Sphyrna tiburo) and blacktip sharks (Carcharhinus limbatus). Two-way crossed analysis of similarity (ANOSIM) found geographic area to significantly influence shark species-life stage assemblages while season did not. Resemblance matrices between environmental data and shark community assemblage found the two were significantly correlated with the combination of salinity and turbidity producing the highest Spearman rank correlation value. Species diversity varied by geographic area, but was generally highest in areas with the greatest amount of fresh and saltwater fluctuations. The mean size of the three most abundant species differed across geographic areas; whereas, those species in lower abundances also differed across regions, but exhibited no discernible pattern. Our results suggest geographic area is important for juvenile sharks and some areas may be considered important nursery areas for many species. Atlantic sharpnose and blacktip shark were not restricted to any specific geographic area but species such as bull (C. leucas), spinner (C. brevipinna), blacknose (C. acronotus), finetooth (C. isodon), sandbar (C. plumbeus) and scalloped hammerhead (S. lewini) sharks were only consistently captured within a single area or over a select group of areas.
BIZZARRO, JOSEPH; BROMS, KRISTEN; LOGSDON, MILES; EBERT, DAVID; YOKLAVICH, MARY; KUHNZ, LINDA; SUMMERS, ADAM. 2013.
(JB,ML,AS) University of Washington, Seattle, WA, USA; (KB) Colorado State University, Fort Collins, CO, USA; (DE) Moss Landing Marine Laboratories, Moss Landing, CA, USA; (MY) National Marine Fisheries Service, Santa Cruz, CA, USA; (LK) Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
Spatial Segregation in Eastern North Pacific Skate Assemblages
Skates (Rajiformes: Rajoidei) are common mesopredators in marine benthic communities, yet the spatial associations of individual species and the structure of skate assemblages are poorly known. Such information is of considerable importance for monitoring and management of exploited skate populations. This study investigated the spatial associations of eastern North Pacific skate assemblages in continental shelf and upper continental slope waters of California and the western Gulf of Alaska. Long– term fishery independent data were analyzed using spatial analysis techniques and regression models to determine distribution (by depth, temperature, and latitude/longitude) and relative abundance of the dominant species in each region. Submersible video data also were incorporated in California to facilitate habitat association analysis. Skate populations were highly clustered in both regions, on scales of 10s of kilometers; however, high–density regions were largely segregated among species. In general, skate densities and frequency of occurrence was substantially reduced in Alaska as compared to California. Although skates are typically believed to be restricted to soft sediment regions, R. rhina exhibited the strongest habitat association with mixed substrates, and R. stellulata catches were greatest in association with rocky reefs. In regions where species overlapped substantially in geographic and depth distribution (e.g., R. rhina and B. kincaidii in Monterey Bay, CA; B. aleutica and B. interrupta in Shelikof Strait), size segregation was evident. Spatial niche differentiation in skates appears to be more pronounced than previously reported.
BREWSTER, LAURAN; GUTTRIDGE, TRISTAN; BULLOCK, ROBET; GRUBER, SAMUEL; GLEISS, ADRIAN; WHITNEY, NICHOLAS. 2014.
(LB,T,RB,SG) Bimini Biological Field Station Foundation, Miami, FL, USA; (AG) Hopkins Marine Station, Pacific Grove, CA, USA; (NW) Mote Marine Laboratory, Sarasota, FL, USA
Accelerometery to Determine the Field Metabolic Rate of Marine Predators
The evolvement and miniaturization of bio-logging technology plays a pivotal role in elucidating the cryptic lives of animals in their natural environment. Accelerometers allow for formerly unattainable interpretation of fine-scale behaviors, addressing important questions regarding activity levels and energetic requirements. Ascertaining field metabolic rate (FMR) is essential for quantifying the impact of a species on its ecosystem and producing reliable bioenergetics models for fisheries management. Acceleration data has been collected for two free-living model species: G. cirratum (<90cm Total Length; n=4 dry season, n=3 wet season) and N. brevirostris (n=3 dry season, n=9 wet season). Preliminary analysis for G. cirratum data allowed us to characterize behaviours such as resting and steady swimming with fast-start swimming additionally identified for N. brevirostris. For G. cirratum, analysis showed that on average 87.70% ±1.52 (mean ±SE) and 86.73% ±3.02 of the time was spent resting during the dry and wet season respectively. N. brevirostris averaged 10.83% ± 1.97 and 15.74% ± 3.26 of their time resting during wet and dry seasons respectively; 89.04% ± 1.97 and 84.17% ± 3.26 steady swimming. Overall Dynamic Body Acceleration (ODBA) values for each species have been determined for different behaviours. An individual of G. cirratum experienced a range of values from 1.19×10-7g for resting to 8.32g for fastest swimming. This ongoing study is expected to demonstrate a revolutionary technique in determining FMR in marine predators. These field data will combine with results of ongoing respirometry experiments to correlate ODBA and MO2 to determine the FMR of these species.
BROWN, AMANDA; GELSLEICHTER, JIM. 2014
University of North Florida, Jacksonville, FL, USA
Reproductive Endocrinology of the Finetooth Shark, Carcharhinus isodon
The finetooth shark, Carcharhinus isodon, is a small coastal shark found in Atlantic waters from South Carolina to Florida. Due to recent fishing pressures, new reproductive data is being gathered in order to reassess the status of the fishery. This provided an opportunity to examine the reproductive endocrinology of C. isodon, and explore how gonadal sex steroids may contribute to the regulation of reproduction. Plasma serum concentrations of the sex steroids testosterone (T) in males and 17b-estradiol (E2) and progesterone (P4) in females were measured using chemiluminescent assays (CLIA). Histological sections of reproductive organs such as the testis, ovary, uterus and oviducal gland were prepared and used to characterize changes in tissue architecture and identify target cells for sex steroid action using immunocytochemistry. Plasma T concentrations in males peaked in Spring followed by a rapid decline in May prior to the mating season indicating a key role of androgens in spermatogenesis. Histological analysis of the testis confirms this pattern, demonstrating the presence of mature spermatozoa in Spring samples. In females, E2 levels were highest in vitellogenic females and lowest in gravid, non vitellogenic females suggesting that this hormone plays a key role in yolk production and follicular development. Histological analysis shows the presence of yolk in females with high E2 levels. Hormone data is being compared with hormone receptor localization to provide data on the role of these hormones in reproductive cycling.
BROWN, AMANDA; GELSLEICHTER, JIM; FRAZER, BRYAN. 2014.
(AB,JG) University of North Florida, Jacksonville, FL, USA (BF) South Carolina Department of Natural Resources, Charleston, SC, USA
The Reproductive Biology of the Finetooth Shark, Carcharhinus isodon, in the Northwest Atlantic Ocean
The finetooth shark is a small coastal shark species found in Atlantic waters from South Carolina to Florida. This species has recently come under increased fishing pressure and has previously been designated as “overfished.” New life history and reproductive biological data is required so that these populations can be properly managed. To address this issue, this study will examine the reproductive biology of Atlantic finetooth sharks. Morphological measurements of reproductive organs were obtained throughout the year to determine reproductive timing. Histological analysis was conducted on gonads of mature animals to determine reproductive stage. Plasma concentrations of the sex steroids testosterone in males and 17b-estradiol in females were also measured as these hormones are good indicators of reproductive condition. In males, testis and head epididymis width increases starting in September and peaks in late April/early May, followed by a rapid decline. Histological analysis of the testis showed the presence of mature spermatozoa in Spring samples directly prior to copulation, indicating this is the period of spermatogenesis. Plasma testosterone concentrations in males also peaked in Spring followed by a rapid decline in May corroborating histological data. In females, follicle diameter was greatest from winter- early Spring, indicating that this is the period of vitellogenesis. Estradiol levels were highest in vitellogenic females and lowest in gravid females. Follicular diameter decreased after late Spring, suggesting that this is the period of ovulation and fertilization. Embryos were present in only non-vitellogenic females, suggesting a biennial reproductive strategy. Average litter size is 4-6 pups/litter.
BULLOCK, ROB; BREWSTER, LAURAN; BOND, MARK; GUTTRIDGE, TRISTAN; GRUBER, SAMUEL.
(SG) Bimini Biological Field Station Foundation, Bimini, Bahamas; (RB,LB) University of Hull, Hull, England, UK; (MB) Stony Brook University, Stony Brook, New York, USA; (TG) Cardiff University, Cardiff, Wales, UK
Assessing the Effects of Prey Interactions on Habitat Use Patterns and Foraging Effort in Lemon Sharks
Coastal nursery sites provide critical refuge for young sharks. Delineating how sharks use these habitats and interact with other species helps us to better understand their ecological role and develop sound marine management policy. In this ongoing study we assess the effects of distribution and abundance of prey species on lemon shark behaviour, in Bimini, Bahamas. For this study we developed a ‘tag package’ comprised of a CEFAS G6A tri-axial accelerometer and a Sonotronics PT4 acoustic transmitter. Tag packages are attached to the first dorsal fin of sharks. Accelerometers provide quantitative behavioural data used to identify potential foraging attempts and acoustic transmitters are used to actively track large juvenile (0.8-1.2m) and sub-adult (1.2-2.0m) lemon sharks. We surveyed the study site for potential prey communities using baited remote underwater video stations (BRUVS). Thus far 12 sharks have been tagged for periods ranging 3 to 5 days. Accelerometer and telemetry data show distinct, tidally mediated patterns in diel movements and foraging effort in lemon sharks. Relative abundance data from 150 BRUVS deployments show abundance and distribution of prey species to vary greatly within the study site. We aim to identify overlap between patterns in shark movements and foraging effort with prey availability, demonstrating the importance of predation and inter-species interactions in the daily habitat use patterns of lemon sharks. This research is supported by a grant from the Bimini Biological Field Station Foundation.
CAILLIET, GREGOR; GOLDMAN, KENNETH; MOLLET, HENRY. 2014.
(GC,HM) Moss Landing Marine Laboratories, Moss Landing, CA, USA; (KG) Alaska Department of Fish and Game, Homer, AK, USA; (HM) Monterey Bay Aquarium, Monterey, CA, USA
The Use of Demographic Parameters to Assess the Population Size of Shark Species: A Test Case Using the White Shark (Carcharodon carcharias) Sub- population off Central California, USA
We explore the use of demographic parameters to assess the size of shark populations. We have chosen white sharks (Carcharadon carcharias) off central California because recent studies have provided usable data. White sharks are difficult to sample because they are highly migratory, move both vertically and horizontally, and tend to segregate by sex, age and size. Thus, their population or sub-population sizes are difficult to estimate. A recent tag-recapture study used photographic identification of the trailing edge of the first dorsal fin and concluded that the central California sub-population comprises only 219 sub-adult and adult white sharks. We use a dataset from sharks observed in that study to generate an estimate of total population size using demographic modeling. Our results indicate that an all-life-stage sub-population size of
>2,400 individuals in coastal California is required to account for the abundance of the 219 adults and sub-adults of white sharks estimated in the previous central California study. Our estimate concurs with those of recent state and federal panel assessments of ESA status. The true total white shark population size throughout the eastern North Pacific is likely several-fold greater than both our study and the original published estimate because they both exclude non-aggregating, or otherwise unobservable, sharks, and those that independently aggregate at other important eastern North Pacific sites. Accurately estimating total population sizes of sharks requires methodologies that account for biases introduced by sampling a limited number of sites and include all life history stages across the species’ range.
CAMARGO, SÂMIA M.; FERRETTE, BRUNO L.S.; SILVA, GUILHERME C.; OLIVIERA, CLAUDIO; MENDES, NATÁLIA J; SANTOS, MIGUEL N.; COEHLO, RUI; FORESTI, FAUSTO; MENDONCA, FERNANDO F.. 2014.
(SMC,MFF) Laboratório de Genética Pesqueira e Conservação, Departamento de Ciências do Mar, Universidade Federal de São Paulo, Campus da Baixada Santista, Santos/SP, Brazil; (SMC,BLSF,GCS,CO,NJM,FF) Laboratório de Biologia e Genética de Peixes, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Campus de Botucatu, Botucatu/SP, Brazil; (MNS,RC) Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, Faro, Portugal; (RC) Instituto Português do Mar e Atmosfera, Olhão, Portugal
Phylogeography of the Oceanic Whitetip Shark Carcharhinusn longimanus in the Atlantic Ocean, Using Molecular Markers
The oceanic whitetip shark Carcharhinus longimanus have been considered one of the most important capture species of commercial interest, which currently have strong signs of population depletion. Considering that, researches on the genetic structure of fish populations have contributed to clarify issues relating to population genetic variability, distribution, migration, taxonomy, systematic and historical events. Additionally, considering the urgent need for effective conservation plans for this species, this study aims to characterize the genetic structure of population of the oceanic whitetip shark in the Atlantic Ocean, using sequences of the mitochondrial DNA control region. A review of 100 individuals captured in localities nearby the African continent and the Brazilian coast were characterized with 658 analyzed nucleotide bases with the identification of 6 polymorphic sites forming 8 distinct haplotypes. The total nucleotide diversity was π = 0.00089 and haplotype diversity was Hd = 0.338, which are similar to the rates found in other shark species analyzed with the same markers. In the Analysis of Molecular Variance was observed a moderate population structure (FST = 0.10436) with moderate level of restriction to gene flow between the West and East Atlantic. It must be considered that this index of divergence between the sample groups do not characterize genetically distinct stocks, but for the development of conservation plans aimed to safeguarding the genetic variability of C. longimanus is necessary giving priority to management areas where unique haplotypes were identified, attributing high genetic diversity to these regions.
DA SILVA, JOAO PAULO CAPRETZ; DE CARVALHO, MARCELO R.. 2014.
Instituto de Biociencias, Sao Paulo, SP, Brazil
A Reinterpretation of the Pectoral Articulation in Elasmobranchs (Chondrichthyes)
The morphology of the pectoral articular region in elasmobranchs was studied based on 154 species from 97 genera representing many orders and families. Particular attention was given to characters employed in previous higher-level morphological phylogenetic studies. Two characters of the pectoral articulation previously described in these studies as presenting non-homoplastic distributions are reported here to be more complex in variation and distribution (a separate articular condyle for the pectoral metapterygium and the presence of an articular condyle for the pectoral propterygium). These characters provide new insights concerning the higher-level relationships of elasmobranchs. This study highlights the continued importance of morphological characters for phylogenetic analyses and that certain characters employed in higher- level phylogenetic studies of elasmobranchs need to be revised.
CECIL, STACY L.; MORRISSEY, JOHN F., FELDHEIM, KEVIN A.; DALY-ENGEL, TOBY S.. 2014.
(SLC, TSD) University of West Florida, Pensacola Florida, USA (JFM) Sweet Briar College, Lynchburg, Virginia, USA; (KAF) The Field Museum, Chicago, Illinois, USA
Development and Optimization of Novel Microsatellite Loci for the Chain Catshark, Scyliorhinus retifer
The chain catshark, Scyliorhinus retifer, is a small, oviparous, shark species commonly used by humans in the aquarium trade. Abundant and relatively easy to study, S. retifer provides a unique opportunity to examine elasmobranch mating strategies. Whether viviparous or oviparous, most elasmobranch species show evidence of polygyandry, promiscuous mating by both sexes. Usually polygyandry is indicated by molecular studies identifying multiple paternity, which occurs when a single litter of offspring is sired by multiple males. Multiple paternity appears to have little benefit to female sharks across taxa, and speculation varies as to why they consistently endure multiple mating events. Genetic tools, such as microsatellites, have been used effectively in previous studies on sharks for describing multiple paternity as a genetic mating system. This study describes the optimization of novel, species-specific microsatellite markers for use in S. retifer, with potential for cross amplification to related species. Of the 34 loci tested, 19 amplified consistently and showed enough allelic polymorphism to be useful for determining multiple paternity. Because of fishing pressure and habitat loss for many elasmobranchs, understanding shark mating behaviors in species such as S. retifer allows for better management and conservation practices in other at risk elasmobranchs.
CHABOT, CHRIS; BUTH, DONALD. 2014.
(CC) California State University (CSUN), Northridge, CA 91330-8303, USA; (DB) University of California (UCLA), Los Angeles, CA 90095-1606, USA
Species-specific Nuclear Genetic Markers for the Detection of Hybridization Between the Grey Smoothhound (Mustelus californicus) and the Brown Smoothhound (Mustelus henlei)
Many species retain the physiological capacity to hybridize over long periods of evolutionary time. Hybridization has been reported recently for the first time within sharks and may be the reason for uncertainty regarding phylogenetic relationships within the genus Mustelus. Because of similar life-histories and morphologies, limited genetic divergence (both nuclear and mitochondrial DNA), and the degree of uncertainty regarding their phylogenetic relationship, 31 allozyme loci were used to determine the levels of genetic diversity for the grey smoothhound, Mustelus californicus, and the brown smoothhound, M. henlei, and to detect species-specific nuclear markers capable of determining the existence of hybridization within northeastern Pacific Mustelus. Tissue extracts from 26 adult M. henlei collected from Santa Catalina Island, CA and 17 M. californicus collected from Marina Del Rey, CA were subjected to starch gel electrophoresis. Gene products of the loci were resolved for both species. All 31 loci were monoallelic in M. californicus, whereas polymorphic loci, two diallelic and one triallelic, were resolved in M. henlei. Nine of the 31 loci exhibited complete allelic divergence between the two species, i.e. no shared alleles, and can serve as diagnostic markers to reveal potential hybrids.
CHABOT, CHRIS; ESPINOZA, MARIO; OSORIO, ISMAEL M.; ROCHA-OLIVARES, AXAYACATL. 2014.
(CC) California State University, Northridge, Northridge, CA, USA; (ME) Universidad de Costa Rica, San José, Costa Rica; (IMO) Centro para la Biodiversidad Marina y la Conservación A.C., La Paz, Baja California Sur, Mexico; (ARO) Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, Mexico
Population Structure and Gene Flow in the Brown Smoothhound Shark, Mustelus henlei, in the Northeastern Pacific
We assessed the effects of the prominent biogeographic (Point Conception and the Peninsula of Baja California) and phylogeographic barriers (Los Angeles Region) of the northeastern Pacific on the population connectivity of the brown smoothhound shark, Mustelus henlei (Triakidae), using data from the mitochondrial control region and six nuclear microsatellite markers to measure gene flow among sample localities from throughout the range of the species (San Francisco Bay, CA, Santa Barbara, CA, Santa Catalina Island, CA, Punta Lobos, Baja California Sur, San Felipe, Baja California, Mexico, and Costa Rica). Mitochondrial and microsatellite data revealed significant population structure among three populations: northern (San Francisco), central (Santa Barbara, Santa Catalina, Punta Lobos, and San Felipe), and southern (Costa Rica).
Patterns of long-term and contemporary migration were incongruent, with long-term migration being asymmetric and occurring in a north to south direction and a lack of significant contemporary migration observed between localities with the exception of Punta Lobos that contributed migrants to all localities within the central population.
Our findings indicate that Point Conception may be restricting gene flow between the northern and central populations whereas barriers to gene flow within the central population would seem to be ineffective; additionally, a contemporary expansion of tropical M. henlei into subtropical and temperate waters in response to climate change may have been observed.
CHIERICHETTI, MELISA; SCENNA, LORENA; FIGUEROA, DANIEL; ONDARZA, PAOLA; MIGLIORANZA, KARINA; DE GIÁCOMO, EDUARDO. 2014.
(MC,LS,DF) Laboratorio de Ictiología, Instituto de Investigaciones Marinas y Costeras (IIMyC), Universidad Nacional de Mar del Plata (UNMdP), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina; (PO,KM) Laboratorio de Ecotoxicología y Contaminación Ambiental, IIMyC, UNMdP, CONICET, Mar del Plata, Argentina; (EG) Grupo CONDROS, Instituto de Biología Marina y Pesquera “Alte. Storni”, San Antonio Oeste, Argentina
Reproductive Biology of the Cockfish, Callorhinchus callorynchus (Holocephali: Callorhinchidae), in a Coastal Area off Argentina
The knowledge of reproductive parameters is needed to assess the status of the populations and to develop effective fisheries management plans. The cockfish, Callorhinchus callorynchus, is an oviparous species of chondrichthyans widely distributed in the Southwest Atlantic (23°-55° S). This species has come under increased fishing pressure on the Argentinean Continental Shelf (34o-55oS), being an important resource for artisanal, commercial and recreational fisheries. However, the life-history characteristics of C. callorynchus have been only studied in the northern Patagonia (41o- 42o S, 64-65oW). Therefore, we investigated the reproductive biology of this species in coastal area of Argentinean Shelf (36o-37oS) that supports a high fishing pressure on chondrichthyans. A total of 6 males (385-455 mm precaudal length, PCL) and 143 females (390-630 mm PCL) were collected from small-scale artisanal fishermen catch at depths lower than 50 m, during winter-spring from 2011 to 2013. Males had secondary sexual structures (frontal tenaculum and prepelvic claspers), which would be utilized during mating. The smallest mature female measured 410 mm PCL, whereas the largest immature one was 490 mm PCL. The length at 50% maturity in females was 465 mm, which corresponded to 74% PCL of the largest female sampled. There was no seasonal variation in average number of mature oocytes. Although the highest values of gonadosomatic and liver indices were recorded in October and November (spring), females with eggs cases in their uterus were not found in the study area, suggesting that it would be not a spawning zone for the species.
CHRISTIANSEN, HEATHER M.; HUSSEY, NIGEL E.; CLIFF, GEREMY; WINTNER; SABIN P.; DUDLEY, SHELDON F.J.; FISK, A.T.. 2014.
(HMC,NEH,ATF) Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada; (GC,SPW) KwaZulu-Natal Sharks Board, Umhlanga Rocks, South Africa; (GC,SPW) Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa; (SFLD) Department of Agriculture, Forestry and Fisheries, Cape Town, South Africa
Investigating Within and Among-individual Variation in the Trophic Ecology of the Marine Apex Predator White Shark, Carcharodon carcharias
Understanding a species’ diet is important to elucidate its connectivity and role within food webs. Given the wide range of prey available to top predators, complex food web linkages often occur within populations confounding our understanding of their trophic roles. Moreover the occurrence of diet specialization or ecotypes within top predator species is likely common but to date has received only limited attention. White sharks (Carcharodon carcharias) are apex predators, with documented diet shifts with increasing size and consumption of a diverse prey base. To investigate variability in the diet of white sharks off southern Africa, we measured δ13C and δ15N values in tissues sampled from juvenile and sub-adult white sharks (200-300 cm total length, TL) that have defined habitat and migration patterns. Multiple tissue types with different turnover rates were analyzed to provide insight into feeding behaviors over spatio-temporal scales. Among individual variation differed by tissue, with stable isotope values ranging by 3.2, 2.7, and 3.7‰ (δ13C) and 5.8, 2.2, and 3.0‰ (δ15N) for vertebrae, muscle, and fin tissues, respectively. Furthermore, vertebrae were sequentially sampled providing an indication of within individual changes in isotope values over ontogeny. Within individual variation was 1.0 ± 0.6‰ (range, 0.01-2.6‰) (δ13C) and 2.2 ± 1.0‰ (range, 0.01-4.7‰) (δ15N). These data indicate spatio-temporal variation in feeding behaviors (i.e., diet and habitat use) of and between individual white sharks. Data on the variable contributions of the main prey groups to juvenile/sub-adult white sharks will be presented as well as investigations of diet by sex.
CLINGHAM, ELIZABETH; BROWN, JUDITH; DOVE, ALISTAIR, TYMINSKI, JOHN; HUETER, ROBERT. 2014.
(EC,JB) Environmental and Natural Resources Directorate, St. Helena Government, Jamestown, Saint Helena; (AD) Georgia Aquarium, Atlanta, GA, USA; (JT,RH) Center for Shark Research, Mote Marine Laboratory, Sarasota, FL, USA
Observations and First Tagging of Whale Sharks off St. Helena in the South Atlantic
Much is yet unknown about the behavioural ecology and reproduction of the whale shark. An aggregation site for this species has been identified off St. Helena, a remote volcanic island in the South Atlantic Ocean about 3,100 km northwest of Cape Town, South Africa. A total of 286 whale shark sightings by government biologists, fishers and the public were recorded February 1999 – March 2014, with up to 17 sharks observed in a single sighting. Sharks ranged 4 to >10 m estimated total length and were of both sexes. Unlike other whale shark aggregations, this site comprises more females than males, with some of the larger females appearing pregnant. Mature males and juveniles of both sexes also are present. Active ram surface feeding has been observed and plankton analyses in the area reveal large numbers of fish eggs. Observations of pregnant females, possible mating and young juveniles in the area are consistent with the Mid-Ocean Remote Pupping Hypothesis (MORPH) for this species. In January 2014, two possibly pregnant whale sharks were satellite-tagged, one with a floating SPOT5 and one with a PSAT. The SPOT5 remained attached for three weeks and revealed around-island movements and some offshore forays. The PSAT was programmed to report June 2014. With the opening of St. Helena’s first airport scheduled for 2016, conservation measures to protect St. Helena’s whale sharks are in development, given an expected sharp increase in ecotourism on the island.
CORRIGAN, SHANNON; YANG, LEI; LI, CHENHONG; STRAUBE, NICO; LAST, PETER; WHITE, WILL; MARSHALL, LINDSAY; DAVIES, JASON; MAISEY, JOHN; HOFREITER, MICHI; NAYLOR, GAVIN. 2014.
(SC,LY,NS,JD,GN) Hollings Marine Laboratory, College of Charleston, Charleston, SC, USA; (MH) Universität Potsdam, Potsdam, Brandenburg, Germany; (PL,WW) CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia; (CL) College of Fisheries and Life Science, Shanghai Ocean University, Pudong, Shanghai, China; (JM) Deptartment of Paleontology, American Museum of Natural History, New York, New York, USA; (LM) Stick Figure Fish Illustration, Everton Park, Queensland, Australia
The Chondrichthyan Tree of Life Project
The Chondrichthyan Tree of Life Project is a five year, multi-disciplinary, multi- institutional project funded by the U.S. National Science Foundation. Its mission is to document both extant and extinct chondrichthyan diversity and to provide an evolutionary framework for the interpretation of variation within the group. There are four components to the project (A) An up-to-date taxonomic accounting of all extant species including scientific illustrations for each species (B) An estimate of evolutionary relationships based on comparisons of DNA sequences and skeletal anatomy (C) Up-to- date range maps for all described extant species (D) CT scans for representatives of the major lineages for comparative anatomy. In pursuing the project, we have developed a targeted DNA hybridisation sequence capture protocol that allows high throughput DNA sequencing of ~ 1000 nuclear exons and their associated introns for use in phylogenetics and population genetics, technology for the interactive display of geographic range information, technology for the interactive display of comparative anatomy over the world wide web. This presentation will provide an overview of each of these components as well as present some noteworthy results that have emerged from each component of the project thus far.
COTTON, CHARLES F.; GRUBBS, R. DEAN; ROLFE, SHANNON C.; HEIL, AUSTIN. 2014.
(CFC,RDG,AH) Florida State University Coastal and Marine Lab, St. Teresa, FL, USA; (SCR) University of Central Florida, Orlando, FL, USA
Life History Characteristics of Two Common Deep-Water Dogfishes (Squalus cubensis and S. cf. mitsukurii) from the Northern Gulf of Mexico
More than half of all identified shark species reside in deep waters (> 200 m), yet little is known about their life histories due to low fisheries reporting and a paucity of scientific sampling in the deep ocean. In conjunction with a project to examine the ecological effects of the 2010 Deepwater Horizon oil spill (Deep-C; www.deep-c.org), sharks were collected near Desoto Canyon in the northern Gulf of Mexico using demersal longlines in depths of 191 to 2,645 m. Reproductive tracts from 162 Squalus cubensis and 117 S. cf. mitsukurii were collected to determine reproductive parameters (e.g. fecundity, embryonic sex ratio, size-at-maturity) and growth model parameters (e.g. theoretical asymptotic size (Linf), the growth rate constant (k), age-at-maturity). Sexual maturity for males was determined by degree of clasper calcification and vas deferens coiling. Additionally, the inner and outer clasper lengths were measured. In females, maturity was determined by uterine expansion or presence of embryos. The diameter of the largest oocyte was measured to characterize the ovarian cycle and any visible embryos were counted, sexed and measured. Length-based maturity ogives will be constructed to determine sex-specific size at maturity. Fecundity and seasonality of mating was determined for each species and the relationship of maternal size to fecundity was investigated. Sharks were aged by counting growth bands deposited on the enamel caps of both dorsal finspines and growth will be modeled using multiple length-at-age models. These results will inform life history models and fisheries managers in countries currently exploiting these poorly-studied species.
CRAWFORD, CALLIE; CANSTEIN, CHRISTEIN; NAYLOR, GAVIN. 2014.
(CRAWFORD,GN) College of Charleston, Charleston, SC, USA; (CANSTEIN)Siemens Healthcare, CT Division, Forchheim, Germany
CT Scanning Chondrichthyans: No Bones About It
Computed Tomography (CT) imaging is a nondestructive method for viewing internal structures of extant and fossilized specimens. Once CT scan data is acquired, reconstruction programs can be used to manually segment the data into constituent skeletal structures, creating 3-Dimensional representations of the structures which can then be viewed digitally or printed in 3D. The quality and ease of segmentation is tightly tied to the visible contrast between study structures and other tissues in the organism. In most groups of vertebrate organisms, skeletal structures are made of calcified bone which has high radio-opacity, leading to greater contrast between the skeleton and soft tissues. Chondrichthyans (sharks, skates, rays, and chimaeras), by comparison, have skeletons composed of cartilage which is much less radio-opaque than bone, resulting in lower contrast with surrounding tissues. Settings within the CT scanners and the type of scanner can make a large difference in the quality of the scan data. Better scan data will result in more accurate reconstructions of the skeletal anatomy. We will explore the difficulties inherent in CT scanning and segmenting cartilaginous skeletal structures in Chondrichthyan fishes and discuss the differences in single source and dual source Siemens CT Scanning.
CURTIS, TOBEY; HARE, JOHNATHN; KENNEY, ROBERT; ZEEMAN, STEPHAN; SUMMERS, ERIN; SKOMAL, GREGORY. 2014.
(TC) University of Massachusetts – Dartmouth, Fairhaven, MA, USA; (JH) National Marine Fisheries Service, Narragansett, RI, USA; (RK) University of Rhode Island, Narragansett, RI, USA; (SZ) University of New England, Biddeford, ME, USA; (ES) Maine Department of Marine Resources, Boothbay Harbor, ME, USA; (GS)Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
Movements and Habitat Selection of Basking Sharks (Cetorhinus maximus) in Relation to Zooplankton Abundance in the Gulf of Maine
The distribution of prey can significantly influence the movements and habitat selection of predators. However, it is difficult to study prey-influenced habitat selection in the marine environment due to the challenges of simultaneously observing both predators and prey across available habitats. In this study, we examined the distribution and movements of the filter-feeding basking shark (Cetorhinus maximus) in relation to zooplankton abundance in the Gulf of Maine, western North Atlantic Ocean. Shark movements were observed using satellite-linked Smart Position or Temperature transmitting (SPOT) tags (N=10), and additional presence records during the tracking period were collected from routine marine mammal surveys (N=158). Zooplankton abundance landscapes were derived from standardized plankton surveys conducted concurrently with shark tracking. Activity spaces of the tracked sharks were quite small given their highly mobile habits. Basking shark habitat use was non-random with respect to the density of various zooplankton species groups. Sharks tended to select patches with high abundance of certain zooplankton species, but avoided areas with high abundance of others. They effectively tracked the shifting distributions of their preferred prey across seasons, supporting the idea that basking sharks can be considered “biological plankton recorders.” The significance of efficient foraging in this species will be discussed with reference to recent insights into its long-distance seasonal migrations.
DALY-ENGEL, T.; GRUBBS, DEAN; LARSON, SHAWN. 2014.
(TD) University of West Florida, Pensacola, Florida, USA; (SL) Seattle Aquarium, Seattle, Washington, USA; (DG) Florida State University Coastal and Marine Laboratory, St. Teresa, Florida, USA
Phylogeography Across the Global Range of an Ancient Deep-water Predator: the Bluntnose Sixgill Shark (Hexanchus griseus)
The evolutionary processes affecting the population structure of deep-water fishes are poorly understood, as is the potential impact of unprecedented human-mediated climate change on deep-ocean environments. We used mixed-marker analysis to examine the molecular ecology of the bluntnose sixgill shark (Hexanchus griseus), a bathypelagic species thought to have evolved approximately 200 million years ago, to better understand baseline genetic diversity and connectivity among populations. 124 samples from 11 collection sites across a global range were surveyed using seven mitochondrial genes totaling 3,978 base pairs and 11 species-specific microsatellite loci. Diversity was strikingly low across markers, to the point where relatively few were variable enough to be informative. Significant genetic structuring (global FST = 0.967, p ≤ 0.0001) indicates the presence of at least two widely divergent evolutionary lineages, one restricted to the Pacific Ocean and the other encompassing the entire Indo-Atlantic, with partitioning across two major biogeographic barriers to marine dispersal, the Malay Archipelago and the Isthmus of Panama. We hypothesize that several factors have shaped contemporary diversity and connectivity in H. griseus, among them (1) an overall slow rate of molecular evolution compared with other taxa, a result of lowered metabolism and/or the relative lack of selection pressure on deep-ocean animals; and (2) the interaction between thermotolerance and sea water temperature over the geo-evolutionary history of H. griseus.
DELL’APA, ANDREA; JOHNSON, JEFFREY; KIMMEL, DAVE; RULIFSON, ROGER. 2014.
East Carolina University, Greenville, NC, USA
A Social Network Analysis of the International Trade of Spiny Dogfish (Squalus acanthias): Fishery Management Aspects
The spiny dogfish (Squalus acanthias) is an important commercial shark species, with recent concerns over its conservation status. The major demand for its meat is from the European Union (EU) market, with the U.S. and Canada as its two major contributors. The U.S. has yet to support a spiny dogfish listing in the CITES Appendix II, although the U.S. Atlantic stock is under a fishery management plan (FMP) that proved to be successful in providing a certified sustainable fishery. We employed a cumulative sum technique to compare trade data for spiny dogfish export from U.S. and Canada to the EU in relation to the FMP adoption. We also constructed a social network to visualize changes in the European trade for spiny dogfish after adoption of the FMP and to predict future trade flow potentially affecting the conservation status of regional dogfish stocks in relation to recent management measures introduced in Europe. The social network analysis revealed that the exclusion of spiny dogfish from Appendix II will eventually affect the conservation status of dogfish stocks in Africa, Asia, South America, and the Mediterranean and Black Seas. Our results suggest that the species listing would provide an economic benefit for the U.S. Atlantic fishery, and will potentially foster the conservation status of other regional spiny dogfish stocks worldwide.
DI SANTO, VALENTINA. 2014.
Boston University, Boston, MA, USA
Ocean Acidification Exacerbates the Impacts of Global Warming on Embryonic Skates.
Rapid ocean acidification and warming have the potential to profoundly impact marine fauna and consequently, ecosystem dynamics and stability. Recent studies suggest that embryonic fish survival and fitness will be likely reduced by increasing acidification and temperature, however researchers should now focus on multi-stressor studies aimed to test the combined effect of these two climatic factors on fish physiology. In addition, local adaptation to thermal gradients may reduce the impact of global warming, but whether fish from different populations may respond differently remains unknown. Here I show the synergistic effects of acidification and warming on body condition, survival and aerobic scope of little skate (Leucoraja erinacea) embryos from two populations. Temperature had the strongest effect on development, survival and metabolic rates, but acidification further exacerbated stress on embryos. Thermal performance curves of populations exhibited countergradient variation and were affected differently by acidification. These findings emphasize the need for multi- stressor studies on different populations of fishes with wide geographic range to understand complex responses to climate change.
DRIGGERS, WILLIAM; FRAZER, BRYAN; ADAMS, DOUGLAS; ULRICH, GLEN; JONES, CHRISTIAN; HOFFMAYER, ERIC;CAMPBELL, MATTHEW. 2014.
(WD,CJ,EH,MC) NMFS Southeast Fisheries Science Center, Pascagoula, MS, USA; (BF,GU) South Carolina Dept. of Natural Resources, Charleston, SC, USA; (DA) Florida Fish and Wildlife Conservation Commission, Melbourne, FL, USA
Site Fidelity of Bonnetheads (Sphyrna tiburo) to Two Discrete Coastal Ecosystems in the Western North Atlantic Ocean
To examine the migratory patterns, habitat utilization and residency of bonnetheads (Sphyrna tiburo) in two separate estuarine systems within coastal South Carolina, tags were attached to 2,014 individuals from 1998-2012. In total, 190 bonnetheads were subsequently recaptured after 3-3,263 days at liberty, representing a recapture rate of approximately 9%. All bonnetheads were recaptured within the same estuary where originally tagged on intra and/or inter-annual scales, with the exception of six individuals, which were recaptured during migratory periods (i.e. late fall, winter and spring) in coastal waters off Florida, Georgia, North Carolina, and South Carolina. On 23 occasions groups ranging in size from 2-5 individuals were tagged together on the same day and location and subsequently recaptured together on the same date and location where initially tagged with times at liberty ranging from 12-1,329 days. Additionally, 17 individuals were recaptured multiple times with times at liberty ranging from 12-3,263 days; all individuals were recaptured in the same estuary where initially tagged. We hypothesize that bonnetheads are using South Carolina’s estuaries as summer feeding grounds due to the relatively high abundance of nutrient rich ovigerous blue crabs (Callinectes sapidus) during spring and summer months. The high degree of intra and inter-annual site fidelity demonstrated by bonnetheads in this region offers unique opportunities for in situ study of various aspects of the biology of chondrichthyan fishes, including identification of essential habitats, growth, homing mechanisms, mortality rates, movement patterns and social behavior.
DRYMON, J. MARCUS; AJEMAN, MATTHEW; POWERS, SEAN. 2014.
(JMD,SP) University of South Alabama, Dauphin Island, Alabama, USA; (MA) Harte Research Institute for Gulf of Mexico Studies, Texas A&M-Corpus Christi, Corpus Christi, Texas, USA
Dynamic Habitat Use of Young Bull Sharks Carcharhinus leucas in a Northern Gulf of Mexico Estuary
Understanding how animals alter habitat use in response to changing abiotic conditions is important for effective conservation management. For bull sharks (Carcharhinus leucas), habitat use has been widely examined in the eastern and western Gulf of Mexico; however, knowledge of their movements and the factors influencing them is lacking for populations in the more temperate north-central Gulf of Mexico. To examine how changes in hydrographic conditions affected the presence of young bull sharks in Mobile Bay, Alabama, thirty five sharks were fitted with internal acoustic transmitters and monitored through an acoustic telemetry array consisting of thirty four receivers between June 2009 and December 2010. Tagged sharks ranged in size from 60 to 114 cm fork length and were detected between the upper and lower portions of Mobile Bay. Our findings suggest a combination of hydrographic factors interact to influence the distribution of young bull sharks in Mobile Bay. The factors affecting the probability of detecting at least one bull shark varied both temporally (2009 vs 2010) and spatially (upper vs lower bay). Electivity analysis demonstrated that bull sharks showed highest affinity for warm water (29-32 °C), moderate salinities (10-11 psu) and normoxic waters (5-7 mg/l), although these patterns were not consistent between regions or across years. We suggest future studies coupling telemetry and hydrographic variables should, when possible, consider the interactions of multiple environmental parameters when defining the dynamic variables explaining the spatial distribution of the bull shark.
FONTENELLE, JOAO PEDRO; CARVALHO, MARCELO. 2014.
Universidade de São Paulo, Sao Paulo/SP, Brazil
Morphological Variation and Distribution of the Potamotrygon scobina Species Complex in the Amazon Basin (Chondrichthyes: Potamotrygonidae)
The species Potamotrygon scobina Garman, 1913, described from the lower Amazon River and recorded in many tributaries of the Amazon basin, has been reviewed and characterized based on its morphological characters and distribution. This widespread species has been subdivided into five separate species. Each species is diagnosed, described and compared to all species of Potamotrygon; their distribution is discussed in light of neotectonic transformations documented in the Amazonian region. Most of these species occur in specific rivers of the Amazon basin, providing relevant data for biogeographical studies. The documented morphological variation exemplifies how a thorough morphological approach is still a very important tool in systematics.
FONTANELLE, JOÃO PEDRO; LOBODA, THIAGO; CARVALHO, MARCELO. 2014.
Instituto de Biociências USP, São Paulo, SP, Brazil
Angular Cartilage Variation and Structure Among Neotropical Freshwater Stingrays (Chondrichthyes: Myliobatiformes: Potamotrygonidae)
A study of the morphological patterns of the angular cartilages of Neotropical freshwater stingrays has been undertaken in parallel to ongoing morphological and taxonomic revisions of this group. Data on the number, size and shape of these structures were gathered from radiographs, manual dissection, cleared and stained specimens, and dry skeletons of 24 of the currently recognized 28 species of the family. Potamotrygon species vary significantly in number (from one to three) and shape of the angulars, whereas Plesiotrygon presents a single, well formed element. Some specimens of Paratrygon aiereba present a single, reduced angular cartilage, but Heliotrygon lacks them entirely. Morphological patterns of the angular cartilages may help elucidate issues regarding the taxonomy, biogeography, origin and diversification of the family.
FORDHAM, SONJA. 2014.
Shark Advocates International, Washington, DC, USA
Conserving America’s Forgotten Shark: Management of Dusky Smoothhound (Mustelus canis) Fishing in the U.S. Atlantic
The dusky smoothhound (Mustelus canis), also known as the smooth dogfish, is the only U.S. Atlantic shark subject to targeted, unlimited fishing. Unlike most other commercially valuable elasmobranchs in the region, smoothhounds have not yet been evaluated in terms of population status or ecological risk. Landings more than doubled from 2000 to 2011, making smoothhounds one of the country’s most heavily fished sharks. While smoothhounds are marketed locally in Mid-Atlantic states, international demand for meat (particularly fish and chips) reportedly drives fisheries. Fins are sent to Asia for use in shark fin soup. Specific information on exports is scarce due to the lack of federal regulation, which has been stalled due to the absence of sustainable catch recommendations, changes in lead management responsibility, and low public concern. Initial state catch limits were quickly revoked. Text in the federal Shark Conservation Act of 2010 suggesting smooth dogfish be exempted from tougher national shark finning prevention measures – although not yet interpreted into federal regulation — has led to weaker state finning bans and postponement of a federal precautionary landings cap. Exceptions for smoothhounds have also been included in several East coast state shark fin bans, without justification. Long-term sustainable fishing for this relatively prolific shark depends on prompt evaluation and regulation of exploitation, while harmonization of shark conservation standards would benefit national, regional, and international elasmobranch policy development. Scientists, resource managers, elected officials, and concerned citizens all have roles in achieving these goals.
GARDINER, JAYNE; WHITNEY, NICHOLAS; HUETER, ROBERT. 2014.
Mote Marine Laboratory, Sarasota, FL, USA
Smells Like Home: Olfactory Contributions to Homing Behavior in Blacktip Sharks
Homing is one of the most remarkable animal behaviors in the marine environment, as animals perform transoceanic migrations to return to their natal areas to reproduce. Marine navigation is believed to be guided by different sensory cues over different spatial scales. Geomagnetic cues are thought to guide long-range navigation, while visual or olfactory cues allow animals to pinpoint precise locations, but the complete behavioral sequence is not yet understood. Terra Ceia Bay (TCB) is a primary nursery area for blacktip sharks, Carcharhinus limbatus, on Florida’s Gulf coast. Young-of-the-year animals show strong fidelity to a specific home range in the northeast end of the bay and will rapidly return if displaced. Older juveniles demonstrate annual philopatry for the first few years: migrating as far south as Florida Bay each fall, then returning to TCB each spring. To examine the sensory cues used in homing, we captured neonate (< 3 weeks) blacktip sharks from within their home range, fitted them with acoustic tags, and translocated them to release sites 8km away in adjacent Tampa Bay. Intact animals returned to their home range, within 36 hours on average, and remained there. Animals with olfaction blocked also returned to their home range, within 130 hours on average, but did not remain there. Instead, they moved throughout TCB and in and out of Tampa Bay. These results suggest that while other cues guide navigation over the long range, olfactory cues are used over the short range, allowing the animals to recognize their specific home ranges.
GELSLEICHTER, JIM; GRUBBS, R. DEAN; POULAKIS, GREGG; CARLSON, JOHN; ANDERSON, BRENDA; GULAK, SIMON. 2014.
(JG,BA) University of North Florida, Jacksonville, FL, USA; (RDG) Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA; (GP) Florida Fish and Wildlife Conservation Comission Charlotte Harbor Field Laboratory, Port Charlotte, FL, USA; (JC,SG) NOAA Fisheries Panama City Laboratory, Panama City, FL, USA
Hermaphroditism and Other Aspects of Reproduction in the Endangered Smalltooth Sawfish (Pristis pectinata)
Because of its status as the only domestic U.S. marine fish currently listed as endangered under the U.S. Endangered Species Act (ESA), it is rare to have opportunities to necropsy specimens of the smalltooth sawfish (Pristis pectinata), a limitation that complicates efforts to obtain much-needed information on the reproductive biology of this poorly studied species. Due to this, the present study used plasma concentrations of the gonadal sex hormones testosterone, progesterone, and 17β-estradiol along with opportunistic, post-mortem examination of specimens that have died unintentionally as a result of various natural or unnatural causes (e.g., cold stress, capture as bycatch in fisheries) to obtain preliminary data on the reproductive cycle of P. pectinata. Based on these observations, a seasonal reproductive cycle for this biennially reproducing species is proposed. In addition, based on necropsy data, it has been determined that male P. pectinata may normally exhibit a rudimentary form of hermaphroditism as all male sawfish examined to date have possessed ovaries in addition to testes and male genitalia.
GIRESI, MELISSA; PORTNOY, DAVID; GRUBBS, DEAN; SKOMAL, GREGORY; MCCANDLESS, CAMI; FRAZER, BRYAN; DRIGGERS, WILLIAM; RENSHAW, MARK; GOLD, JOHN. 2014.
(MG) Texas A&M University, College Station, TX, USA; (DP,JG) The Harte Institute, Corpus Christi, TX, USA; (DG) Florida State University, St. Teresa, FL, USA; (GS) Massachusetts Department of Marine Fisheries, New Bedford, MA, USA; (CM) NMFS Apex Predators Program, Narragansett, RI, USA; (WD) NOAA/NMFS, Pascagoula, MS, USA; (BF) South Carolina DNR, Charleston, SC, USA; (MR) Notre Dame, South Bend, IN, USA
Genetic Population Structure of the Dusky Smoothhound Shark, Mustelus canis, in U.S. Waters
The dusky smoothhound shark, Mustelus canis, is listed as a Species of Concern under the Highly Migratory Species (HMS) fisheries management plan. The National Oceanographic and Atmospheric Association (NOAA) recognized the need for baseline data on stock structure of M. canis in U.S. waters. Elucidating patterns of genetic diversity and assessing genetic divergence among localities is an essential first step to managing M. canis resources. In this study, we utilized sequences of mitochondrially- encoded NADH-2 and 18-nuclear encoded microsatellites to test the null hypothesis that M. canis in comprised of one genetically panmictic population in U.S. waters. Results of the genetic analyses reject the null hypothesis and suggest that there are genetically distinct stocks in U.S. waters. Comparisons among sequences of NADH-2 within and among geographic localities suggest that there may have been a recent a recent expansion of M. canis across the U.S. Atlantic and that the insular form (M. canis insularis) has diverged from the continental form. Initial analyses comparing multi-locus genotypes across geographic localities revealed that there are likely multiple genetically diverged stocks within the U.S. Atlantic (study ongoing). Results of this study will provide a baseline assessment of connectivity among geographic localities of M. canis, which will be useful in the upcoming stock assessments for this species.
DE AVECEDO, MELISSA GONZALES; GELSLEICHTER, JIM. 2014.
University of North Florida, Jacksonville, Florida, USA
Hormone Regulation of Sperm Storage in Female Bonnethead Sharks (Sphyrna tiburo)
Female sperm storage is a phenomenon that arises in many different taxa, allowing viable sperm to be retained in the reproductive tract for an extended time period. Previous studies have determined that reproductive hormones may play an important role in regulating various aspects of sperm storage in certain vertebrates, including the long-term survival of sperm and its release near the end of the storage period. However, to date, no published studies have investigated the hormone regulation of sperm storage in the reproductive tract of female elasmobranchs despite evidence for this phenomenon in several shark species. Therefore, the purpose of this study was to investigate if gonadal steroid hormones such as 17β-estradiol, androgens, and progesterone, may play a role in regulating this poorly understood process, which have been shown to increase in circulation during various periods of sperm storage. To accomplish this, circulating concentrations of gonadal sex hormones and the distribution of sex steroid receptors in the oviducal gland, the sperm storage organ of female sharks, were examined in the bonnethead shark (Sphyrna tiburo), an annually-reproducing species known to store sperm for a 3-6 month period between copulation and ovulation/fertilization. As demonstrated in previous studies, female bonnetheads exhibited increases in circulating steroid concentrations both during (testosterone, 17β-estradiol) as well as near the end (progesterone) of the sperm storage period. Immunocytochemical analysis of androgen, estrogen, and progesterone receptors in the oviducal gland demonstrated that epithelial cells of sperm-storage tubules and spermatozoa itself are direct targets for these hormones.
DE AVECEDO, MELISSA GONZALES; GELSLEICHTER, JIM; FRAZER, BRYAN; BELCHER, CAROLYN; ANDERSON, BRENDA. 2014.
(MGA,JG,BA) University of North Florida, Jacksonville, Florida, USA; (BF) Department of Natural Resources, Charleston, South Carolina, USA; (CB) Department of Natural Resources, Brunswick, Georgia, USA
Characterization of Reproduction in Bonnethead Sharks (Sphyrna tiburo) from the Southeastern U.S. Atlantic Coast
Bonnethead sharks (Sphyrna tiburo) are a component of the small coastal shark (SCS) fishery complex, and are caught regularly in recreational and commercial fisheries. Despite being well studied in the Gulf of Mexico, little is known about bonnetheads that reside on the U.S. Atlantic coast. The main goal of this study is to improve management of U.S. Atlantic bonnethead populations so they do not become overexploited. To contribute to this, my objective is to obtain critical information on reproductive biology of these populations. To accomplish this, male and female bonnetheads are being collected monthly through combined efforts of UNF, SCDNR, and GADNR along with commercial fishers from South Carolina and Florida waters. Reproduction stage is assessed using morphological, histological, and endocrinological analysis. Current data suggests that follicular development occurs in females between the months of January and early April followed by ovulation, which appears to take place in mid-to late April. Sperm storage appears to occur in the oviducal gland between late September to this same period based on histological analysis. Ova or pups were present in the uteri of mature females between late April to early September, suggesting that gestation is slightly greater than 4 months. Spermatogenesis in males appears to peak around late August/early September, based on testis morphology and histology. Further investigations use plasma sex steroid hormone concentrations throughout reproductive events to validate characterization of reproductive patterns. Resulting data will provide comparisons of reproductive cycles and seasonality between Atlantic and Gulf of Mexico bonnethead populations.
GRAHM, FIONA; HAMMERSCHLAG, NEIL; ESTEVANEX, MARIA. 2014.
University of Miami, Miami, FL, USA
Quantifying Habitat Protection for Shark Species in South Florida and The Bahamas Using Satellite Telemetry
Many species of large sharks are in decline, and the benefits offered by marine protected areas to these wide ranging marine predators is still unclear. Florida and The Bahamas is an ideal location to examine core areas of habitat use in relation to spatial management zones, as Florida has varying levels of jurisdiction and protection for sharks, while The Bahamas is a shark sanctuary and information on the efficacy of these protected areas for sharks is lacking. Satellite telemetry data for a total of 92 individuals within three highly mobile species, the great hammerhead (Sphyrna mokarran), tiger shark (Galeocerdo cuvier), and bull shark (Carcharhinus leucas), was examined, in order to evaluate the use of MPAs in both the south Florida and Bahamas regions. Core areas of use were identified, and the proportion of core use within each management zone was quantified. Results from 26 tagged bull sharks demonstrate that none of their core habitat is currently within areas that protect the species from fishing pressure, more specifically, prohibiting the landing of the species. Analysis of data from 22 tagged great hammerhead sharks illustrates that 17.88% of their core habitat is currently protected, and that 34.74% of tagged tiger shark (n=44) core habitat is within protected areas. The results from this study have valuable implications for marine conservation planning and help to develop an understanding of the current and potential level of protection for these top predator species.
GRUBBS, R. DEAN; COTTON, CHARLES; DALY-ENGEL, TOBY; KERSTETTERM DAVID. 2014.
(RDG,CC) Florida State University Coastal and Marine Lab, St. Teresa, Florida, USA; (TDE) University of West Florida, Pensacola, Florida, USA; (DK) Nova Southeastern University Oceanographic Center, Dania Beach, Florida, USA
Post-release Survival and Vertical Movements of Bluntnose Sixgill Sharks (Hexanchus griseus) in Four Oceanic Regions
The bluntnose sixgill shark (Hexanchus griseus) occurs worldwide in tropical and temperate seas typically at depths over 200 m associated with insular and continental slopes, seamounts and submarine canyons. We used modified longlines to capture bluntnose sixgill sharks in the Central Pacific Ocean (off Hawaii, N=26), in the Northwest Atlantic Ocean (off Virginia, N=4), in the northern Gulf of Mexico (off Florida, N=19) and in the Bahamas (Exuma Sound, N=8). Sharks 175-500 cm total length were captured 265-1,153 m deep. Twenty sixgill sharks were tagged with pop-off archival satellite transmitters (PSATs) to assess post-release survival and recovery time and to compare patterns of vertical movements between regions. Eighteen of 20 PSATs (90%) reported after 9 to 187 days at liberty (average retention was 87% of programmed time). Post-release survival was high (83%) but depth data suggest recovery from capture requires 48-60 hours. Mortality rates and recovery time did not differ significantly between sharks that were brought aboard the vessel and those that remained in the water during tagging. Bluntnose sixgill sharks displayed distinct diel vertical migrations in all regions, occurring shallower during night than during day. Vertical migrations were mediated by water temperature and migration depths reflected regional differences in thermoclines and perhaps light attenuation (turbidity/productivity). Average nighttime depths ranged from 175 m (Virginia) to 450 m (Exuma Sound) whereas daytime depths ranged from 300 m (Virginia) to 900 m (Exuma Sound). Nighttime and daytime temperatures were near 17°C and 5°C, respectively, across all regions.
GUTTRIDGE, TRISTAN; KESSEL, STEVEN; CHAPMAN, DEMIAN; HOWEY-JORDAN, LUCY; BOND, MARK; FINGER, JEAN-SEBASTIAN; BULLOCK, ROBERT; BROOKS, JILL; CASHMAN, RACHEAL; FLANAGAN, DAVID; GRUBER, SAMUEL.
(TG,JB,RC,DF,SG) Bimini Biological Field Station Foundation, South Bimini, Bahamas; (SK) Windsor University, Windsor, Canada; (DC,MB) Stony Brook University, New York, NY, USA; (LHJ) Microwave Telemetry, Columbia, MD, USA; (RB) Hull University, Hull, UK; (JSF) Humboldt Institute, Berlin, Germany
Movement Patterns and Habitat Use of the Great Hammerhead Shark, Sphynra mokarran in Bimini, Bahamas and Florida, USA
Sphynra mokarran is a bycatch species in a variety of fisheries throughout its range and population declines are suspected because of the high value of their fins in the international fin trade. Further management of this species is hindered by susceptibility to mortality during capture and lack of basic information about spatial and habitat use. Using a combination of satellite and acoustic telemetry we aim to assess the movement patterns and habitat use of endangered (IUCN) S. mokarran tagged in two ecologically dissimilar sites; 1) Bimini, The Bahamas and 2) Jupiter Inlet, Florida, USA. Since 2011, sharks have been tagged intermittently in Florida with 9 individuals (250-350cm) implanted with V16 acoustic transmitters. These sharks are tracked through an acoustic array data share consortium (http://www.theactnetwork.com/). Preliminary analysis indicates no post-tagging mortality and all individuals were detected throughout the array for > 12 months. Two individuals were detected ~300km north of Jupiter Inlet near Cape Canaveral, and 4 sharks were detected returning to the Jupiter area over two consecutive years during the winter months. During 2014 in Bimini, 17 sharks were externally fitted (via free-diving) with acoustic tags and a receiver array was established to monitor their local movements. Preliminary results from The Bahamas and the US suggest this species is migratory with evidence of seasonal site fidelity to local areas. The deployment of high-rate satellite tags will provide high-resolution vertical behavioral data to be combined with acoustic telemetry data for the purpose of providing spatial information critical for conservation management.
HART, HANNAH; GELSLEICHTER, JIM; AHEARN, GREG. 2014.
University of North Florida, Jacksonville, FL, USA
Transport of Di and Tripeptides in the Intestine of Sphyrna tiburo Many elasmobranchs are considered top predators with worldwide distribution, and in
general these fish play an important role in the transfer of energy from the lower to the upper trophic levels within the marine ecosystem. Despite this, with the exception of a few studies on glucose uptake in the shark gastrointestinal tract, the functional process of food absorption and digestion in elasmobranchs remains unclear. Given their carnivorous diet, the present study sought to expand knowledge on nutrient absorption in elasmobranchs by focusing on the uptake of products of protein metabolism. To accomplish this, the presence and function of Peptide transporter 1 (PEPT1), a protein found within the intestinal brush border membrane (BBM) of higher vertebrates that is responsible for the translocation and absorption of small peptides released during digestion by the luminal and membrane-bound proteases, was explored in the shark intestine, focusing on the bonnethead, Sphyrna tiburo. PEPT-1 was isolated and sequenced from S. tiburo scroll valve using molecular approaches and its presence and distribution in the gastrointestinal tract was explored using immunohistochemistry. Furthermore, BBM vesicles (BBMV) were isolated from S. tiburo intestine and used to investigate transmembrane transport properties and rates of 3H-glycylsarcosine uptake as a model dipeptide.
HARTOG, KYRA; HAMMERSCHLAG, NEIL; IRSCHICK, DUNCAN. 2014.
(KH,NH) University of Miami, Miami, FL, USA; (DI) University of Massachusetts at Amherst, Amherst, MA, USA
An Analysis of Shark Body Morphology with Respect to Trophic Level, Species, and Habitat Usage
Morphometric measurements can be used to answer questions regarding relationships between body dimensions and life history characteristics of various elasmobranch species. This study examines a series of measurements from 242 sharks of 8 species found in the waters of South Florida, the Florida Keys, and the Bahamas. These are compared to trophic level, species, and habitat usage in order to obtain a more complete picture of why species have certain body shapes. A series of 12 measurements are taken on sharks tagged through conservation research. These measurements are then analyzed both statistically and graphically with respect to existing data on trophic level, habitat usage, of each species in the study. An index of girth has been developed based on several of these measurements as well. Preliminary results show statistically significant differences in the various metrics between trophic levels as well as between species (t- test, independent; p < 0.01). Though the metrics for habitat use are not as definite as the specific number of trophic level or the clear definition between species, significance was also seen when morphometric measurements were compared by habitat type (t-test, independent; p <0.01). These results indicate that there may be a strong relationship between a shark’s physical and behavioral characteristics. It has not been determined, however, whether the physical aspects dictate behavior or vice versa. Further examination of shark body shape is needed as well as expansion to other species and other study sites, outside of the ones examined here.
HENDON, JILL; HOFFMAYER, ERIC; HIGGS, JEREMY; DRIGGERS, WILLIAM III; SULIKOWSKI, JAMES. 2014.
(HENDON, HIGGS) University of Southern Mississippi, Gulf Coast Research Lab, Ocean Springs, MS, USA; (EH,WD) National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA; (JS) Marine Science Department, University of New England, Biddeford, ME, USA
Reproductive Biology of the Blacknose Shark, Carcharhinus acronotus, in the Northern Gulf of Mexico
Analyses of reproductive data for blacknose sharks, Carcharhinus acronotus, collected off the east coast of the United States and the northern Gulf of Mexico (GOM) have shown variations in important reproductive variables. As the GOM study was conducted in a discrete region, the current study chose to examine blacknose sharks from the entire northern Gulf of Mexico to provide a more comprehensive estimate of the reproductive parameters associated with this population. Six hundred and seven blacknose sharks were captured by gillnet or longline in the northern Gulf from 2008 to 2013 (males: n = 347, 350 – 1076 mm fork length (LF); females: n = 260, 342 – 1120 mm LF). The size at 50% maturity was 800 and 822 mm LF for males and females, respectively. Male gonadosomatic index (IG) and testis dimensions reached maximum levels in May suggesting a peak in sperm production during that time. Female IG and maximum follicle diameters were highest in June, indicating time of ovulation. Embryos ranged in size from 42.1 mm stretched total length (LST) in August, to 467 mm LST in May, with an average brood size of 3.6 ± 0.09 embryos and a male to female ratio of 1:1.05. These data indicate mating occurs in July/August, and parturition occurs in May/June, yielding an 11 month gestation period and annual periodicity. All reproductive variables were similar to those found for the Atlantic population with the exception of periodicity.
HIGGS, JEREMY; HENDON, JILL; HOFFMAYER, ERIC; DRIGGERS, WILLIAM; SULIKOWSKI, JAMES; BETHEA, DANA. 2014.
(HIGGS) University of Southern Mississippi, Department of Coastal Sciences, Ocean Springs, MS, USA; (HENDON) University of Southern Mississippi, Gulf Coast Research Laboratory, Center for Fisheries Research and Development, Ocean Springs, MS, USA; (EH,WD) National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS, USA; (JS) University of New England, Department of Marine Sciences, Marine Science Education and Research Center, Biddeford, ME, USA; (DB) National Marine Fisheries, Southeast Fisheries Science Center, Panama City Laboratory, Panama City, FL, USA
Reproduction of the Finetooth Shark, Carcharhinus isodon, in the Northern Gulf of Mexico
Among sharks within the genus Carcharhinus, intraspecific variability in life history parameters is becoming well defined. While differences in growth rates and size/age at maturity could be expected to occur among conspecifics across broad clines, variations in reproductive characteristics are thought to be rare, especially within a discrete region. Finetooth sharks, Carcharhinus isodon, are reported to display biennial reproduction; however, from 2005 to 2007, 12 gravid female specimens from the Gulf of Mexico (GOM) region were examined and two were found to have large vitellogenic follicles, demonstrating they were capable of reproducing annually. The degree to which female finetooth sharks in the GOM are reproducing annually is presently unknown. The goal of this study was to investigate finetooth reproductive biology and determine the degree of variability in reproductive periodicity. A total of 1,490 finetooth sharks were collected from 2006 to 2013 in northern GOM coastal waters from Louisiana to Florida (females: n = 834, 387 to 1384 mm fork length (FL); males: n = 656, 350 to 1321 mm FL). General biological parameters (fork length, weight, liver weight) and reproductive parameters (female: ovarian follicle size/state, oviducal gland width, uterus width, and for mature individuals gravid vs non-gravid; male: testis width/ length, epididymis width) were recorded from each individual. This study shows the mating period taking place during April/May, with parturition occurring in April/May/June, resulting in 11-12 month gestation period. Results also indicate that the GOM population of finetooth is exhibiting a mix of annual and biennial reproductive periodicity.
IMHOFF, JOHANNA; MICKLE, ALEJANDRA; PETERSON, CHESTON; GRUBBS, R. DEAN. 2014.
Florida State University, Tallahassee, FL, USA
The Effects of Sample Processing Methods on Light Stable Isotope and Mercury Analyses of Fish Muscle
When using fish white muscle samples for trophic and mercury contamination studies, it is important to consider the effects of sample processing protocols on δ13C and δ15N values. This is particularly true for elasmobranch fishes which retain isotopically light nitrogenous wastes, including urea, in their muscles, confounding δ15N results and their interpretation. While lipid extraction can remove some nitrogenous wastes from elasmobranch muscle, an additional water rinse step may be necessary to thoroughly extract urea. The objective of this study was to investigate the effects of lipid and urea extraction on stable carbon and nitrogen isotope ratios and mercury concentrations in fishes caught in coastal and deepwater longline surveys in the northern Gulf of Mexico. The effect of lipid and urea extraction was determined for coastal (Rhizoprionodon terraenovae) and deepwater (Centrophorus sp.) elasmobranchs, and the effect of lipid extraction was determined for coastal (Ariopsis felis) and deepwater teleosts (Urophycis cirrata). Lipids were extracted using a chloroform-methanol solution and urea was extracted by rinsing tissue with DI water. Results of this study will be used to determine appropriate tissue processing methods for elasmobranch and teleost fishes, determine if muscle can be processed the same way for both coastal and deepwater fishes, and determine if bulk muscle can be processed once for both stable isotope and mercury analyses.
KACEV, DOVI; HYDE, JOHN; BOHONAK, ANDREW J.; VETTER, RUSS; LEWISON, REBECCA. 2014.
(DK,AJB,RL) San Diego State University, San Diego, California, USA; (JH,RV) Southwest Fisheries Science Center, La Jolla, California, USA
Combining Genetics and Tagging Data to Test for Sex Biased Dispersal in Shortfin Mako Sharks (Isurus oxyrinchus)
Mako sharks are highly migratory predators that are caught in recreational, commercial, and artisanal fisheries throughout the Pacific. Understanding their population structure is vital for designing efficient management for the species. Previous mitochondrial DNA studies have shown that the equator acts as a barrier to gene flow in the Pacific. Here we use 13 microsatellite loci to test for nuclear genetic population structure in mako sharks across the Pacific Basin. Samples were collected from California, Taiwan, Australia, New Zealand, and Chile. Unlike the previous mitochondrial studies, our results do not show statistical population differentiation. We then compared the genetic structure to conventional tag data to test if male mediated dispersal explains differences in genetic patterns between nuclear and mitochondrial markers. We also tested to see if genetic patterns could be explained by ocean bathymetry. Analysis of conventional tag data suggests that males are more likely to disperse long distances, which could explain the difference between our results and those from previous mitochondrial studies.
KNOTTEK, RYAN; RUDDERS, DAVID; MANDELMAN, JOHN; SULIKOWSKI, JAMES; BENOIT, HUGUES. 2014.
(RK,JS) University of New England, Biddeford, Maine, USA; (DR) Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia, USA; (JM) John H. Prescott Marine Laboratory, New England Aquarium, Boston, Massachusetts, USA; (HB) Gulf Fisheries Centre, Fisheries and Oceans Canada, Moncton, New Brunswick, Canada
The Survival of Rajids Discarded in the New England Scallop Dredge Fisheries
Due primarily to regulatory factors, skates (family Rajidae) account for nearly half the total bycatch discarded during commercial fishing operations in the U.S. portion of the Northwest Atlantic Ocean. Although the New England scallop dredge fishery has the second highest skate discard rate, no information regarding their resiliency to interaction with this gear type exists. To gain insight into species-specific mortality rates, 295 tows were conducted across six research trips (2012-2013 fishing season), with a total of 4020 skates (little, Leucoraja erinacea, winter, Leucoraja ocellata, and barndoor, Dipturus laevis) evaluated and scored on vitality (i.e. reflex impairment) and condition (i.e. overt physical trauma) indexes. To quantify mortality rates associated with these indexes, 290 skates were maintained in a novel on-deck refrigerated flow-through seawater system for 72-hours. This study also assessed the effect of fishing conditions and practices on post-release mortality. Preliminary data based on condition and vitality indexes, suggests species-specific differences in post-release mortality exist. For example, highest mortality (up to 100%) was observed in barndoor skates while winter skates were most resilient (up to 23.5%). As such, a species-specific management plan may be more appropriate for skates in this fishery. A more extensive analysis of the data is underway.
KOLMANN, MATTHEW. 2014.
University of Toronto, Toronto, Canada
Functional Anatomy of the Ocellated Freshwater Stingray, Potamotrygon motoro
The evolution of the vertebrate head has a complicated history of functional reorganizations, exhibiting morphological patterns of both modularity and decoupling among musculoskeletal units. The evolution of jaws and hyoid suspensorium from branchial arches, and the resulting variations of these structures in major clades of vertebrates is a notable example. Although the gill arch to jaw transition is a well accepted theory regarding gnathostome evolution, more direct examination of how this repurposing of the arches has affected cranial muscle physiology and function has been overlooked. To this end, I examined patterns of conservation in how physiological and morphological characteristics contributing to muscle function have changed between the gill arches, jaws and hyoid suspension in the ocellated freshwater stingray, Potamotrygon motoro. Based on prior comparative anatomy and behavioral research, we hypothesize that aspects of muscle fiber physiology will be most divergent between jaws and branchial musculature, with hyoid muscle function showing an intermediate condition. We also hypothesize that hypaxial muscle function is a strong covariate with suction feeding performance, as evidenced by studies of other fishes. As a necessary first step, we describe the cranial anatomy of this taxon with a focus on functional morphological characters. We find that Potamotrygon, like other stingrays, exhibits a highly mobile hyoid apparatus, allowing for rapid jaw protrusion. We also present preliminary data on behavioral trials examining the putative muscle groups driving suction performance in this taxon, as well as characterization of contractile muscle physiology across cranial muscles integral to certain feeding behaviors.
LAUNER, ANDREA; STARR, RICHARD; EBERT, DAVID. 2014.
(AL) Moss Landing Marine Labs, Moss Landing, CA, USA; (SR) California Sea Grant Extension Program, San Diego, CA, USA; (DE) Pacific Shark Research Center, Moss Landing, CA, USA
Sex-specific Differences in Residency and Movement of Leopard Sharks (Triakis semifasciata) in a California Estuary
Estuaries are ecologically important interfaces of marine, freshwater, and terrestrial habitats which contain high habitat heterogeneity, making them important habitats for many resident and migrant species. Many shark species are seasonally abundant in estuaries, utilizing the habitat for reproduction and as nurseries. Habitats in estuaries are susceptible to alteration from anthropogenic and environmental effects such as global climate change, agricultural runoff, and dredging activities. These changes may have different impacts on groups within a shark population because sex-specific segregations are common for many shark species including Leopard Sharks (Triakis semifasciata). Movements of Leopard Sharks (n=17) were recorded using acoustic receivers (n=9) moored in Elkhorn Slough, CA, an important coastal estuary for Leopard Sharks, from March to September 2013. Residency was assessed by individual shark and compared by sex. Using proportion of detections per region of Elkhorn Slough, similarity of movement was compared using a Bray Curtis similarity plot. These data will be used to determine differential habitat use of Leopard Sharks within estuarine habitats and will help to predict how the population will be affected by future habitat changes.
LEARY, ARIANNE; GELSLEICHTER, JIM; GRUBBS, DEAN. 2014.
(AL,JG) University of North Florida, Jacksonville, FL, USA; (DG) Florida State Marine and Coastal Lab, St. Teresa, FL, USA
Oil Related Biomarkers in Centrophorus and Squalus Species in the years following the Deepwater Horizon Oil Spill
The Deepwater Horizon Oil Spill released nearly 50 million barrels of liquid petroleum into the Gulf of Mexico. This was the largest oil spill in U.S. history. At depth of about 1,500 meters, this spill created a unique yet challenging research opportunity. It is vital to determine the effects on Gulf wildlife from oil-related pollutants, particularly the polycyclic aromatic hydrocarbons (PAHs), which are the most toxic components of oil. Due to the rapid metabolism of these compounds, a variety of PAH biomarkers have been used to evaluate health effects from the oil spill, such as detoxification enzymes and biliary metabolites. Deep sea sharks, primarily Squalus and Centrophorus species, were collected from 2011-2013. Animals were evaluated for PAH biomarkers, specifically cytochromeP4501a1 and gultathione-S-transferase in the liver as well as PAH metabolites in the bile. Thus far the results suggests that species residing closer to Deepwater Horizon spill site show continuous exposure, whereas species that reside further away show exposure followed by recovery.
LEARY, ARIANNE; GELSLEICHTER, JIM; GRUBBS, DEAN. 2014.
(AL,JG) University of North Florida, Jacksonville, FL, USA; (DG) Florida State Marine and Coastal Lab, St. Teresa, USA
The Deepwater Horizon Oil Spill Impacts on Deep Sea Gulf Fishes
The Deepwater Horizon Oil Spill (DWH) was the largest oil spill in United States’ history, releasing nearly 50 million barrels of oil into the Gulf of Mexico. This incident occurred at about 1,500 meters providing a unique yet challenging research opportunity. The DWH affected an ecosystem that was not well known due to the many difficulties of deep sea research. Among many pollutants in oil, polycyclic aromatic hydrocarbons (PAHs) are of major concern due to their toxicity and carcinogenic characteristics. PAHs are quickly metabolized; therefore biomarkers of exposure are typically used to assess effects Liver enzymes that break down PAHs and biliary PAH metabolites have been frequently used to examine oil exposure. PAHs are lipophilic, hence associating with sediment, increasing exposure risks for bottom dwelling organisms. Therefore the purpose of this study was to characterize PAH biomarkers in resident, demersal teleost species such as the tilefish Lopholatilus chamaeleonticeps, and the hakes Urophycis cirrata and Urophycis floridana. Specifically liver enzymes and biliary PAH metabolites were examined. The trends for each species in regards to time since the occurrence of DWH as well as distance from the origin of the spill will be discussed.
LEWIS, JUSTIN; PATTERSON, WILLIAM III; MCLACHLIN, KATHERINE; CARLSON, JOHN. 2014.
(JL,WP) Department of Marine Sciences, University of South Alabama, Mobile, Alabama, USA; (KM) Electro Scientific Industries, Bozeman, Montana, USA; (JC) National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City, Florida, USA
Distinguishing Blacktip Shark, Carcharhinus limbatus, Nursery Areas in the Northern Gulf of Mexico with Vertebral Chemical Signatures
Understanding connectivity between juvenile and adult populations is critical for the conservation of exploited and non-exploited species. The analysis of trace metals incorporated into calcified structures of bony fishes (e.g., otoliths) has emerged as a powerful tool for estimating the proportion of adults derived from specific nursery areas. For coastal elasmobranchs, it may be possible to infer natal origin based on nursery-specific biogeochemical signatures in their vertebrae. To assess the efficacy of this approach, we collected neonate and young of the year blacktip sharks, Carcharhinus limbatus, (n = 41) from three regions (Florida, Alabama/Mississippi, and Texas) in fall 2012 and analyzed their vertebral centra with laser ablation-inductively coupled plasma- mass spectrometry (LA-ICP-MS). Three parallel ablation transects were assayed to construct trace metal maps and estimate nursery-specific biogeochemical signatures. Of the ten elements assayed, Ba, Ca, Cu, Mg, Mn, and Sr were consistently above detection limits. Maps of trace metal concentrations indicate Mn concentrations peaked and Sr concentrations dropped following birth. Biogeochemical signatures (element:Ca ratios) were significantly different among regions (Pillai’s Trace = 1.032, p <0.001), and quadratic discriminant function analysis yielded a mean regional classification accuracy of 69.3%. Texas had the lowest classification accuracy (54%); however, ablating greater vertebrae mass may increase the number of elements above detection limits, thus increasing discriminatory power. This is the focus of ongoing research, along with examining interannual variability in nursery signatures.
LUER, CARL; WALSH, CATHY; WYFFELS, JENNIFER; EDSBERG, LAURA. 2014.
(CL,CW) Mote Marine Laboratory, Sarasota, FL 34236, USA; (JW,LE) Daemen College, Center for Wound Healing Research, Amherst, NY 14226, USA
Experimental Wounding of Atlantic Stingrays, Dasyatis sabina: Correlating Gross Physical Changes with Wound Bed Histology in the Healing Response
Anecdotal reports of relatively rapid and infection-free healing of wounds in sharks and rays are common, yet controlled experimental wounding studies to characterize the healing process are rare. In ongoing studies to identify mucus-associated antimicrobial compounds and their potential role in the infection-free healing of wounds, experimental wounds were inflicted on pectoral fins of Atlantic stingrays, Dasyatis sabina, by excising the epidermal and dermal layers of skin and exposing the epaxial musculature. A reproducible timetable of gross physical changes in the wound bed during the healing process has been established. Following the initial formation and breakdown of superficial clotted blood (day 0-7), the bed appears to be covered by a thin layer of connective tissue (day 10-17), with the emergence after 20-22 days of a central raised area that gradually flattens and spreads to the wound margin by day 28, with uniform healing by 6-8 weeks. Histology of biopsied wound beds reveals that the restructuring of epidermal and dermal layers occurs much earlier than expected. Wounds biopsied over the range of 2 to 28 days indicate that the day 2 wound bed is covered already with a thin epidermis containing mucus cells and a clearly identifiable basal layer. Wounds biopsied at 8, 16, and 24 hours confirm that migration of epidermal cells from the wound margin onto the bed is well underway by 24 hours. The raised area at 3 weeks is associated with epidermal and dermal restructuring events.
LYONS, KADY; LAVADO, RAMON; SCHLENK, DANIEL; LOWE, CHRISTOPHER G.. 2014.
(KL,CGL) California State University Long Beach, Long Beach, California, USA; (RL,DS) University of California Riverside, Riverside, California, USA
Bioaccumulation of Organochlorine Contaminants and Response to Exposure in Male and Female Round Stingrays (Urobatis halleri) from Southern California
While contaminant concentrations have been reported for elasmobranchs around the world, none have examined bioaccumulation patterns across male and female age classes. The round stingray (Urobatis halleri) is a local benthic species that forages near areas of high organochlorine contamination and represents a good elasmobranch model. PCBs, DDT, and chlordanes were measured in juvenile and adult male and female stingrays from areas in southern California and a nearby offshore island, Santa Catalina. After maturity, summed contaminant concentrations significantly increased with size for adult males and females. Male and female stingrays collected from Santa Catalina Island had significantly lower concentrations that were approximately five times less than mainland animals. Potential toxicity effects mediated through activation of the Aryl-hydrocarbon receptor were explored through ethoxyresorufin-O-deethylase (EROD) activity assays. Mainland male stingrays exhibited significantly greater EROD activities than Catalina males while female stingrays from both locations were comparable and lower than mainland males. Our results suggest that PCBs and/or other structurally-related contaminants may be inducing a biological response in mainland males but not females possibly due to a dampening effect of estradiol; however, exact physiological repercussions of exposure remain to be determined. MACDONALD, CATHERINE. 2014.
University of Miami, Coral Gables, Florida, USA
Risky Business: Shark Conservation and Limits on the Potential Global Expansion of Shark Tourism
In recent years, economic valuation, which assigns dollar values to specific aspects of environmental quality and function, has become a popular and influential justification among conservationists for protecting ecosystems and wildlife, including large predatory sharks. Although there are clear benefits to communicating about the “value” of the natural world in ways that are widely comprehensible to policy makers and the public, there are potentially significant limitations to shark tourism as a driver of conservation, including associated opportunity costs. These factors are likely to be significant in economic assessments of the value of potentially dangerous wildlife, particularly large predators. An analysis of published expenses related to shark control and “bather protection” measures worldwide suggests that the economics of shark tourism may not be as straightforward (or favorable to sharks) as previously imagined, while geographical mapping of many shark tourism sites in the developed and developing world indicate that shark tourism is likely to be excluded to increasingly marginal areas as developing countries generate broader tourism bases. Accordingly, this research also assesses potential implications for policy making and elasmobranch conservation and management.
MENDES, NATÁLIA, MENDONÇA, FERNANDO; CRUZ, VANESSA; ASHIKAGA, YULDI; PORTELA, PAULINO; CAMARGO, SÂMIA; BURGESS, GEORGE; COELHO, RUI; SANTOS, MIGUEL; OLIVIERA, CLAUDIO; FORESTI, FAUSTO. 2014.
(NM,VC,YA,CO,FF) Laboratório de Biologia e Genética de Peixes, Instituto de Biociências de Botucatu – UNESP, Botucatu, São Paulo, Brazil; (FM,SC) Laboratório de Genética Pesqueira e Conservação, Instituto do Mar – UNIFESP, Santos, São Paulo, Brazil; (PP) Laboratório de Genética, Faculdade de Veterinária da Universidade de Santiago de Compostela – USC, Lugo, Santiago de Compostela, Spain; (GB) Florida Program for Shark Research, Florida Museum of Natural History, Gainesville, Florida, USA; (RC) Centro de Ciências do Mar, Universidade do Algarve – UAlg, Faro, Algarve, Portugal; (MS) Instituto Português do Mar e Atmosfera – IPMA, Olhão, Algarve, Portugal
Development of Microsatellite Loci for the Sharks Galeocerdo cuvier and Carcharhinus acronotus Using Second Generation Sequencing
In the last three decades several shark species have suffered drastic population declines. Among these the tiger-shark (Galeocerdo cuvier) and the blacknose-shark (Carcharhinus acronotus), are species heavily affected by fishing and classified on the IUCN Red List as “Near Threatened”. However, reviews that enable sustainability and management remain inconsistent. In this respect, the present study aimed the development of microsatellite markers using Next Generation Sequence for G. cuvier and C. acronotus species. Thus, 70.000 sequences of G. cuvier and 54.000 of C. acronotus were analyzed. After the characterization of microsatellites regions and development of primers for loci amplification, redundancy analyses were performed to avoid non-specificity of these loci. Until this moment 30 primers for each species were synthesized. Amplification of microsatellite fragments has been tested and standardized to 20 primers for each species and these will be validated in population analyzes. This study will continue with the genotyping of microsatellite fragments for identification of polymorphic loci. The development of such markers will contribute to a better understanding of the populations of these species, enabling greater efficiency in the development of conservation plans on global scale.
MULL, CHRISTOPHER; YOPAK, KARA; DULVY, NICK. 2014.
(CM,ND) Simon Fraser University, Burnaby, BC, Canada; (KP) University of Western Australia, Crawley, WA, Australia
Placentation and the Evolution of Brain Size and Structure in Sharks, Skates, and Rays
Chondrichthyans mark the evolutionary emergence of the brain archetype common across nearly all vertebrates, which is comprised of five major brain regions. Patterns of brain organization are correlated with both phylogeny and ecology, which are suggestive of neurological specialization and cognitive differences among species. In mammals and chondrichthyans, reproductive mode significantly affects relative brain size, with increased maternal investment associated with larger relative brain size. In light of the connection between life history and brain size, the effect of reproduction on brain organization is investigated here. Variation in brain organization is correlated with both habitat and reproductive mode. The majority of variation is characterized by a trade-off between major components of the forebrain and hindbrain, specifically telencephalon and medulla, and correlates with both reproductive mode and habitat depth. Placental species have the largest telencephalons and are often found in reef habitats or are coastal/oceanic, and must navigate complex three-dimensional environments. Bathyal egg-laying or yolk-sac live-bearing species are characterized by a relatively large medulla, likely reflecting their reliance on mechanosensory and electrosensory input. While brain organization correlates with habitat, the influence of reproductive mode consistently explains more variance in brain size and structure. Life history is intimately linked to the diversity of brain sizes and structures, behaviors, sensory specializations, and ecological niches of chondrichthyans.
NEWTON, KYLE. 2014.
Florida Atlantic University, Boca Raton, FL, USA
Magnetic Field Perception, Learning and Memory in the Yellow Stingray, Urobatis jamaicensis
Sharks and rays are hypothesized to use geomagnetic cues to orient and navigate across the ocean, but magnetoreception is not well documented in elasmobranchs. Yellow stingrays (Urobatis jamaicensis) were held in a flow through seawater tank under a 12:12 hr light dark cycle and were fed daily. Rays were randomly introduced from each of the four cardinal directions into a circular arena without magnetic treatments or controls in order to determine any location preferences within the arena. Neodymium magnets and non-magnetic controls were coated in epoxy to prevent confounding galvanic currents between the metal and seawater that would stimulate the electroreceptors. Training consisted of positive reinforcement with a morsel of food when the ray stopped over the location of a magnet previously buried in the sand, whereas incorrect choices were not reinforced. The learning criterion was the minimum latency for each ray to correctly orient and stop over a buried magnet (≥75%) in four tests per day for three consecutive days. Once criterion was met the training stopped and memory retention tests began without additional reinforcement. Each test was a simple choice between a magnet and a demagnetized control buried under the sand at a random location within the arena. Memory retention was tested four times per day every seven days for 12 weeks. All rays reached criterion within two weeks and retained the memory for over 60 days. Future experiments will increase the sample size of the current procedure and determine the mechanism of magnetoreception in elasmobranchs.
NOSAL, ANDREW; HASTINGS, PHILIP. 2014.
Scripps Institution of Oceanography, La Jolla, CA, USA
Shoreward Homing in Experimentally Displaced Leopard Sharks (Triakis semifasciata)
This study investigated shoreward homing in leopard sharks (Triakis semifasciata), displaced from a coastal aggregation site in La Jolla, California, USA to locations 9 km (n=8) and 18 km (n=9) offshore (depth=500-700 m). Sharks were tagged with continuous acoustic transmitters with depth and temperature sensors, released at the surface, and manually tracked for four (9-km displacement) or seven hours (18-km displacement). Given the inhospitable environment for this nearshore benthic species, the coastline was hypothesized to be the “goal” upon release. Swimming speed averaged 0.63±0.07 m/s (0.43±0.05 BL/s) and swimming depth averaged 21.4±5.1 m (maximum: 97.8 m). Seven of eight sharks displaced to 9 km advanced 5.4-8.4 km toward shore along fairly straight paths (linearity index, LI: 0.709-0.871). The one apparently disoriented shark swam 2.1 km offshore along a tortuous route (LI: 0.557). In contrast, five of nine sharks displaced to 18 km advanced 10.9-16.0 km toward shore along fairly straight paths (LI: 0.812- 0.921), whereas four appeared disoriented, swimming 15.2% slower and advancing only 1.1-3.1 km toward shore along tortuous paths (LI: 0.201-0.320). Consistent with improved shoreward homing by sharks released at the closer displacement site and “U- turns” made by oriented sharks that initially swam offshore, is the presence of some detectable, likely chemical, cross-shore gradient. One additional shark displaced to 9 km and released with its nostrils plugged appeared disoriented, swimming 1.2 km offshore along a tortuous route (LI: 0.203). Upcoming work will further investigate the importance of olfaction and other sensory cues, including magnetic and solar, to elasmobranch orientation and navigation.
O’BRYHIM, JASON; ADAMS, DOUGLAS; SPAET, JULIA; MILLS, GARY; LANCE, STACEY. 2014.
(JO) George Mason University, Fairfax, VA, USA; (GM,SL) Savannah River Ecology Laboratory, Aiken, SC, USA; (DA) Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, Melbourne, FL, USA; (JS) King Abdullah University of Science and Technology, Red Sea Research Center, Thuwal, Saudi Arabia
Relationships of Mercury Concentrations Across 23 Tissue Types for Three Shark Species
Mercury has been shown to cause reduced fertility, slower growth and developmental rates, abnormal behavior, and mortality in a variety of fish species, and also poses a human health risk. The ability of sharks to bioaccumulate high concentrations of mercury is well established. However, little is known regarding the distribution of mercury among different tissue types (e.g. muscle, fin, liver, kidney) within an individual. We evaluated total mercury concentrations from eight muscle regions, four fin types (2 regions per fin), and five organs from three different shark species (Carcharhinus falciformis, C. leucas, Sphyrna tiburo) to determine the relationships of mercury among tissue types and among species. Our goals included determining whether mercury concentrations of various tissue types could be predicted from a single fin-clip or muscle biopsy. Across species, total mercury concentrations were highest in the eight muscle regions (1.14 ± 0.31 to 3.1 ± 2.12 ppm dry wt) with significant correlations existing between each muscle region. Total mercury concentrations were lowest in samples taken from the center of the first dorsal, pectoral, and caudal (lower lobe) fins of all species (0.017 ± 0.008 to 0.055 ± 0.083 ppm dry wt). Mercury concentrations for these locations were highly correlated between each other and across species, as were samples taken from the trailing edge of the dorsal, pectoral, and caudal fins (upper and lower lobe). Our initial results suggest the potential for using non-lethal sampling to gain valuable information about the health of the animal and its ecosystem.
O’SHEA, OWEN; MANDLEMAN, JOHN; TALWAR, BRENDAN; BROOKS, EDWARD. 2014.
(OO,EB) Cape Eleuthera Institute, Eleuthera, Bahamas; (JM) John H. Prescott Marine Laboratory, New England Aquarium, Boston, MA, USA; (BT) Florida State University Coastal and Marine Laboratory, Teresa, FL, USA
Hierarchical Predation Behaviour in Four Species of Marine Apex Predator: Does Size Matter?
Assessing dominance between and among individuals is a fundamental prerequisite in establishing the boundaries of social structures and hierarchies within populations. While the concept of dominance is valuable when describing hierarchical relationships in natural systems, few data are available on heterospecific interactions, particularly in elasmobranchs. Here we provide empirical data from an opportunistic observation made from four sharks (Caracharhinus leucas, Galeocerdo cuvier, Sphyrna mokarran
and Carcharhinus perezi) competing for foraging opportunities on a fifth shark (C. perezi). Video data were analysed at one-second resolution and behaviours were coded into eight categories and durations were assessed. Behaviours during multiple species interactions were also assessed. Feeding opportunity within interactions among all sharks was dominated by G. cuvier (44% of time spent feeding, 15% spent guarding the resource) and to a lesser extent, C. leucas (11% of time spent feeding). Estimated sizes and length-mass conversions suggest G. cuvier to be the third largest individual, yet dominated interactions. Both G. cuvier and C. leucas defended the prey resource from the other two species, despite Sphyrna mokarran being the largest individual present. Interactions between the two competing species may have been mutually beneficial, with a greater cost on defending the resource rather than competing for it. While theoretical studies are effective tools when investigating dominance driven hierarchical interactions, empirical data are always more valuable. These observations are among the few to describe competitive interactions among heterospecific marine apex predators.
PETERSON, ASHLEY; PAIG-TRAN, MISTY; SUMMERS, ADAM. 2014.
(MP) CSU Fullerton, Fullerton, CA, USA; (AP,AS) U Washington, Friday Harbor, WA, USA
Mega Filtration: Using Biomimetic Models to Understand Manta Ray Feeding
Mobulid fishes (mantas and devil rays) filter prey smaller than the pore size of their filter pads. The branchial filter is formed from the five branchial arches; each arch presents both an anterior face directed at the incoming flow and a posterior face that is shielded from the incoming free stream. The flow through these filter elements is complex and varies with the angle and anatomy of the filter. We used enlarged 3D biomimetic models to examine fluid flow over a variation of filter morphologies and at different attack angles. Models were based on gross dissections of Manta birostris filter lobes and created with a 3D rapid prototyper. Fluid movement was visualized with a dye stream aimed to show flow in specific areas of the filter. In anterior and posterior orientations the fluid makes contact with the filter lobe and then makes a 90 degree turn into the filter pore. The vorticity of the system is complex and we distinguished three different processes that depend on orientation and fine scale morphology: 1) vorticity parallel to the plane of the filter that moves downstream, 2) vortices parallel to the free stream and perpendicular to the filter plane maintained in the pore opening, and 3) vorticity seen in anterior facing filter lobes with projections consisting of vortices shed downstream above the filter plane. This complicated vorticity indicates that some form of cyclonic filtration is playing an important role in the filter-feeding of Mobulids.
PETERSON, CHESTON; GRUBBS, DEAN. 2014.
(CP) Florida State University, Tallahassee, FL, USA; (DG) FSU Coastal and Marine Laboratory, St. Teresa, FL, USA
Community Structure and Stable Isotope Ecology of Sharks and Large Teleost Fishes in the Florida Big Bend
Community structure and trophic ecology of sharks and large teleost fishes in seagrass beds of the Florida Big Bend were investigated using fishery-independent longline and gillnet surveys and stable isotope analyses. Community structure was analyzed using a combination of cluster analysis, indicator species analysis, and non-metric multidimensional scaling (NMDS). Carbon and nitrogen stable isotope analyses were used to infer relative trophic structure of these taxa and the potential for regional variation in trophic patterns. We found community structure to be correlated with water clarity, salinity, and depth. Stable isotope analyses suggest this system is trophically diverse, with considerable isotopic overlap across many taxa. The results of our study suggest an ecological gradient in the Big Bend, culminating in a relatively distinct southern faunal zone; and we hypothesize patterns of community composition and trophic structure are related to varying levels of river influence across the habitat.
PFLEGER, MARIAH O.; GRUBBS, R. DEAN; DALY-ENGEL, TOBY S.. 2014.
(MOP, TSD) University of West Florida, Pensacola, FL, USA; (RDG) Florida State University, Tallahassee, FL, USA
DNA Barcoding in the Genus Squalus Reveals a Novel Dogfish Species from the Gulf of Mexico
Sharks of the genus Squalus are slow-growing, long-lived, and have long gestation periods, as is typical of most deep-water sharks. In addition, low genetic diversity is frequently observed, making this group slow to rebound from depletion due to overfishing. The shortspine spurdog shark (Squalus mitsukurii) is a putative circumglobal deep-water shark that was originally described from Japanese waters. This species is easily misidentified due to the high degree of similarity with their congeners, and recent taxonomic research from the Pacific has indicated that S. mitsukurii may in actuality comprise a species complex, a group of separate but closely related species. We analyzed 596 bp of the mitochondrial cytochrome oxidase 1 (CO1) gene (barcoding region) of Squalus cf. mitsukurii from the Gulf of Mexico and compared it to sharks from the type locality in Japan to test the hypothesis that Gulf S. mitsukurii comprise a distinct species. Our results show high bootstrap support for a 1.5-2.0% sequence divergence between Gulf of Mexico and Japanese S. mitsukurii, with 0.3-0.7% separation between Squalus cf. mitsukurii and S. cubensis, also from the Gulf of Mexico. Within-species divergence ranged from 0.0-0.5%. These results confirm that Squalus species in the Gulf of Mexico are more closely related to one another than they are to congener species in the Pacific regardless of nomenclature, and that Squalus cf mitsukurii from the Gulf of Mexico merits recognition as a novel dogfish species.
PORTNOY, DAVID; HOLLENBECK, CHRIS; GOLD, JOHN. 2014.
Texas A&M University – Corpus Christi, Corpus Christi, Texas, USA
Historical Genetic Demography and Stock Structure of the Blacknose Shark, Carcharhinus acronotus, in the western North Atlantic
Population structure and historical genetic demography of blacknose sharks, Carcharhinus acronotus, were assessed via variation in sequences of mitochondrial (mt)DNA and nuclear-encoded microsatellites. Samples came from the Gulf of Mexico (Gulf), the Florida Keys, the southeastern U.S. Atlantic (U.S. Atlantic), the Bahamas, and the Bay of Campeche (Mexico). Significant heterogeneity and/or inferred barriers to gene flow in microsatellites and/or mtDNA delineated three regional groups in U.S. waters: the U.S Atlantic, the eastern Gulf, and the western Gulf. The relationship of blacknose sharks from the Florida Keys to the Gulf and Atlantic was equivocal. Blacknose sharks from Mexico and the western Gulf are similar genetically, suggesting historical and/or current gene flow. On the other hand, blacknose sharks from the Bahamas appear relatively divergent and consequently isolated from all other sharks sampled. A minimum spanning network of mtDNA haplotypes and nested-clade analysis indicated population expansion in the Gulf and U.S. Atlantic, occurring less than 60 thousand years ago. The presence of shared haplotypes, common in the Bahamas but rare along the Florida Coast, suggests historical contact between these regions, while levels of genetic variation and estimates of long-term effective sizes indicate that the southern Gulf may have served as a refugium during the last glacial period.
PRICE, KIMBERLY; O’BRYHIM, JASON; SAUL, BRUCE; LANCE, STACEY. 2014.
(KP,BS) Georgia Regents University, Augusta, GA, USA; (JO) George Mason University, Fairfax, VA, USA; (SL) Savannah River Ecology Laboratory, Aiken, SC, USA
Diet Analysis of the Bonnethead Shark, Sphyrna tiburo, Around St. Catherine’s Island, Georgia
The trophic structure in the estuarine waters off the coast of Georgia is being altered due to reductions in larger predatory sharks and the resulting increase in populations of the mesoconsumer, Sphryna tiburo. This alteration may have important implications for the health of this ecosystem. However, in order to predict the effects of an increase in S. tiburo populations, it is important to identify its primary prey within this area of its range. We examined the stomach contents of 39 S. tiburo caught off the coast of St. Catherine’s Island, GA. Overall the diet of S. tiburo along the Georgia coast consisted primarily of crabs regardless of time of year, shark age, or shark gender. We did find some diet differences among sharks including that males consumed a higher amount of vertebrates than females, juvenile males consumed a greater amount of shrimp than adult males, and adult males were found to consume a greater amount of vertebrates than juvenile males. While crabs remained the primary prey item of S. tiburo throughout the year, a temporal analysis revealed a shift towards an increased consumption of other prey types (i.e shrimp, squid) during summer and fall months. This analysis will be instrumental in determining the ecological and economic effects of increasing populations of S. tiburo on lower trophic level species, as well as the overall estuarine habitat.
PROHASKA, BIANCA; TSANG, PAUL; DRIGGERS III, WILLIAM; HOFFMAYER, ERIC; WHEELER, CAROLYN; SULIKOWSKI, JAMES. 2014.
(BP) Florida State University, Tallahassee, FL, USA; (PT) University of New Hampshire, Durham, NH, USA; (WD,EH) National Marine Fisheries Service, Pascagoula, MS, USA; (CW,JS) University of New England, Biddeford, ME, USA
Effects of Delayed Phlebotomy on Plasma Steroid Hormone Concentrations in Elasmobranchs
Circulating concentrations of steroid hormones can be utilized as a method for determining reproductive maturity and reproductive cycling in elasmobranchs. It is unknown how long steroid hormones remain stable in elasmobranch blood following capture, and thus how quickly these samples should be collected for the results of subsequent steroid hormone analyses to be accurate. The objectives of this study were to determine if the sex steroid hormones progesterone, testosterone and estradiol would remain at stable concentrations in the blood of sharks that were captured and left out of water un-refrigerated for 24 hours. Blood samples were serially drawn from five initially live sharks over a period of 24 hours. This analysis was conducted in two species of elasmobranchs, Squalus acanthias and Rhizoprionodon terraenovae. Results suggest that plasma concentrations of testosterone and estradiol are relatively stable in R. terraenovae blood over 24-hours, while progesterone and testosterone are relatively stable over a 24- hour period in S. acanthias blood. Additionally, no significant changes in hematocrit were detected in either species over the 24-hour period. This research represents an extreme situation in which sharks were un-refrigerated, and suggests that even when subjected to these conditions steroid hormone concentrations and hematocrit remain relatively unchanged in the blood following capture for up to 24 hours.
SHIFFMAN, DAVID; HAMMERSCHLAG, NEIL. 2014.
University of Miami, Miami, FL, USA
Conservation and Management Policy Preferences of Elasmobranch Researchers
A growing body of research suggests that many species of elasmobranchs are threatened with extinction from overfishing, habitat loss, and other threats. There is increasing public interest in their conservation, and many conservation and management policy solutions have been suggested and debated. For this study, a survey was distributed to the members of the American Elasmobranch Society, the Oceania Chondrichthyan Society, and the European Elasmobranch Association. While many conservation organizations support total bans on shark fishing and the sale of shark products (“shark sanctuaries” and “shark fin bans,”) the overwhelming majority of survey respondents believe that policies designed to promote sustainable fisheries are preferable over banning fishing entirely. Shark sanctuaries and fin bans had the lowest support of any suggested conservation and management policy among elasmobranch researchers. Additionally, many elasmobranch researchers expressed concerns over misinformation shared by conservation organizations and the focus of these organizations on what researchers believe to be the wrong issues and the wrong solutions. This study is the first to quantify the conservation and management policy preferences of the world’s leading experts on elasmobranchs, and results show a conflict between the policies that the research community recommends and the policies that many conservation organizations are promoting.
SKOMAL, GREGORY; CHISHOLM, JOHN. 2014.
Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
Movements of White Sharks in the Western North Atlantic
Despite its well-established presence in the North Atlantic, the white shark, Carcharodon carcharias, is not considered an abundant species and efforts to study its life history and ecology have been hampered by the inability of researchers to predictably encounter these sharks. However, with the protection of marine mammals over the last 40 years, the western North Atlantic gray seal population has rebounded and white sharks are expanding their foraging strategies to include active predation on these animals in the nearshore waters of Cape Cod, MA. From 2009-2013, we tagged 39 white sharks in this region to examine fine- and broad-scale movements, habitat use, site fidelity, residency, and feeding behavior. The sharks, which ranged from 2.4-5.5m total length (mean = 4.0 m), were tagged with pop-up satellite tags, smart positioning satellite tags, passive acoustic transmitters, and/or conventional tags. To date, we have found that some white sharks exhibit seasonal site-fidelity to the coastal waters of Cape Cod, returning over multiple years. Broad-scale movements have varied from a relatively restricted coastal seasonal migratory pattern to deep diving behavior and expansive use of offshore regions from the Sargasso Sea to the Mid-Atlantic Ridge. As demonstrated elsewhere, white sharks in the North Atlantic appear to have a complex migratory pattern likely linked to reproductive biology.
SULIKOWSKI, JAMES; CARLSON, AMY; JORDAN, LANCE. 2014.
(JS,AC) University of New England, Biddeford, ME, USA; (LJ) Microwave Telemetry Inc, Columbia, MD, USA
The Little Shark that Could: The Amazing Travels of a Young of the Year Porbeagle Shark
The porbeagle (Lamna nasus) is a predatory, endothermic shark that typically inhabits the upper pelagic zone from the surface to 200 m deep. Conventional and satellite tagging data suggest this species is highly migratory, however; these studies also indicate that this shark predominantly inhabits coastal and shelf-break regions, where they can remain localized for prolonged periods of time. Furthermore, the available information regarding the spatial ecology of this species has focused on adults with little to no information available on young of the year (YOY) or juveniles. The only information to date, suggests mature females tagged off the Canadian coast migrate to give birth in deep water in the Sargasso Sea, where the pups are reported to then follow the Gulf Stream as they return north. In order to test the hypothesis that the returning YOY sharks were using the Gulf of Maine (GOM) as a nursery ground, a satellite tag was attached to a 88 cm TL female on October 8th, 2012. Geolocation data indicated this shark was not using the GOM as a nursery ground, but instead embarked on a 10,000 km round trip that took it up to Nova Scotia Canada, down to South America, past Panama, Cuba, into the Gulf of Mexico and back up the Atlantic coast into the Gulf of Maine where the tagged released 5km from where it was attached 365 days earlier. This incredible little shark also made consistent dives from the surface to 300m with the deepest dives reaching nearly 700m.
TURNER, ALEC J.; ETNOYER, PETER J.; ROSS, STEVE W.. 2014.
(AT) College of Charleston, Charleston, SC, USA; (PJE) NOAA Center for Coastal Environmental Health and Biomolecular Research, Charleston, SC, USA; (SWR) University of North Carolina at Wilmington, Wilmington, NC, USA
Oviposition Substrate Preference in Scyliorhinid Shark Species
Understanding habitat usage is key to managing long-lived, late maturing organisms such as chondrichthyans. Roughly 13% of all chondrichthyans belong to the family Scyliorhinidae, colloquially called catsharks. Despite their abundance and diversity, life history characteristics for many catsharks remain poorly understood. Initial observations suggest oviparous scyliorhinid sharks may have microhabitat substrate preference for oviposition on deep-sea corals. Video from remotely operated vehicle surveys in southern California and the Gulf of Mexico were used to quantify egg case abundance in situ on deep-sea substrates (coral, sponge, rock, or fishing gear). Mean water temperature at sites of egg case observations was 7.7 ± 2.4 oC in the Gulf of Mexico and 7.9 ± 0.7 oC in southern California, while mean depth was 586 ± 145 m and 298 ± 68 m respectively. There was a significant difference in egg case abundance on each substrate type (X2 = 46.91, d.f. = 3, p < 0.001) and the position on the substrate (top, middle, or bottom) (X2 = 56.28, d.f. = 2, p < 0.001), with both coral and the top of substrates preferred. This information, along with planned behavioral microcosms and molecular identification of collected egg cases, will provide insight into whether oviposition preference exists in oviparous elasmobranchs and may help determine the extent to which microhabitats contribute to the reproductive success of scyliorhinid sharks.
VAN HEES, KELLEY; EBERT, DAVID. 2014.
Moss Landing Marine Laboratories, Moss Landing, CA, USA
Maternal Offloading of Mercury in Two Coastal Elasmobranchs in Elkhorn Slough, CA
Maternal offloading in elasmobranchs is one pathway through which juveniles may accumulate mercury, a harmful contaminant. Although elasmobranchs accumulate and may transfer high levels of mercury, this pathway has not been well investigated. This study examines maternal offloading of mercury in two common coastal elasmobranch species: leopard sharks (Triakis semifasciata) and thornback rays (Platyrhinoidis triseriata). Elasmobranchs were collected in Elkhorn Slough, California, an important elasmobranch nursery area. Muscle tissue and liver samples were collected from adult males and females. Embryos, including yolk, and ova were collected from gravid females during early and late development. Leopard sharks are also being aged to determine whether age correlates better with mercury concentration than length, and how female age affects offloading. Samples are currently being analyzed with a Direct Mercury Analyzer (DMA) 80 for total mercury concentration. Leopard shark muscle tissue mercury concentrations increased linearly with length, ranging from 0.47 mg/g (ww) to 1.80 mg/g, with an average of 0.97 mg/g. Thornback rays had lower muscle tissue concentrations with an average of 0.32 mg/g. Comparing female and offspring tissues at two development phases may help determine the route and degree of transfer of mercury to offspring. Comparing male and female liver concentrations may help determine the extent females are able to reduce their mercury loads. This study may elucidate further the mechanisms of maternal offloading in coastal sharks and rays.
WETHERBEE, BRADLEY; SHIVJI, MAHMOOD; BYRNE, MICHAEL; HARVEY, GUY; FRANCIES, MALCOLM; DUFFY, CLINTON; LYON, WARWICK. 2014.
(BW) University of Rhode Island, Kingston, RI, USA; (MS,GH) Guy Harvey Research Institute, Nova Southeastern University, Fort Lauderdale, FL, USA; (MB) University of Georgia, Athens, GA, USA; (MF, WL)National Institute of Water and Atmospheric Research, Wellington, New Zealand; (CD) Department of Conservation, Aukland, New Zealand
Mako Migratory Movements … mmm
Mako sharks (Isurus oxyrinchus) are a highly migratory, circumglobal species that occurs as bycatch in many pelagic fisheries and is also targeted by recreational fishers as a game fish in a variety of locations. Lack of information about movements, migrations and population structure has led to uncertainty about the status of mako stocks in multiple locations and raised concern about sustainability of fisheries in which mako sharks occur. Understanding of movements of mako sharks will aid in identifying migratory pathways, habitat use, potential interactions with fisheries and will clarify management jurisdictions for this international species. Satellite tracking of mako sharks in three locations, off the US East Coast, the Yucatan Peninsula and New Zealand and application of state space models are revealing characteristics of searching and transiting behavior over long distances, correlation of areas searched with environmental conditions and variable patterns in each location.
WYFFELS, JENNIFER; KING, BENJAMIN; VINCENT, JAMES; CHEN, CHUMING; POLSON, SHAWN; WU, CATHY. 2014.
(JW,CC,SP,CW) University of Delaware, Newark, DE, USA; (BK) Mount Desert Island Biological Laboratory, Salisbury Cove, ME, USA; (JV) University of Vermont, Burlington, VT, USA
Transcriptome Sequencing, De novo Assembly, and Annotation of Three Chondrichthyan Fishes, Leucoraja erinacea, Scyliorhinus canicula, and Callorhinchus milii
The little skate genome project is an initiative that seeks to characterize the complete genome of the little skate, Leucoraja erinacea. The project includes whole transcriptome shotgun sequencing to characterize stage-specific gene expression and alternative gene isoforms that serve to guide genome annotation efforts. We have sequenced, assembled and annotated the embryonic transcriptome of the skate using three individual stage 29 embryos with paired-end high-throughput RNA sequencing and compared it to embryonic transcriptomes from a chimera (Callorhinchus milii) and a shark (Scyliorhinus canicula). De novo assemblies of Illumina sequence data were generated using Trinity software and subsequently annotated using the Trinotate pipeline. Assembly quality was evaluated using Core Eukaryotic Genes Mapping Approach (CEGMA) and resulted in 90.3-99.2% coverage. Annotation of the transcriptomes includes Gene Ontology categories, protein domains, and pathway and ortholog mapping. Skate, shark and chimera assemblies shared 64.6% (5,492/8,494) of orthologous gene groups as defined by OrthoDB (http://orthodb.org). Comparison of skate genes with other organisms showed 11,102 predicted orthologs are shared with humans and 8,699 are shared with lamprey (Petromyzon marinus). Biological findings include transcripts for ornithine-urea cycle enzymes in all three species at an embryonic stage that coincides temporally with eclosion. The immune system, at this point in time, does not express transcripts for cytokines IL-2, 5, and 7 whose role in more recently evolved vertebrates includes hematopoiesis and lymphocyte development. Further development of SkateBase (http://skatebase.org) includes the infrastructure necessary to disseminate these newly acquired and annotated sequences.
YOPAK, KARA; LISNEY, THOMAS; COLLIN, SHAUN. 2014.
(KP,SC) University of Western Australia, School of Animal Biology and the UWA Oceans Institute, Crawley, WA, Australia; (TL) Queen’s University, Department of Psychology, Kingston, ON, Canada
Wake Up and Smell the Evolution: Variation in Olfactory Bulb Size in Cartilaginous Fishes
Olfaction is a universal modality by which all animals sample chemical stimuli from their environment. In cartilaginous fishes, olfaction is critical for various survival tasks, including localizing prey, avoiding predators, and chemosensory communication with conspecifics. Little is known, however, about interspecific variation in olfactory capability in these fishes, or whether the relative importance of olfaction in relation to other sensory systems varies with regard to ecological factors. In this study, we have quantified interspecific variation in the size of the olfactory bulbs (OB), the region of the brain that receives the primary sensory projections from the olfactory nerve, in 58 species of cartilaginous fishes. Our results show that the OBs maintain a substantial level of allometric independence from the rest of the brain across this group and that variability in OB size is correlated with ecological niche. The relatively largest OBs were found in pelagic-coastal/oceanic sharks, especially migratory species such as Carcharodon carcharias and Galeocerdo cuvier. Deep-sea species also possess large OBs, suggesting a greater reliance on olfaction in habitats where vision may be compromised. In contrast, the smallest OBs were found in the majority of reef-associated species, including sharks from the family Carcharhinidae. These results suggest that there is great variability in the degree to which these fishes rely on olfactory cues. The OBs have been widely used as a neuroanatomical proxy for olfactory capability in vertebrates, and we speculate that differences in olfactory capabilities may be the result of functional rather than phylogenetic adaptations.