(AEA,FF,FM) Stanford University, California, USA
Changing abundances of white sharks (Carcharodon carcharias) in the Mediterranean Sea
A major challenge to shark conservation efforts is the lack of estimates of shark removal rates and abundances in the world’s oceans. White sharks (Carcharodon carcharias) are rare worldwide, but are important apex predators. Many hypotheses have been posed about the history of white sharks in the Mediterranean Sea, but because white sharks are observed infrequently, we must rely on historical and anecdotal data to understand patterns of white shark abundance. After an extensive bibliographical search we built a data set from existing scientific literature, which included catch records, museum catalogs, and historical reports from 1554 to the present. We combined and integrated these data with generalized linear models and their extensions to model the abundance of white sharks through time and space, controlling for factors affecting the probability of reporting a catch, and then standardized the data to obtain a reliable index of population abundance. We tested previous hypotheses that sought to understand spatial and temporal patterns of abundance and distribution of white shark in the Mediterranean Sea. This study is more comprehensive than previous attempts to explore the ecology of white sharks in the Mediterranean Sea. We found that the history of fishing exploitation, prey abundance, and seasonal environmental regimes were good predictors of white shark distribution. This study aims to elucidate the population structure of white sharks in the Mediterranean Sea and enable us to evaluate conservation efforts, estimate baseline abundance, and assess changes in the status of white sharks.
AJEMIAN, MATTHEW J.; NEER, JULIE A.. 2013.
(MJA) Texas A&M University, Harte Research Institute, Corpus Christi, TX, USA; (JAN)
SEDAR, North Charleston, SC, USA
A multi-decade review of durophagous stingray research: from eradication to conservation
Known for their large-scale migrations, surface schooling behaviors and impressive durophagy, the myliobatid and rhinopterid stingrays have long fascinated naturalists and researchers worldwide. However, studies of the biology and ecology of these animals have considerably lagged behind other groups of marine fishes, including sharks. The low commercial value of these animals has likely impeded the development of management measures despite recently increased exploitation of rays by artisanal fisheries and the rising number of kill tournaments targeting these animals in the USA. These culling programs developed due to the purported impact of some species (e.g., Rhinoptera bonasus) on commercial shellfish, yet a concrete understanding of the range of resources these animals exploit is severely lacking. Though life history data are not extensive for this group, the few studies of rhinopterid and myliobatid ray reproductive biology suggest some species have among the lowest fecundity of all marine vertebrates. Given this extremely low reproductive output, any eradication procedures could have rapid and devastating impacts on populations of durophagous rays, as already evidenced by artisanal fishing fleets. This symposium will review the current state of knowledge of durophagous stingray biology and ecology. In this process, we will highlight the potential importance of this group in marine ecosystems and provide timely life history data critically needed by managers to better sustain these species, many of which are experiencing heavy anthropogenic pressure around the world.
AJEMIAN, MATTHEW; POWERS, SEAN. 2013.
(MA) Harte Research Institute for Gulf of Mexico Studies, Texas A&M – Corpus Christi, Corpus Christi, TX, USA; (SP) Dauphin Island Sea Lab, Dauphin Island, AL, USA; (SP) University of South Alabama, Mobile, AL, USA
SPOT on at the largest of scales: use of towed-float satellite telemetry to track movements and migrations of myliobatid and rhinopterid stingrays
Despite a preponderance of studies using satellite telemetry to track the migratory behavior of marine megafauna, attempts to use this technology on batoids remain limited. Many researchers elect pop-up satellite archival tags (PSATs) for large-scale movement studies, yet PSATs are costly and rarely produce precise position estimates. Smart Positioning or Temperature (SPOT) transmitters allow for precise, multi-scale tracking of species that regularly use surface waters. To date, SPOTs have been predominantly used on sharks and a variety of air-breathing marine vertebrates, with only one application to a batoid ray. Given the epipelagic nature of myliobatid and rhinopterid stingrays, we examined the potential for Wildlife Computers towed-float SPOT tags to monitor large and meso-scale movements of two representative species: the cownose ray (Rhinoptera sp.; n = 15) and spotted eagle ray (Aetobatus narinari; n = 8). Over the course of the study we explored multiple techniques to tether SPOT tags to rays, including dart tags, tail sutures, and spiracular harnesses, all with varying levels of success. Tag retention ranged between 1 and an estimated 155 days with multiple cases of tag scavenging evident from recovered units. Despite these limitations, we report on several consistent outmigration patterns of cownose rays in the northern Gulf of Mexico and inshore-offshore movements of spotted eagle rays along the Bermuda platform. Reductions in tag size and improved tethering techniques would undoubtedly broaden the applicability of this technology to monitor habitat use of medium-bodied stingrays and other marine vertebrates.
ANDERSON, BRENDA; GELSLEICHTER, JIM; FRAZER, BRYAN; BELCHER, CAROLYN. 2013.
(BA,JG) University of North Florida, Jacksonville, FL, USA; (BF) South Carolina Department of Natural Resources, Columbia, SC, USA; (CB) Georgia Department of Natural Resources, Brunswick, GA, USA
Non-lethal Characterization of the Reproductive Cycle of the Blacknose Shark (Carcharhinus acronotus) Using Circulating Levels of Gonadal Steroid Hormones
Characterization of shark reproductive cycles has historically involved culling individuals to examine gonad morphology to determine reproductive status. This practice, while necessary at first, is counterproductive to the conservation of shark populations. Measuring plasma steroids to characterize reproductive cycles has been used extensively with elasmobranchs. Chemiluminescence immunoassays (CLIA) have been validated for use with bonnethead shark (Sphyrna tiburo) plasma and correlate with cycles derived from RIA-measured plasma steroid concentrations and gonad morphological assessments. In this study, we used both CLIA and RIA to examine plasma steroid (17β-estradiol and testosterone) concentrations in the blacknose shark (Carcharhinus acronotus) to characterize their reproductive cycle. Steroid concentrations were compared to morphological assessments of reproductive status from culled specimens. CLIA-derived measurements were generally higher than those measured using RIA. However, seasonal changes in CLIA-determined plasma concentrations were consistent with those determined using RIA. Males exhibited higher levels of testosterone, indicative of spermatogenesis, in May when peak testis width was observed. In females, 17β-estradiol concentrations measured using CLIA and RIA did not correlate well with maximum follicular development. Therefore, circulating steroid levels appear to be a reliable method for characterizing reproductive status in male blacknose but not females. This may be associated with significant variability in female reproductive modes exhibited by this species. This raises concern about the use of this approach as a non-lethal surrogate for animal dissection when the species in question does not exhibit a highly synchronized reproductive cycle, especially when follicular development and gestation may occur concurrently.
ASCHLIMAN, NEIL. 2013.
St. Ambrose University, Davenport, IA, USA
Evolution of the durophagous stingrays (Batoidea: Myliobatidae)
In the last few years, estimates of the patterns and timing of the evolution of the durophagous pelagic stingrays (Myliobatidae) have been improved through new comparative data from morphology, the fossil record and DNA sequences. These recent studies are here briefly reviewed and a conservative summary of myliobatid diversification and origins is presented. The interrelationships and morphological evolution of the durophagous stingrays are discussed, including the nature of mobulids as derived myliobatids. An exploration of myliobatid origins includes estimates of the timing of their diversification and an assessment of gymnurids as a possible sister group. Finally, alternative taxonomic schemes currently in use are evaluated and the validity of the genus Pteromylaeus Garman 1913 is called into question
ATEATER, KIMBERLY; BERNARD, ANDREA; HESTER, JENNIFER; FRANCIS, MALCOLM; GORE, MAUVIS; JONES, CATHERINE; NOBLE, LES; ORMOND, RUPERT; SKOMAL, GREGORY; SHIVJI, MAHMOOD. 2013.
(KA,AB,JH,MS) Save Our Seas Shark Center, Nova Southeastern University, Dania Beach, FL, USA; (MF) National Institute of Water and Atmospheric Research Ltd, Wellington, New Zealand; (MG,RO) Marine Conservation International, South Queensferry, UK; (CJ,LN) Institute of Biological & Environmental Sciences, University of Aberdeen, Aberdeen, UK; (GS) MA Marine Fisheries Shark Research Program, New Bedford, MA, USA
A mitogenomics view of the genetic status and population history of the basking shark, Cetorhinus maximus
The basking shark, Cetorhinus maximus, has historically been a target of fisheries exploitation, leading to well-documented declines in parts of its range. Little is known about the genetic status and population history of this CITES Appendix II listed species. Prior analysis of basking sharks based on a single, non-coding, mitochondrial locus (control region (CR); 1,085bp), has suggested an absence of population structure and very low levels of genetic diversity (π = 0.0013) globally. In the present study, we assessed population genetic parameters by completing the first whole mitochondrial genome (~16,669 bp) survey of basking sharks sampled from three widespread geographic regions: the western North Atlantic (n=10), the eastern North Atlantic (n=10) and western South Pacific (n=10). Concordant with CR locus findings, whole mitogenome analyses (despite 15X more sequence data) showed no evidence of population differentiation and even lower genetic diversity (π = 0.0005). However, comparative analyses of individual loci revealed unexpected evolutionary dynamics: the protein coding genes ATP8, CO2, and ND3 contained the highest nucleotide diversity, while commonly utilized loci for population genetic studies (CR, ND2 and Cytb) showed an order of magnitude lower diversity. Bayesian Skyline Plot analyses of mitogenomes indicated a largely stable effective population size with limited growth. Demographic tests for population expansion produced non-significant values. Whole mitogenome findings of exceptionally low genetic diversity and results from population demographic analyses are consistent with a hypothesis of a historical bottleneck with limited population expansion thereafter, adding to conservation concerns for this regionally Endangered (IUCN Red List) species.
BADE, LYNDELL M.; BALAKRISHNAN, CHRISTOPHER N.; MCRAE, SUSAN B.; LUZKOVICH, JOSEPH L.. 2013.
East Carolina University, Greenville, NC, USA
A Genetic Technique to Identify the Diet of Cownose Rays, Rhinoptera bonasus: Analysis of Shellfish Prey Items from North Carolina and Virginia
Cownose rays are blamed for consumption of commercially important species of shellfish on the East Coast. We tested this assumption by developing a molecular technique for species identification from cownose ray gut contents. Digestive tracts sampled from 32 rays in Pamlico Sound, NC and Chesapeake Bay, VA contained pieces of partially-digested tissue, sludge, and minute shell fragments which made visual identification to the species level nearly impossible. We sequenced the cytochrome oxidase subunit I (COI) for a variety of locally acquired bivalve species of commercial and ecological importance in NC and Chesapeake Bay: Atlantic bay scallop, Eastern oyster, Baltic macoma, cross-barred venus, hard, soft shell, and stout razor clams.
Sequences were then used to design unique species-specific primers for each bivalve species to amplify polymerase chain reaction (PCR) products. We designed primers such that PCR products were sufficiently different in size to be distinguishable from one another when resolved on an agarose gel. Based on the primer design, multiplexing of several species in one reaction was possible. Tests of sample types from digestive tracts revealed that cownose rays in Virginia ate stout razor clams and soft shell clams. There was no evidence of commercially important bivalves like oysters and bay scallops being consumed by the rays in this study. Further sampling over an extended period of time and at additional locations is required to confirm these results. Best practices of tissue manipulation and handling techniques will be discussed to help inform methodologies for forensic testing on marine species.
Cetacea, which are suspected prey of C. megalodon. We ask, does C. megalodon change body size through time, and does the body size change correlate with and mimic the change seen in marine mammals? We compared body size estimates of C. megalodon to a dataset of marine mammal body sizes through time. We find that C. megalodon increases in body size over time, and predict that it will correlate with the body size change in marine mammals.
BANGLEY, CHARLES; RULIFSON, ROGER. 2013.
Institute for Coastal Science and Policy, East Carolina University, Greenville, NC, USA
Gastric evacuation, feeding ration, and potential predatory impact of spiny dogfish (Squalus acanthias) in the Northwest Atlantic
Spiny dogfish (Squalus acanthias) have long been suspected of damaging more valuable fish stocks by directly consuming or outcompeting those species. Despite much research interest in the trophic dynamics of this shark, currently no estimate of its food ration requirements exists for the Northwest Atlantic population. To assess food requirements of dogfish on the U.S. east coast, adult spiny dogfish were captured in the vicinity of Atlantic Beach, NC and transported to the Carteret Community College aquaculture facility in Morehead City, NC. While kept in captivity, dogfish were allowed to feed voluntarily on pre-weighed portions of frozen fish. After a pre-determined digestion period, remaining food was recovered from the stomach using nonlethal stomach tube gastric lavage and weighed. Regression analysis was used to estimate gastric evacuation rate, and both linear and exponential models fit the data well (R2 > 0.6). Daily ration was determined using models for both linear and exponential evacuation curves, and incorporated the Diana (1979) model to account for intermittent feeding. Using daily ration estimates and the proportion of key prey species in the dogfish diet from previous studies, the predatory impact of spiny dogfish relative to prey stock biomass was estimated.
BARKER, AMANDA; NOSAL, ANDREW; BURTON, RON. 2013.
Scripps Institution of Oceanography, La Jolla, CA, USA
Genetic Structure of Leopard Shark Populations along the Pacific Coast of North America
The leopard shark (Triakis semifasciata) is a common nearshore benthic elasmobranch endemic to the Pacific coast of North America, from Washington, USA to Mazatlan, Mexico. Leopard sharks aggregate at specific coastal locations in the spring and summer, but little is known about leopard shark movement patterns once aggregations disperse. As a result, the extent of potential gene flow remains to be fully elucidated. While the leopard shark is not currently a threatened species, understanding gene flow throughout the species’ range may provide insight into the population structure of similar species. Five microsatellite markers were used to analyze the genetic population structure of T. semifasciata throughout much of its range. Fin clips were collected from five locations in California and one location in Mexico (total N= 339). Our data show significant structuring among several locations. Evidence of gene flow between Santa Catalina Island and mainland populations is consistent with acoustic tracking data showing that leopard sharks occasionally cross the deep-water channel between Santa Catalina Island and the mainland, a minimum distance of 32 km. This provides an interesting contrast to leopard sharks’ generally benthic lifestyle. We conclude that T. semifasciata does not form one panmictic population and significant population structure is present.
BASSOS-HULL, KIM; HUETER, ROBERT; HULL, PETER; DOUGHERTY, DEAN; WILKINSON, KRYSTAN; MORRIS, JOHN; SELLAS, ANNA. 2013.
(KB,RH,PH,DD,KW,JM) Mote Marine Laboratory, Sarasota, FL, USA; (AS) California Academy of Sciences, Center for Genomic Studies, San Francisco, CA, USA
Biology and Genetics of the Spotted Eagle Ray in the Eastern Gulf of Mexico
The spotted eagle ray, Aetobatus narinari, is IUCN listed as near-threatened with a decreasing population trend. This study began in July 2009 to gather information on biology and behavior of spotted eagle rays in the eastern Gulf of Mexico (southwest Florida coast). Between July 2009 and October 2012, 349 spotted eagle rays (148 females, 201 males) were captured, measured, sampled, tagged, photographed, and released. Five percent (18 rays) were recaptured anywhere from five to 984 days (avg. 224.2 days ± 263.5 SD) after initial capture. Disc width ranged from 41.4 cm to 203.0 cm (119.2 cm ± 37.9 SD) and females were, on average, slightly larger than males (females 121.283 cm ± 39.6, males 117.9 cm ± 36.5 SD). Aerial surveys documented a decline from 97 individuals per flight (2009) to 6 individuals per flight (2011). Genetic data from one mitochondrial DNA locus (cytochrome b) and 10 nuclear microsatellite markers were used to investigate genetic diversity and structure. Based on 136 individuals, results identified nine unique haplotypes and genetic diversity estimates comparable to those reported for other batoid species (h = 0.72, Ho = 0.70). Population structure analyses do not show evidence of significant differentiation suggesting spotted eagle rays off southwest Florida comprise one, homogeneous population. These apparent declines off southwest Florida, together with concerns about sustainability of Gulf fisheries for rays in Mexico and Cuba, call for further investigations into stock structure, abundance, and habitat use of spotted eagle rays throughout the Gulf of Mexico and Caribbean Sea.
BEDORE, CHIRSTINE; MCCOMB, D. MICHELLE; KAJIURA, STEPHEN. 2013.
(CB) Duke University, Durham, NC, USA; (MDM) Ocean Classrooms, Boulder, CO, USA; (SK) Florida Atlantic University, Boca Raton, FL, USA
Visual biology of cownose rays, Rhinoptera bonasus
Sensory systems are tuned to provide functionality for a species according to its ecological characteristics. Cownose rays are derived Myliobatid rays that display several morphological and behavioral characteristics that reflect their ecological niche and adaptations in their sensory capabilities. Strictly benthic basal Myliobatids, like yellow stingrays, have dorsally positioned eyes, which affords them a 360° visual field in the horizontal plane, but restricts the ventral visual field. In contrast, cownose rays have laterally positioned eyes and benefit from an expansion of the vertical visual field to 360°, while retaining a large horizontal visual field of 321°. The large visual fields likely aid in visual tracking of conspecifics while schooling, however, the ability to track schoolmates may be limited by low-light conditions in their turbid estuarine and coastal habitats. Although cownose rays have the same visual temporal resolution as the reef inhabiting yellow stingray when light is not limited, the cownose ray scotopic temporal resolution is faster than yellow stingrays. This suggests that cownose rays are adapted for dim-light conditions and can visually track objects when light is limited. Color sensitivity is also spectrally tuned to the turbid, green-dominated estuarine waters that they inhabit; cownose rays have two cone classes, with maximal sensitivity to short- wavelength and long-wavelength light, in addition to a green-sensitive rod. This combination of photoreceptors enhances contrast of objects against their dim background. This suite of sensory adaptations would enhance tracking of schoolmates and predators, intraspecific communication, and image formation of objects in a variable light environment.
BELLEGGIA, MAURO; FIGUEROA, DANIEL E.; MASSA, ANA; BREMEC; CLAUDIA. 2013.
(MB,AM) Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina; (CB) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina; (DEF) Laboratorio de Ictiología, FCEyN, Universidad Nacional de Mar del Plata (UNMdP), Mar del Plata, Argentina
Dentition and Tooth Replacement Rate of the Narrownose Smoothhound Shark Mustelus schmitti
The genus Mustelus is the most specious genus of the Family Triakidae comprising at least 31 species. The narrownose smoothhound shark Mustelus schmitti inhabits coastal waters from southern Brazil (27o S) to Patagonia Argentina (47o45 ́S). A total of 47 males and 56 females of M. schmitti were collected on scientific trawl surveys conducted by the The National Institute of Fisheries Research and Development (INIDEP) in Argentina during November 2007, November and December 2008. To carry out quantitative and qualitative analyses, dental laminas were extracted from the jaw cartilage and attached to onionskin paper for the dehydration treatment, maintaining their original jaw position. Tooth replacement rate was estimated following established methods used for fossil sharks based on the premise that tooth length within each row decreases from the lingual to the labial side of the jaw as a consequence of wear. Thus, the length difference between consecutive teeth in four representative rows should be proportional to the tooth replacement rate. Mustelus schmitti exhibits homodentition, where teeth are similar is shape or design, arranged in a semi-pavement like dentition. The dental formula was 47-63 / 50-63 for juveniles, and 50-77 / 50-69 for adult specimens. Teeth from the symphysial and adsymphysial rows showed higher wear and faster replacement rates than adcommissural and commissural rows. The estimated mean replacement rate was four days/series. Considering the dental formulae and replacement rate, M. schmitti replaces approximately 5350 teeth each year throughout their life time.
BERNARD, ANDREA; FELDHEIM, KEVIN; HEITHAUS, MICHAEL; WINTNER, SABINE; WETHERBEE, BRAD. 2013.
(AB) Save Our Seas Shark Center USA, Nova Southeastern University, Dania Beach, Florida, USA; (KF) Field Museum, Pritzker Laboratory for Molecular Systematics and Evolution, Chicago, Illinois, USA; MH) School of Environment and Society, Florida International University, Miami, Florida, USA; (SW) KwaZulu-Natal Sharks Board & Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa; (BW) Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island, USA
The evolutionary history of a coastal-pelagic species: the global phylogeography of the tiger shark (Galeocerdo cuvier)
The tiger shark is a globally distributed, highly mobile, dietary generalist predator that plays an important role in community structuring. The population dynamics of this fishery exploited apex predator remain enigmatic in most parts of its range. We investigated the global genetic population structure and phylogeography of tiger sharks utilizing a multi-locus approach [10 nuclear microsatellite loci (n = 389) and two mitochondrial loci: control region (mtCR) (1,068 bp; n = 349) and cytochrome oxidase I (642 bp; n = 152)]. With respect to population structure, western Atlantic and Indo- Pacific tiger sharks were found to be highly genetically differentiated using all three sets of genetic markers; however, intra-basin population structure appears to be much more complex. For instance, patterns of genetic isolation by distance were detected using mtCR in the western Atlantic, and microsatellite DNA in the Indo-Pacific. Investigation into the evolutionary history of the tiger shark using coalescent analyses of the mtCR suggest an Indo-Pacific center of origin for the tiger shark, followed by colonization into the western South Atlantic via South Africa during the Pleistocene. Interestingly, tiger sharks collected from the western South Atlantic possess a number of unique mtCR haplotypes, but also haplotypes occurring in both the western North Atlantic and the Indo-Pacific. Overall analyses (diversity- and coalescent-based) suggest that the western South Atlantic was likely an important historical connection that facilitated dispersal between basins, allowing the tiger shark to attain its contemporary global distribution.
BIGMAN, JENNIFER J.; EBERT, DAVID A.; BIZZARO, JOSEPH J.. 2013.
(BIGMAN,DAE) Pacific Shark Research Center–Moss Landing Marine Laboratories, Moss Landing, CA, USA; (BIZZARO) School of Aquatic and Fisheries Sciences–University of Washington, Seattle, WA, USA
North Pacific spiny dogfish (Squalus suckleyi) trophic ecology: using integrated gut content and stable isotope analysis to infer short and long term feeding trends
North Pacific spiny dogfish (Squalus suckleyi) are commercially and ecologically important predators that are abundantly distributed in North Pacific waters, and therefore may play an important role in regional marine ecosystems. Most historic research on this species has been focused on dogfish collected within the inland waters of Washington and British Columbia, but little is known about offshore populations. We used traditional gut content analysis (GCA) and stable isotope analysis (SIA) to elucidate the trophic ecology of dogfish from central California, U.S.A. GCA allows for quantification of prey items contained within the stomach of a single individual and reveals what actual species are consumed on a short-term basis. SIA uses elements as tracers (specifically carbon and nitrogen) to identify predator-prey relationships as well as trophic position, allowing for long-term diet information. SIA analysis can be used to complement gut content data via integrating both short and long term food habits, enhancing information known about the trophic role of a given species. Based on GCA, the most abundant and important prey taxa by number, weight, and the prey-specific index or relative importance were euphausiids, fishes, and cephalopods. Similarly, the most frequently occurring prey taxa were fishes, euphausiids, and cephalopods. In addition to diet composition, sources of dietary variability with respect to size, sex, depth, location, season, and year were investigated for GCA and SIA and will be presented.
BIGMAN, JENNIFER S.; FINNEY, BRUCE P.; HAMILTON, SCOTT L.; EBERT, DAVID A.. 2013.
(JB, DAE) Pacific Shark Research Center, Moss Landing Marine Laboratory, Moss Landing, CA, USA; (BPF) University of Idaho, Pocatello, ID, USA; (SLH) Moss Landing Marine Laboratories, Moss Landing, CA, USA
Monterey Bay food web: Insights from stable isotope analysis
Marine food webs are an essential component to developing and implementing ecosystem-based management plans. We used stable isotope analysis of carbon and nitrogen to assess trophic positions and sources of primary productivity for several species in Monterey Bay, in central California. This data was used to create trophic links among species from numerous trophic positions and habitats with emphasis on an apex predator, the North Pacific Spiny Dogfish, Squalus suckleyi, and its prey. The Bay is a dynamic upwelling ecosystem with many resident and seasonally abundant marine organisms that is part of the Monterey Bay National Marine Sanctuary, the largest in the network of marine sanctuaries that are federally protected. Due to the plethora of species in this area, trophic interactions are extremely important to quantify. Fishes, cephalopods, crustaceans, and chondricthyans were opportunistically collected in the Bay, and include Krill (Euphausiid spp.), Sand dabs (Citharichthys sordidus), Longspine thornyhead (Sebastolobus altivelis), Dover sole (Micostomus pacificus), shrimp (Pandalus spp., Crangon spp.), Anchovy (Engraulis mordax), Sardines (Sardinops sagax), Pacific herring (Clupea fallasi), English sole (Parophrys vetulus), Longspine combfish (Zaniolepis latipinnis), Plainfin midshipmen (Porichthys notatus), Croaker (Genyonemus lineatis), Market squid (Doryteuthis opalsecens) and North Pacific spiny dogfish (Squalus suckleyi). Humboldt squid, Dosdicus gigas, was opportunistically collected from Southern California. The data resulting from this study will be used to create a food web and has the potential to be extremely useful in developing ecosystem-based management plans.
BIZZARO, JOSEPH J.; EBERT, DAVID A.; YOKLAVICH, MARY K.; KUHNZ, LINDA A.; SUMMERS, ADAM P.. 2013.
(JJB) University of Washington, School of Aquatic and Fishery Sciences, Seattle, WA, USA; (DAE) Moss Landing Marine Laboratories, Moss Landing, CA, USA; (MMY) Southwest Fisheries Science Center, Fisheries Ecology Division, Santa Cruz, CA, USA; (LAK) Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA; (APS) University of Washington, Friday Harbor Laboratories, Friday Harbor, WA, USA
Comparative spatial associations of skates (Rajidae) off central California
Comprehensive knowledge of distribution and abundance patterns is necessary to determine essential fish habitat (EFH) for groundfishes such as skates (Rajidae). Off the US Pacific Coast, where the creation of marine protected areas (MPAs) is a primary regulatory approach of regional fisheries managers, skates are common and abundant components of benthic marine communities. However, reliable information on spatial associations of skates is sparse because of generalized landings data and misidentification. Based on the state of knowledge of skate spatial associations in other regions, the following hypothesis was posited: H1) skates segregate spatially by species and life stage, and exhibit distinct habitat preferences and seasonal shifts in distribution. To test this hypothesis and fill the described knowledge gap, a twenty-year data series (1991-2010) was compiled using a variety of survey techniques and analyzed for the five most abundant skate species (Bathyraja kincaidii, Raja binoculata, R. inornata, R. rhina, R. stellulata) occurring in continental shelf and upper continental slope waters off central California. Multivariate techniques, geostatistics, and regression models were used to: 1) determine EFH for each species/life stage, 2) identify groups of co–occurring species/life stages as habitat guilds, 3) determine species/life stage–specific patterns of distribution and abundance and the processes driving these patterns, and 4) determine areas of high abundance and diversity for the overall skate assemblage. Results will contribute substantially to an improved understanding of the spatial dynamics of skates and skate assemblages, and to the creation of more effective fisheries management strategies off the US Pacific Coast.
BOND, MARK E.; BABCOCK, ELIZABETH A.; CHAPMAN, DEMIAN D.. 2013.
(MEB, DEC) Stony Brook University, Stony Brook, New York, USA; (EAB) University of Miami, Miami, Florida, USA
Southern stingrays concentrate on shallow flats inside marine reserves: response to top-down or bottom-up processes?
Marine reserves release fished species from harvest pressure but their effect on unfished species is unpredictable and may even be negative. Southern stingrays (Dasyatis americana) are not commercially targeted in Belize, but nonetheless are potentially important ecotourism attractions and bioturbators. We used Baited Remote Underwater Video (BRUV©) to survey stingrays in two distinct habitats (flats N=40 and fore-reef N=50) at four sites, two reserves and two otherwise similar fished reefs. A generalized linear model (GLM) is being used to explain the effect of the factors “marine reserve”, “habitat”, “reef type” (atoll or barrier) and a range of environmental variables on the presence of stingrays on BRUVs. Preliminary analysis of BRUV deployments within one reserve and one fished reef found that stingray presence was significantly influenced by “habitat”, but only at the reserve site. Specifically, stingrays were more commonly observed on BRUVs deployed in shallow flats than on the deeper forereef habitats inside the reserve. In contrast, there was no significant effect of habitat on stingray presence at the fished site. We present the full results from all four sites and discuss the potential drivers of this pattern. “Top-down” possibilities include avoidance of deeper habitats due to intimidation by sharks, which we have shown are more common at the reserve sites. “Bottom-up” possibilities include habitat or prey differences between sites. Understanding how marine reserves influence unfished species is intrinsically important given their burgeoning use for marine conservation, and can also provide insights into ecological interactions otherwise difficult to study.
BRAUN, CAMRIN; SKOMAL, GREGORY; THORROLD, SIMON; GERUMEN, MICHAEL.. 2013.
(CB,MB) King Abdullah University of Science and Technology, Thuwal, Saudi Arabia; (ST) Woods Hole Oceanographic Institution, Woods Hole, MA, USA; (GS) Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
Telemetry techniques elucidate Manta alfredii ecology in the eastern Red Sea
Manta spp. are distributed globally in tropical and sub-tropical waters, but local populations appear small and widely dispersed. The reef manta, Manta alfredii, is the smaller, coastal cousin of the two recognized Manta species, and sighting records suggest preferential occupation of nearshore tropical waters with strong site affinity and limited movements. Connectivity among populations is largely unknown, but available evidence suggests regional isolation. While recent efforts have initiated investigation of a few populations worldwide, Red Sea Manta spp. remain completely enigmatic. We use satellite and acoustic telemetry techniques to elucidate short and long-term movements of Manta alfredii in the central Saudi Arabian Red Sea. In addition, we investigate high- resolution dive data of three individuals. These findings enable a better understanding of manta ray ecology in this poorly-studied region. As demand in Asian markets continues to rise, basic information about manta ray behavior and its applicability to regional management efforts become increasingly urgent. Manta spp. harvest and the lucrative ecotourism trade also render this work economically important and could lead to significant local support of conservation efforts.
BROOKS, EDWARD; CONNETT, STEPHEN; LISS, STEPHANIE; KOCH, CHRISTOPHER; STEIN, JEFFREY. 2013.
(EB,CK) Cape Eleuthera Institute, Eleuthera, Bahamas; (SC) University of Florida, Gainesville, Florida, USA; (SL, JS) University of Illinois, Urbana, Illinois, USA
A Fisheries Independent Study Documenting 30-Year Trends in Shark Diversity and Abundance in the Eastern Exuma Sound, The Bahamas
Global declines in elasmobranch populations are well documented; however, the majority of studies rely upon fisheries dependent datasets that are commonly criticized due to the variable nature of fishing techniques over time. Fishery-independent surveys offer a more rigorous approach to detecting long-term changes in abundance and diversity of shark populations. Seasonal surveys were conducted from 1979 through 1981 in an area off the south coast of Eleuthera, The Bahamas. From 2011-2013 these surveys were exactly recreated, with a goal of identifying trends the diversity and abundance of elasmobranchs over the last 34 years. Catches for both historical and modern surveys were dominated by Caribbean reef (Carcharhinus perezi) and tiger (Galerocerdo cuvier) sharks. These two species showed distinct seasonal trends in relative abundance whereby C. perezi were significantly more abundant in the autumn (F=16.64, p=<0.001), in contrast to G. cuvier which were significantly more abundant in the spring (F=8.03, p=0.007). Preliminary analysis indicates a 50.2% reduction in the relative abundance of G. cuvier over the last 34 years (F=4.76, p=0.035), in contrast to a 57.9% increase in the relative abundance of C. perezi in the same period (F=5.73, p=0.021). Changes in catch composition may be the result of differences in the extent of trans- boundary movements between the species, which as a result of the Bahamian longline ban instituted in the 1990s, imposed variable exploitation rates. This study highlights the importance of understanding long-term seasonal movement patterns when designing management and conservation strategies for elasmobranchs.
BROOKS, EDWARDS; SUSKI, CORY; TALWAR, BENDAN; LABELLA, RACHEL; SANFORD, TYLER; COOKE, STEVEN; MANDELMAN, JOHN. 2013.
(EB,BT,RL,TS) Cape Eleuthera Institute, Rock Sound, Eleuthera, Bahamas; (CS) University of Illinois at Urbana-Champaign, Urbana, IL, USA; (SC) Carleton University, Ottawa, ON, Canada; (JM) New England Aquarium, Boston, MA, USA
To chill or not to chill: does on-hook behavior modulate the physiological status of longline-caught sharks
It is clear from past work on elasmobranchs that the magnitude of the acute physiological disturbance and/or subsequent mortality tied to fishing capture varies widely by species. What is not fully resolved, however, is why such differences exist. Recent evidence in one carcharhinid suggests that physiological convalescence is possible while still on a longline hook. Moreover, it is readily apparent that sharks exude differing degrees of vigor while hooked and/or during handling. We therefore hypothesize that the degrees of physiological disturbance and recovery may be intimately linked to behavior while on the longline hook (i.e. the magnitude, duration and cyclicity of escape responses). Through the combined use of video imaging, data logging accelerometers, and blood biochemical profiles, the present study is examining how behavior on a longline relates to physiological status. Preliminary results from Caribbean reef, blacktip, tiger, blacknose and nurse sharks suggest that initial high energy escape responses are terminated 3-5 minutes post hooking and replaced by lower energy circling interspaced with infrequent low energy escape responses. In nurse sharks, heightened activity levels early in the capture event correspond with a maximally disturbed blood biochemical status over short to medium hook durations, and the partial recovery of physiological homeostasis over longer hook durations. This work ultimately hopes to reveal possible strategies (abbreviated soak times, extended gangion lengths, etc.) to enhance survival. Moreover, examining species with divergent phylogenies, life histories and respiratory strategies can help signify those taxa more susceptible to capture-stress, and inform specific broader-scale fishery management strategies.
BUCKHORN, MICHELLE; KETCHUM, JAMES; SLAGER, CHRISTINA; LKIMELY, PETER. 2013.
(PK_ University of California, Davis, Davis, California, USA; (CS) Aquarium of the Bay, San Francisco, California, USA; (MB) Prince William Sound Science Center, Cordova, Alaska, USA; (JK) Pelagios Kakunjá, A.C., La Paz, Mexico
Movements and residency of sevengill sharks (Notorhynchus cepedianus) in San Francisco Bay
The diel movements and seasonal residence of adult cow sharks are described in San Francisco Bay. Four adult sevengill sharks were tracked continuously for periods as long as five days. The sharks displayed rheotaxis in response to the tidal cycle. For example, a male cow shark exhibited the same pattern during successive days: 1) swimming non- directionally in the center of the bay during daytime in slow flows, 2) swimming out of the bay in a highly directional manner up in the water column during the evening in strong outward flows, 3) descending to the bottom and moving non-directionally in the mouth of the bay during slow flows, and 4) rising in the water column and returning to the bay in a direct path traveling in strong inward flows. Coded ultrasonic beacons were placed on 21 sharks. Their seasonal tenure in the bay was determined over a period of three years by multiple cross-bay arrays of tag-detecting monitors. The adult males and females resided just inside the bay, being detected frequently at the paired Golden Gate array. The subadult males and females occupied the interior of the bay. The adults sharks were absent in the winter but were present from early spring to late fall. Sevengills tagged in the bay were detected during the winter months in the coastal waters off San Diego, over six hundred kilometers away, indicating that they make extensive annual migrations between the temperate latitudes.
CARLISLE, AARON; LITVIN, STEVEN; MADIGAN, DANIEL; GOLDMAN, KENNETH; KIM, SORA; BLOCK, BARBARA. 2013.
(AC,SL,DM,BB) Hopkins Marine Station of Stanford University, Pacific Grove, CA, USA; (KG) Alaska Department of Fish and Game, Homer, AK, USA; (SK) University of Wyoming, Laramie, WY, USA
Use of the California Current as a nursery area by juvenile salmon sharks
The use of nursery areas by elasmobranchs is an important life history strategy that is believed to reduce mortality and/or increase growth rates. The endothermic salmon shark (Lamna ditropis) is believed to use the California Current System (CCS) as a nursery area, though outside of their occurrence in the CCS, nothing is known about habitat use or trophic ecology of juveniles. Studying how juvenile salmon sharks use the CCS has been limited by access to small sharks; however, young sharks consistently strand along the west coast of North America, providing an opportunity to study these animals using methodologies that do not require live specimens. We used records of stranding events to describe the spatial and temporal pattern of strandings and inform our understanding of distribution patterns. We also collected tissues for stable isotope analysis (SIA) from stranded sharks to examine trophic ecology and habitat use of juvenile sharks in the CCS, in particular to identify likely prey and habitats used by juvenile sharks. By integrating these two data sources, we are able to describe general patterns of distribution, habitat use, and diet of juvenile sharks in the CCS, and offer some theories about why strandings may occur.
CARLSON, AMY; SULIKOWSKI, JAMES. 2013.
University of New England, Biddeford, Maine, USA
Horizontal and Vertical Movement Patterns of Northwestern Atlantic Spiny Dogfish (Squalus acanthias)
Spiny dogfish (Squalus acanthias) are assumed to be a highly migratory species, making habitual north-south migrations throughout their Northwestern Atlantic U.S range.
Also assumed to be a benthic species, spiny dogfish stock structure is estimated through NEFSC bottom trawl surveys. Recent anomalies in population trends, including a recent four-fold increase in spawning stock biomass, suggest alternative movement behaviors may exist for this species. To obtain a better understanding of the horizontal and vertical movement dynamics of this species, Microwave Telemetry Pop-off Satellite Archival X-Tags have been attached to forty adult spiny dogfish at the northern (Gulf of Maine) and southern (North Carolina) extents of their central U.S. geographic range.
Reconstructed geolocation tracks, ranging in lengths from 2 to 12 months, suggest that the seasonal migration patterns may be local in nature to the respective deployment sites which differs from the previously published paradigms. Significant differences in distance between deployment origin and geolocations indicate two unique migration patterns, further supported by kernel utilization distribution models suggesting strong separate core home ranges between the tagging locations. Between the two regions, significant differences were also noted in abiotic preferences, such as temperature, depth, and distinct diel movements. In addition, vertical preferences indicate this species may not utilize the benthos as previously thought. The results of the current study suggest regional management of the species may be more appropriate, and coastwide NEFSC bottom trawl surveys may not be as accurate at estimating spiny dogfish populations as once perceived.
CARTER, LACIE; KERSTETTER, DAVID. 2013.
Nova Southeastern University, Dania Beach, Florida, USA
Elasmobranch Sensory Stimulation as a Bycatch Reduction Technique in Commercial Fisheries
Incidental catch of elasmobranchs on hooks intended for target species in commercial fisheries may have negative impacts on commercial fisheries, ecosystem dynamics, and conservation efforts. Recent studies have sought to repel sharks from baited hooks by stimulating the elasmobranch sensory system. This study follows this idea: a small epoxy-based capsule has been designed that, when immersed in water, emits a small electrical signal. These capsules, placed slightly above baited hooks, will be field tested in commercial longline fisheries with the intention is that sharks will be attracted to the bait, but then get distracted by the capsule before ingesting the bait and being caught. At the time of this writing, field tests are in process, and results will be presented at the Joint Meeting of Ichthyologists & Herpetologists in July 2013.
CHABOT, CHRIS L.. 2013.
UCLA, Los Angeles, CA, USA
A comparison of the frequency of multiple paternity between two populations of the brown smoothhound shark, Mustelus henlei
Multiple paternity was recently observed in a population of the brown smoothhound shark, Mustelus henlei, from Las Barrancas, Baja California Sur, Mexico with litters demonstrating the greatest percentage of multiple paternity for any shark species (0.93 of litters and an average number of sires = 2.3). To determine if this frequency is consistent elsewhere in the species’ range, 4 polymorphic microsatellite loci were used to determine the frequency of multiple paternity in 18 litters of M. henlei from Santa Catalina Island, CA sampled in 2004, 2008, and 2012. Overall, multiple paternity was detected in 0.22 of litters with an average of 1.3 sires per litter. Multiple paternity varied among sampling periods with 2004 demonstrating multiple sires for 0.4 of sampled litters (n = 10) and 2008/2012 demonstrating a total lack of multiply sired litters (n = 8). Although multiple paternity was detected in this study, the frequency of occurrence is lower than that observed in the Mexican population. Based on these findings, investigators should take location into consideration when assessing the existence of multiple paternity in future studies of elasmobranch species.
CHABOT, CHRIS L.. 2013.
UCLA, Los Angeles, CA, USA
Population connectivity of the brown smoothhound shark, Mustelus henlei, in the northeastern Pacific and the Gulf of California
To determine the effects of the prominent biogeographic and phylogeographic barriers of the northeastern Pacific (Point Conception, the Los Angeles Region, and the Peninsula of Baja California) on the population connectivity of the temperate brown smoothhound shark, Mustelus henlei (Triakidae), data from the mitochondrial control region (mtCR) and six nuclear microsatellite markers were used 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, Mexico, and the northern Gulf of California). Microsatellite data demonstrated significant contemporary gene flow among all localities with mtCR sequence data detecting significant structure between both San Francisco Bay and Santa Catalina Island and all other localities. Based on these results, female philopatry to the known nursery of San Francisco Bay may have been detected as well as the identification of a putative nursery at Santa Catalina Island. Furthermore, the barriers of the northeastern Pacific seem to have little effect on the contemporary population connectivity of M. henlei.
CHRISTIANSEN, HEATHER; HUSSEY, NIGEL; WINTNER, SABINE; CLIFF, GEREMY; DUDLEY, SHELDON; FISK, AARON. 2013.
(HC,NH,AF) Great Lakes Institute for Environmental Research, University of Windsor, Windsor, On, Canada; (SW,GC,SD) KwaZulu-Natal Sharks Board, Umhlanga Rocks, South Africa
Sample preparation techniques for stable isotope analysis of elasmobranch vertebrae
Stable isotope analysis (SIA) provides an important ecological tool to study the feeding and movement dynamics of animals. Elasmobranch vertebrae can be serially sampled to obtain an isotopic history of an individual from birth to death. It has been suggested that elasmobranch vertebrae must be decalcified before undertaking SIA because the inorganic portion of the vertebrae may affect isotopic values. In this study, we used three species of shark (white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and sand tiger (Carcharias taurus)) to study the effects of sample preparation techniques on shark vertebral isotopic compositions. First, we determined the minimum sample weight required to obtain an accurate and consistent isotopic value on our IRMS (Isomass Delta V) using a non-dilution program. We then compared the isotopic values of untreated vertebrae vs. vertebrae treated with ethylenediaminetetraacetic acid (EDTA). We found no significant difference in δ13C values for white and tiger sharks between treatments, but for sand tigers differences were observed. There was no significant difference between δ15N values of treated and untreated samples for any species. Lastly, the percent yield of material for SIA following standardized EDTA treatment also varied among species. Given these results it is recommended that EDTA treatment is unnecessary for SIA of white and tiger shark vertebrae, however it may be necessary for sand tiger sharks. We recommend conducting a preliminary study investigating the weight of vertebral material required to obtain a reliable isotopic value and to determine if EDTA treatment is needed specific to your species and instrument.
CHIRSTIANSEN, HEATHER; LIN, VICTOR; TANAKA, SHO; VELIKANOV, ANATOLY; MOLLET, HENRY; FISK, AARON; HUSSEY, NIGEL. 2013.
(HC,AF,NH) Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada; (VL) Taipei, Taipei, Taiwan; (ST) School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka, Japan; (AV) Sakhalin Research Institute of Fisheries & Oceanography, Yuzhno-Sakhalinsk, Russia; (HM) Moss Landing Marine Laboratories, Moss Landing, CA, USA
The last frontier: catch records of white sharks (Carcharodon carcharias) in the Northwest Pacific Ocean
White sharks are globally distributed apex predators in temperate, sub-tropical and tropical waters. Our knowledge of their biology and ecology has increased recently based on dedicated research at aggregation sites. For the Northwest Pacific Ocean, little is known regarding white sharks aside from short notes documenting occurrence. This study provides a comprehensive meta-analysis of 240 observations of white sharks from the Northwest Pacific Ocean between 1951 and 2013. Records include by-catch in commercial fisheries, from shark attacks and personal observations and were documented from China (32), Japan (129), the Philippines (1), Russia (8), South Korea (22), Taiwan (45) and Vietnam (3). The highest percentage of observations (42%) occurred April-June (spring). Sex was recorded for 113 observations (53 male and 60 female), with no significant difference of sex by country. Of the 60 females recorded 11 were pregnant with individuals ranging from the beginning stages of pregnancy (egg cases present) to near term (1.4 m embryos); on average five embryos were found per litter with a maximum of 10. The smallest shark was 1.3 m total length and weighed 16 kg captured near Popov Island, Russia. The largest shark was 6.02 m total length captured in the East China Sea, while the heaviest shark weighed 2530 kg (Guang Zhou, China). These observations indicate there is a resident population of white sharks in the Northwest Pacific Ocean and given limited data available on this CITES and IUCN Red Listed species, there is a need for dedicated research to assist regional management planning.
CHURCHILL, DIANA; HEITHAUS, MICHAEL; GRUBBS, R. DEAN. 2013.
(DC, MRH) Florida International University, Miami, FL, USA; (RDG) Florida State University, Tallahassee, FL, USA
Trophic variation within and among hagfish species, a numerically dominant scavenger in the Gulf of Mexico
Hagfish are a numerically dominant benthic scavenger and predator present in the deep-sea communities of the Gulf of Mexico (GoM). Very little attention, however, has focused on the trophic interactions of jawless fish in these communities. We used stable isotope analysis (δ13C and δ15N) to describe the trophic interactions of three species of hagfish (Eptatretus minor, Paramyxine springeri and Myxine mcmillanae) relative to the rest of the deep-sea fish and scavenger community in GoM. Hagfish (n=217) were collected along the northern slope of the eastern GoM using benthic traps. Because of the highly variable lipid content found in hagfish muscle tissue, we lipid-extracted samples. Lipid extraction resulted in considerable shifts in δ13C and δ15N, which both correlated to bulk muscle C:N ratios. After lipid extraction, hagfish isotope values covered a considerable range for both δ13C (-19.70 to -14.15) and δ15N (6.05 to 15.05) relative to overall variation in the deep-sea community. Neither δ13C nor δ15N varied with total length for any species. Also, δ13C or δ15N values did not differ between E. minor and P. springeri, but both species showed lower values of δ13C and δ15N than M. mcmillanae. Interestingly, δ15N values of E. minor and M. mcmillanae were similar to larger deep-sea predators (sharks and teleosts) but P. springeri had the lowest mean δ15N value of all species (n = 13) sampled. This study represents important baseline information regarding the trophic interactions and variation in stable isotope values within hagfish in the GoM.
CLERKIN, PAUL; EBERT, DAVID; NAYLOR, GAVIN. 2013.
(PC,DE) Moss Landing Marine Laboratories, Moss Landing, California, USA; (GN) Hollings Marine Laboratory, Charleston, West Virginia, USA
Reproductive biology and maturity of deep-sea sharks in the Southern Indian Ocean
Examination of chondrichthyans from a survey of Southern Indian Ocean seamounts aimed to: 1) survey species in this region, 2) construct a phylogenetic framework of chondrichthyans based on DNA samples as part of the Assembling the Tree of Life project, and 3) assess life history characteristics of elasmobranch bycatch. The trawler operated southeast of Madagascar within an area bounded by 29o — 40o S and 43o — 54o E where seamounts appear to be hotspots of biodiversity. Reproductive and maturity data including sex, length, maturity stage, oviducal gland development, egg width, and number of eggs were recorded from 2,400 chondrichthyans and analyzed. Approximately 400 specimens of the genera Centrophorus, Deania, Centroscymnus, Centroselachus, Proscymnodon, Zameus, Etmopterus, Dalatias, Apristurus, Parmaturus, Pseudotriakis, Hydrolagus, and Chimaera were collected between depths of 500m – 1,500m. Additional data includes: 710 tissue samples for DNA studies, 225 vertebrae and spines for age/growth studies, and diet data recorded qualitatively from sharks including poorly known species, e.g., Proscymnodon plunketi and Pseudotriakis microdon, as well as several undescribed species of Etmopterus, Apristurus, Parmaturus, Hydrolagus, and Chimaera. Project specimens have been deposited the American Museum of Natural History, California Academy of Sciences, and the Smithsonian Natural History Museum. The expedition was an international collaboration between the Pacific Shark Research Center, Moss Landing Marine Laboratories, Hollings Marine Laboratory, College of Charleston, Southern Indian Ocean Deepsea Fishers Association, Sealord Corporation, New Zealand, and the Mauritius Ministry of Fisheries. This project was funded, in part, by NSF grant: DEB 1132229.
COCHRAN, JESSE; BRAUN, CAMRIN; THORROLD, SIMON; SKOMAL, GREG; BERUMEN, MICHAEL. 2013.
(JC,CB,MB) The King Abdullah University of Science and Technology, Thuwal, Makkah, Saudi Arabia; (ST) Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA; (GS) Massachusetts Division of Marine Fisheries, Massachusetts, USA
Habitat Use in Aggregating Red Sea Whale Sharks
The whale shark (Rhincodon typus) is known to aggregate seasonally in specific sites within its circumglobal range. The recent discovery of an aggregation site on Rope Reef (an inshore reef off the coast of the Saudi Arabia) has provided a starting point for whale shark research in the Red Sea. In March-May of 2010 an array of 32 acoustic receivers was installed on and around Rope Reef. Seventy-five whale sharks (28 male, 30 female, 17 undetermined) were fitted with acoustic tags in 2010, 2011, and 2012. Thirty-three of these sharks were also fitted with satellite tags during the 2010 and 2011 seasons. The acoustic data shows 85% of all detections have occurred in April or May. Over 90% of detections were made by receivers installed on Rope Reef. More than half of Rope Reef detections occurred at its northwest corner (25% of total effort). Both the acoustic and sighting data suggest parity and integration of the sexes within this population. Finally, approximately 40% of tagged sharks are detected again the following year. Satellite data shows that 15 of these phylopatric sharks migrated hundreds of kilometers from the Rope Reef in between aggregation seasons. Describing the characteristics of this aggregation provides a baseline by which to guide the efforts of future whale shark studies in the area and in the greater Red Sea.
DALY-ENGEL, TOBY; GRUBBS, R. DEAN. 2013.
(TDS) University of West Florida, Pensacola, Florida, USA; (RDG) Florida State University Coastal and Marine Laboratory, St. Teresa, Florida, USA
Aloha Dogfish: Description of a New Shark Species from Hawaii
Dogfish of the genus Squalus are small, deeper-water sharks with a slow rate of molecular evolution that has led to their designation as a series of species complexes, with low between-species diversity relative to other taxa. The shortspine spurdog, Squalus mitsukurii, is a medium-sized dogfish common to warm shelf and seamount habitat, with a putative circumglobal distribution that has come under investigation recently due to geographic variation in meristics, morphometrics, and genetic diversity. We examined the Hawaiian population of S. cf mitsukurii using both morphometrics and genetic techniques and compared it to the type population in the West Pacific (Japan). External morphology differs with respect to head and interdorsal length, and molecular analysis of both the mitochondrial NADH2 gene and CO1 (barcoding region) show divergence with significant bootstrap support. Between-species diversity was low, but at least five-fold greater than within-species diversity and consistent with others in the S. mitsukurii complex. We suggest that Squalus cf mitsukurii from Hawaii be designated as a distinct species, and both a new name and a holotype assigned.
DAVIS, JOHNATHAN. 2013.
(JD) University of New Orleans, New Orleans, LA, USA; (JD) University of Auckland, Auckland, New Zealand
The Bull Sharks of Lake Pontchartrain
Lake Pontchartrain is a productive estuarine ecosystem in Louisiana which provides food and protective habitat for coastal marine species including bull sharks (Carcharhinus leucas). I assessed fish assemblage data collected using multiple gear types (trawl, beach seines, and gillnets) from July 2000 to June 2011. Gillnet data collected during warmer months (May-September) from known bull sharks areas revealed that C. leucas were caught ~20% of the time. My analyses revealed trends in the occurrence and distribution of C. leucas. With this information, I will attempt to further understand C. leucas ecology in Lake Pontchartrain. Movement and distribution of C. leucas will be assessed using an acoustic receiver monitoring array. Acoustic transmitters will be surgically implanted in individual C. leucas and sharks will be tracked with an array that has been deployed in Lake Pontchartrain and surrounding habitats. These data will provide information about habitat preferences, water quality preferences, and seasonal distributions. These data will also provide insight into where juvenile C. leucas are distributed during the cooler winter months as well as the size and age at which they leave the estuary. Little is known about the distribution of C. leucas in these oligohaline habitats so this will be the first study of its kind for this species in Lake Pontchartrain.
DAIVS, JOHNATHAN. 2013.
(JD) University of Auckland, Auckland, New Zealand; (JD) University of New Orleans, New Orleans, LA, USA
Movement and Behavior of the New Zealand Eagle Ray, Myliobatis tenuicaudatus
The New Zealand eagle ray (Myliobatis tenuicaudatus) is an intertidal species that has developed the ability to utilize highly productive intertidal habitats and avoid stranding. It has been suggested that the use of tidal information, particularly orientation to water current, may be used to avoid stranding on an outgoing tide. The movements of M. tenuicaudatus in relation to the tidal change were assessed by tracking individuals in an estuary. Data were analyzed using GPS data-loggers, telemetry transmitter and receivers, and behavioral modeling software. The models show use of the tides for transiting movement in and out of the estuary during rising and falling tides. The movement data also show that M. tenuicaudatus rests and feeds in channels of the lower part of the estuary at low tide while occurring over the mudflats during high tide. In addition to the fieldwork, two tanks were fitted to simulate the tidal cycle by changing water flow direction every six hours and ~12-15 minutes with 15 minutes of slack tide in between. Two juvenile eagle rays were placed in these tanks and behavior was recorded for 13 days. Both animals exhibited positive rheotaxis approximately 100% of the time during rest. When flow changed, both animals reacted within 90 seconds by turning and facing the new current direction. When food was present both animals exhibited negative rheotaxis approximately 100% of the time which suggests the utilization of tidal flow to search for food. This is consistent with orientation behavior and movements observed in the field.
DRYMON, MARCUS; CARASSOU, LAURE; POWERS, SEAN. 2013.
University of South Alabama, Mobile, Alabama, USA
Multi-scale Investigation of the Factors Affecting the Distribution of Sharks in the Gulf of Mexico
Successful management of marine populations requires a spatial alignment between ecological and managerial scales. This is particularly true, yet difficult, for large, highly migratory fish such as sharks. Catch data from two fishery-independent bottom longline surveys, as well as multiple ancillary datasets representing primary and secondary productivity, physiochemical parameters and forage fish abundance were examined to better understand the mechanisms driving the distribution of sharks in the Gulf of Mexico (GOM). For this analysis, we considered basin-wide (hundreds of kilometers) as well as regional (tens of kilometers) scales, centered on the 88th W parallel of the Gulf of Mexico. Multivariate statistical tools were used to examine the relationship between shark community structure and location across the GOM (using centered PCA), and primary/secondary productivity and location (using normed PCA). These matrices were then related using a co-inertia analysis. Results from our basin-scale analysis indicated that Atlantic sharpnose sharks (Rhizoprionodon terraenovae) were associated with high crustacean biomass, while species such as spinner (Carcharhinus brevipinna) and blacktip (C. limbatus) sharks were correlated to fish biomass and ChlA concentrations. The same series of analyses were then repeated on a regional scale to examine how spatial scale affects the factors influencing the distribution of these predators in the GOM. Our data suggest the importance of combining and analyzing data spanning multiple trophic levels, and have implications for the spatial scales upon which future elasmobranch management plans should be constructed.
FELDHEIM, KEVIN; GRUBER, SAMUEL; DIBATTISTA, JOSEPH; BABCOCK, ELIZABETH; KESSEL, STEVEN; HENDRY, ANDREW; PIKITCH, ELLEN; ASHLEY, MARY; CHAPMAN, DEMIAN. 2013.
(KF) Field Museum of Chicago, Chicago, IL, USA; (SG,EB) University of Miami, Miami, FL, USA; (JB) King Abdullah University, Thuwal, Saudi Arabia; (SK) Great Lakes Institute for Environmental Research, Windsor, Ontario, Canada; (AH) McGill University, Montréal, Québec, Canada; (EP,DC) Stony Brook University, Stony Brook, NY, USA; (MA) University of Illinois at Chicago, Chicago, IL, USA
Twenty-year pedigree yields first evidence of geographically precise natal philopatry in sharks.
Geographically precise natal philopatry is not well known in late-maturing marine species, including sharks and their relatives (Class Chondrichthyes). A genetic-based pedigree of lemon sharks (Negaprion brevirostris) sampled from 20 consecutive cohorts (1993-2012) at Bimini, Bahamas showed that certain females faithfully gave birth at this site for nearly the entire period. Six females born from 1993-1997 returned to give birth 14-17 years later. This is remarkable considering that only 15 females (95% C.I. 8-25) from these cohorts are likely to have survived to maturity and Bimini represents < 2.5% of available nursery habitat within a conservative estimate of their dispersal range. Long-term fidelity to nursery sites and geographically precise natal philopatry highlights the merits of emerging spatial and domestic conservation efforts for these threatened predators.
FINGER, JEAN SEBASTIENL GUTTRIDGE, TRISTAN; WILSON, ALEXANDER; DOCHTERMANN, NED; GRUBER, SAMUEL; KRAUSE, JENS. 2013.
(SG) Bimini Biological Field Station, Bimini, Bahamas; (JSF,JK) Humboldt University, Berlin, Germany; (TG) School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK; (AW) Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department of Biology and Ecology of Fishes, Berlin, Germany; (ND) Department of Biological Sciences, North Dakota State University, Fargo, ND, USA
Investigating personality in juvenile lemon sharks (Negaprion brevirostris)
Animal personality has gained a lot of interest in the last decade and it is now clear that most animals (from vertebrates to invertebrates) have personality. Personality in animals represents behavioral consistency, meaning for instance that a bold individual will stay bold in every situation relative to a shy individual. The recent boom in personality studies comes from the far reaching implications from both an evolutionary as well as an ecological point of view. It is therefore important to investigate the presence of personality in elasmobranch fishes. This project is based on behavioral observations in different contexts such as sociability and novel environments in the juvenile lemon shark (Negaprion brevirostris). An experimental pen was designed to assess six sharks for these latter tests per day in two nurseries. During the year 2012, lemon sharks (n=121) were tested and among these sharks 80 were retested. Results revealed that juvenile lemon sharks posses a social and explorative personality that stayed consistent over a 6 month period. Furthermore, in one of the nurseries a strong correlation between exploration and sociability was found being the first demonstration of behavioral syndromes in elasmobranches and illuminating an interesting difference between the two tested populations. In the following year, the large sample size that will be accumulated by this method will allow us to investigate the genetic component of personality and the relationship between personality type, growth rate and survival along with testing personality in their natural environment.
FISHER, ROBERT; CALL, GARRETT; MCDOWELL, JAN. 2013.
(RF, JM) Virginia Institute of Marine Science, Gloucester Point, VA, USA; (GC) Tufts University, Cummings School of Veterinary Medicine, North Grafton, MA, USA
Reproductive Anomalies in Cownose Rays (Rhinoptera bonasus) from Chesapeake Bay
This study marks the first observation of multiple embryos and right uterus functionality in cownose ray, Rhinoptera bonasus. The recovery of a three-quarter term albinistic cownose ray embryo through necropsy is also reported. A total of eight episodes of multiple embryos in cownose rays are reported herein. Two sets of twin live births from captive rays and six separate in utero multiple embryos discovered during necropsy of fishery dependent and independent acquired samples were observed. All multiple embryos were developing in the left uterus. Live births occurring in captivity were confirmed to be two sets of twins through direct sequencing a portion of the mitochondrial DNA from the newborn pups and putative mothers. Cownose ray have paired reproductive tracts, and previously functionality was reported only in the left oviduct. This is the first reporting of gestation in the right oviduct in cownose ray, with first quarter and third quarter embryos removed from the right uterus of two female rays.
FORDHAM, SONJA. 2013.
Shark Advocates International, Washington, DC, USA
Preventing the Predictable Depletion of U.S. Atlantic Cownose Rays
(Rhinoptera bonasus)
U.S. east coast fishing representatives have devised campaigns to promote local and international consumption of cownose rays (Rhinoptera bonasus) taken primarily as bycatch in Mid-Atlantic fisheries. Industry interest in developing new markets for commonly caught species is bolstered by widespread belief that cownose rays are preying dangerously on commercially valuable bivalves, such as oysters, scallops, and clams. Promoters of cownose ray consumption have used scientific findings on the role of R. bonasus in bivalve depletion (which are disputed) to mischaracterize these rays as overly abundant, invasive, nuisance species. Given the extremely low fecundity of cownose rays, fishing mortality must be tightly controlled to avoid overexploitation and population collapse. Yet, years after commercial interest in cownose rays was sparked, there are no U.S. Atlantic cownose ray population assessments or fishing limits. State managers are open to taking conservation action, despite relatively low public pressure to do so, but lack technical advice for basing measures. There is interest in creating incentives for fishery improvement though sustainable seafood initiatives, but specific projects are not progressing as swiftly as planned. The main cownose ray retailer does not sell shark due to sustainability concerns, reflecting significant inconsistencies in public awareness and concern with respect to elasmobranchs. Increased engagement by scientists, conservationists, consumers, and managers is needed to ensure cownose ray fishing is kept to sustainable levels. This presentation will review the recent history of cownose ray characterization and commercialization in the Mid-Atlantic region, and include recommendations for action aimed at a range of interested parties.
FRAZER, BRYAN; DRIGGERS, WILLIAM; LOEFER, JOSH; ADAMS, DOUGLAS; JONES, CHRISTIAN. 2013.
(BF) College of Charleston, Charleston, SC, USA; (BF) South Carolina Dept of Natural Resources, Charleston, SC, USA; (WD, CJ) National Marine Fisheries Service, Southeast Fisheries Science Center, Pascagoula, MS, USA; (DA) Florida Fish and Wildlife Conservation Commission, Melbourne, FL, USA; (JL) University of South Carolina, Columbia, SC, USA
Validated Age and Growth of the Bonnethead, Sphyrna tiburo, in the western North Atlantic Ocean
Age and growth of the bonnethead Sphyrna tiburo, was examined in coastal waters off the east coast of the US. Vertebrae were collected and aged from 329 females and 216 males. Sex specific von Bertalanffy growth curves were fitted to length at age data. Female von Bertalanffy parameters were L¥= 1032 mm FL, k= 0.18, to = -1.75, and Lo=291mm FL. Males reached smaller theoretical asymptotic length, and had a slower growth coefficient, with von Bertalanffy parameters being L¥= 778 mm FL, k= 0.30, to = – 1.50, and Lo= 281 mm FL. Maximum observed age was 17.9 and 12.0 years for females for males. Annual deposition of growth increments was verified by marginal increment analysis and validated through recapture of 13 OTC injected specimens. Annual band deposition was validated for age classes 2.5+ to 10.5+ with times at liberty ranging from 1 to 4 years. Age at 50% maturity was 6.6 years and 3.9 years for females and males. von Bertalanffy growth parameters were compared to growth parameters from bonnethead in the eastern Gulf of Mexico (GOM) to test for differences. Female and male bonnetheads in the SAB had a significantly higher theoretical asymptotic length, lower coefficient of growth, and lower estimated mean size at birth. Maximum observed age and age at 50% maturity were higher for both sexes in the SAB. Significant differences in age and growth parameters and evidence from tagging studies suggest that for management, bonnethead sharks in the SAB and GOM should be considered separate stocks.
GALLAGHER, AUSTIN; ORBSEN, ERIC; HAMMERSCHLAG, NEIL; SERAFY, JOSEPH. 2013.
(AG,JS) Leonard and Jayne Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA; (EO) National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, FL, USA; (NH) Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
Relative Vulnerability of Sharks to the US Atlantic Pelagic Longline Fishery
Bycatch occurs in virtually all fisheries worldwide, and has been implicated as a major driver of the declines for numerous marine fish stocks, including species of shark that are now classified as threatened. The present study examines the hooking survival (i.e., proportion of live fish upon gear retrieval) of 12 shark species that are routinely caught in the US Atlantic pelagic longline fishery. The data examined were collected by the US NMFS Pelagic Observer program from 2005 to 2012. Logistic regression was used to test the hypothesis that fishery target has no impact on shark hooking survival. Soak time, temperature, hook depth and shark size were included as factors in the regression models. Results suggested significant survival differences according to fishery target for one-third of species with a pattern of greater survival during tuna versus swordfish fishing. Overall, rankings of shark species vulnerability were similar with night shark and scalloped hammerhead being the most and tiger shark being the least susceptible to the longline gear interaction. Results are discussed within an ecological risk assessment framework that considers how species-specific differences in phylogeny, physiology, and ecological and functional specialization may affect survival.
GELSLEICHTER, JIM. 2013.
University of North Florida, Jacksonville, FL, USA
Androgen production and function in male elasmobranch reproduction
Because of their phylogenetic position and diverse array of breeding strategies, sharks and their relatives are an interesting taxon for investigating the evolution and function of hormones involved in reproduction. Despite this, however, the reproductive endocrinology of cartilaginous fishes has been poorly studied in comparison with that in other major vertebrate groups, and many of the endocrine pathways typically involved in vertebrate reproduction remain largely uncharacterized in these fishes. In this review, I will discuss the results of our laboratory’s efforts to better understand the reproductive endocrinology of male sharks and rays, highlighting research on the role of androgens in reproductive tract function. Topics such as sites of androgen production, circulating androgen concentrations, and androgen receptor distribution in reproductive organs of male sharks and rays will be discussed.
GIRESI, MELISSA; GRUBBS, R. DEAN; PORTNOY, DAVID; GOLD, JOHN. 2013.
(MG,DP,JG) Texas A&M University, College Station, TX, USA; (RDG) Florida State University, St. Teresa, FL, USA
Morphologically conserved, genetically diverged; A key to distinguish among smoothhound sharks in the U.S. Atlantic
Smoothhound sharks (Family Triakidae, Genus Mustelus) are found circum-globally and represent one of the most speciose genera among extant sharks. Although many of these species are morphologically conserved, advances in molecular methods and increased interest in biodiversity over the last decade, have led to the description of twelve new smoothhound species since 2005. Consequently, verifying the distribution of individual species, as well as articulating strategies for their management and conservation, remains problematic. Here, we discuss the use of both molecular and morphological markers to assess differences among smoothhound species in the U.S. Atlantic and present a reliable morphological key to distinguish among the smoothhound species (Mustelus canis, Mustelus norrisi, and Mustelus sinusmexicanus) in the Gulf of Mexico.
GOLDMAN, KENNETH. 2013.
Alaska Department of Fish and Game, Homer, AK, USA
An update on the thermal physiology and reproductive biology of salmon sharks, Lamna ditropis
Salmon sharks, Lamna ditropis, belong to the Family Lamnidae; a small group of sharks that possess vascular counter-current heat exchangers (retia mirabilia) allowing retention of metabolically generated heat, resulting in elevated body temperatures. Recently, deep red muscle temperature data have been obtained to enhance our understanding of the thermal capacity of this species. Data show that free-swimming adult salmon sharks maintain a specific body core temperature independent of changes in ambient temperature through a combination of physical and physiological means, and essentially function as homeotherms. Current work on their reproductive biology provides further evidence of a two year reproductive cycle with an approximately nine month gestation period in the reproductive year.
DE ACEVEDO, MELISSA GONZALES; GELSLEICHTER, JIM; FRAZER, BRYAN; BELCHER, CAROLYN. 2013.
(MGA,JG) University of North Florida, Jacksonville, Florida, USA; (BF) Department of Natural Resources, Charleston, South Carolina, USA; (CB) Department of Natural Resources, Brunswick, Georgia, USA
Preliminary 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. Preliminary 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 will 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.
MORALES, MILLKE JASMINE ARMININI; OLIVIERA, CLAUDIO; MENDONÇA, FERNANDES; COELHO, RUI; SANTOS, MIGUEL NEVES; FAUSTO FORESTI. 2013.
(MJAM,CO,FFM,FF) Instituto de Biociências, UNESP, Botucatu, São Paulo, Brazil; (RC) Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Faro, Algarve, Portugal; (MNS) Instituto Português do Mar e da Atmosfera (IPMA, I.P.), Olhão, Algarve, Portugal
Population genetic structure of the bigeye thresher shark, Alopias superciliosus, using mitochondrial DNA control region, in a comparison between the Atlantic and Indian Oceans
The bigeye thresher shark, Alopias superciliosus, is a highly migratory species that occurs in oceanic and coastal areas of all Oceans, particularly in tropical regions. It is currently assessed as globally “Vulnerable” by the IUCN (International Union for the Conservation of Nature) because of its population declines in the past years. Considering the scarcity of information regarding the biology and population genetics of this species, the current study sought to characterize the genetic population structure of A. superciliosus, comparing samples from the Atlantic and Indian Oceans. Sequences of mitochondrial DNA from the control region (D-loop) were used, with 913 bp (base pairs) analyzed from 122 specimens from the Atlantic and 11 specimens from the Indian Ocean. Considering all the samples, both from the Atlantic and Indian Oceans, only eight haplotypes were found, with one of the haplotypes shared by 93.2% of the analyzed sharks. These results suggest a very low genetic variability (π = 0.00121 ± 0.00042 and h=0.131 ± 0.040), no population structure (no significant ΦST value), and an intense gene flow across the studied areas, even between the two Oceans. Therefore, for fisheries management and species conservation purposes, a single A. superciliosus stock should be considered in the entire sampled area, with this low genetic variability suggesting a natural fragility of the species. Furthermore, it seems the bigeye thresher sharks have the ability of migrating between those two regions of the Atlantic and the Indian Oceans.
GONZALES-JURADO, DOM. 2013.
UCLA, Los Angeles, CA, USA
Seasonal, Geographic, and Ontogenetic Feeding Ecology of Eastern Pacific Angel Sharks
Angel sharks are primarily benthic dwelling sharks found mainly in temperate and sub- tropical parts of the Atlantic and Pacific Oceans. Their primary method of capturing prey is by ambushing anything small enough to be swallowed by rapidly lunging from a sedentary position on the sea floor. In the eastern North Pacific angel sharks are thought to be generalist predators that exhibit geographic variation in their diet compositions in different environments across their range. In the Southern California Bight blacksmith (Chromis punctipinnis) are the most prevalent prey and in the Southern Gulf of California jack mackeral (Decapterus macrosoma) are the most prevalent prey item. Curiously, no significant ontogenetic shifts in diet have been previously documented, which would suggest that the sharks might exhibit a local preference for a particular species. In this study the stomach contents of 71 angel sharks from across the Pacific Ocean and the Gulf of California surrounding the Baja California peninsula were examined and used to describe patterns of seasonal, geographic, and ontogenetic feeding habits of these sharks across their range.
GRAY, TEAGEN; BERNARD, ANDREA; CLAKE, SHELLEY; CHAPMAN, DEMIAN; MCAULEY, RORY; GERAGHTY, PASCAL; SHIVJI, MAHMOOD. 2013.
(TG,AB,MS) Save Our Seas Shark Center, Dania, FL, USA; (SC) Oceanic Fisheries Programme, Secretariat of the Pacific Community, BPD5 CEDEX, Noumea, New Caledonia; (DC) School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, USA; (RA) Department of Fisheries, Government of Western Australia, Hillarys, WA, Australia; (PG) Department of Primary Industries, Cronulla Fisheries Research Center of Excellence, New South Wales, Australia
Global population structure of the dusky shark and geographic sourcing of shark fins from commercial markets – Updated results
The dusky shark, Carcharinus obscurus, is a globally distributed, coastal- pelagic species subject to an apparent high level of exploitation. The International Union for the Conservation of Nature (IUCN) lists this species as “Vulnerable” globally, and “Endangered” within western North Atlantic and Gulf of Mexico waters due to an over 80% decline in this region, with no evidence of population recovery. The extensive exploitation of dusky sharks may partly be attributed to the high market value of its fins, but the contribution of individual dusky shark stocks to the fin markets is unknown. This knowledge would be helpful to detect if specific stocks are experiencing disproportionate levels of exploitation. Due to its susceptibility to overfishing, current dire conservation status and need for additional information on its population dynamics, we analyzed the genetic population structure and genetic diversity of the dusky shark (n = 421) across 11 globally distributed locations utilizing 10 nuclear microsatellite loci. The nuclear marker analyses support and extend previously published mitochondrial marker work, identifying a strong divergence among Atlantic and Indo-Pacific samples. Furthermore, nuclear marker results indicate the presence of five genetically discrete management units for dusky sharks, with significant genetic differentiation between the western North Atlantic, South African, and each of three Australian site collections (N, E and W coasts). Discovery of these nuclear microsatellite- defined, smaller geographic scale management units provides a basis for the assignment of market-derived fins to their population of origin with the use of genetic assignment techniques.
GRAY,TEAGEN; FOX, DEWAYNE; WETHERBEE, BRAD; BERNARD, ANDREA; SHIVJI, MAHMOOD. 2013.
(TG, AB, MS) Save Our Seas Shark Center USA and Guy Harvey Research Institute, Nova Southeastern University, Dania, FL, USA; (DF) Department of Agriculture and Natural Resources, Delaware State University, Dover, DE, USA; (BW) Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA
Effective population size and genetic diversity of a species of concern, the sand tiger shark (Carcharias taurus) in Delaware Bay, USA
Genetic assessments can provide a conservation and management relevant perspective on the status of imperiled species including sand tigers, (Carcharias taurus). Sand tigers within the western North Atlantic were listed as a Species of Concern and thus prohibited from recreational and commercial fisheries in 1997 by the National Marine Fisheries Service. A previous global population study of sand tigers revealed the genetic isolation of individuals inhabiting the western North Atlantic from the remainder of this species’ distribution. Here, we assess the genetic status, including effective population size and genetic diversity of sand tigers from an area of known high abundance: Delaware Bay (n=557). Eleven species-specific microsatellite markers were used to analyze temporal variation in effective population size and genetic diversity of sand tigers collected from 2007-2012. Total length was used to back-calculate age estimates for each sex using data from a previous age and growth study on sand tigers within this region. Individual sharks of similar estimated age were grouped together to form year classes. Preliminary results indicate little genetic differentiation among year classes with respect to genetic diversity and effective population size, suggesting relatively stable, recent temporal population dynamics for Delaware Bay sand tigers. Estimates of genetic diversity (allelic richness) of sand tigers captured within Delaware Bay were greater than the previous survey within the western North Atlantic, suggestive of recovery in this previously exploited population.
GRUBBS, R. DEAN; FISHER, ROBERT. 2013.
(RDG) Florida State University Coastal and Marine Lab, St. Teresa, Florida, USA; (RF) Virginia Institute of Marine Science, Gloucester Point, Virginia, USA
A review of the life history of the cownose ray, Rhinoptera bonasus: Is a directed fishery sustainable?
Cownose rays (Rhinopteridae) are large, coastal batoids that migrate in very large schools and they are conspicuous predators on invertebrates where they occur. Their diets are varied, consisting primarily of relatively weak-shelled mollusks and crustaceans. However, predation on bivalves of commercial importance has drawn the ire of commercial fishers for more than two centuries. Along the East Coast of the U.S. there have been calls to develop fisheries for cownose rays since the 1970s, but the absence of viable markets limited development. Recently, highly publicized but weakly supported claims that dramatic increases in cownose ray populations, mediated by declines in shark populations, led to collapses in commercial bivalve stocks have renewed fishery development efforts and generated significant public support for cownose ray fisheries. An unregulated fishery for cownose rays, accompanied by a marketing campaign, has operated in Chesapeake Bay since 2007. Based on ~700 cownose rays collected from Chesapeake Bay, we estimated the age at maturity is 6-7 years for males and 7-8 years for females. Cownose rays grow rapidly during the first year of life resulting in relatively high growth coefficients (males, k=0.2741; females, k=0.1931). The maximum age observed was 21 years. Cownose ray fecundity is among the lowest of all vertebrates. Females typically produce one offspring following a gestation of eleven months, suggesting lifetime fecundity is 10-15, roughly an order of magnitude lower than most large elasmobranchs. These life history characters suggest cownose rays may be highly susceptible to over exploitation and developing fisheries should be monitored closely.
GUTTRIDGE, TRISTAN; BASS, NATHAN; WISZNIEEWSKI, JOANNA; GRUBER, SAMUEL; BROWN, CULUM. 2013.
(TG,CB) Cardiff University, Cardiff, UK; (SG) University of Miami, Florida, USA; (NB) Macquarie University, NSW, Australia; (JW) Taronga Zoo, NSW, Australia
Novel Acoustic Technology for Studying the Social Behaviour of Free-Ranging Sharks by Recording Individual Interactions
Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (4 body lengths) of each other, but rarely when at 10 m distance. Field trials were conducted on 5 juvenile lemon sharks in Bimini, Bahamas implanted with receivers lasting 17 days and 2 adult Port Jackson sharks Heterodontus portusjacksoni in Jervis Bay, Australia with external receivers for 30 days. Association data were recorded successfully for both species and these data were analysed using social network theory. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the link between social behaviour and space use of marine animals.
HAMILTON, IAN; ABRAHAMAS, MARK; FLEMING, IAN; BROOKS, EDD. 2013.
Memorial University, St. John’s, Newfoundland, Canada
Examining the Parameters Affecting the Distribution of Juvenile Lemon Shark Populations in Mangrove Creek Systems
Lemon sharks use coastal inlets (creeks) as nursery habitats, with females entering these creeks in the spring to give birth to live young that spend their first years of life in these locations. While this phenomenon is well known, the mechanism by which females select such locations for their young is not. Given that lemon sharks are most vulnerable to predation at this stage, we reasoned that females are selecting nursery habitats in a way that integrates both predation risk and growth rate on their offspring. We thus undertook to quantify population differences among nurseries and assess how food availability and risk shape patterns of use. Seine nets were used to capture and tag juvenile lemon sharks and potential prey items, in 9 mangrove creeks in South Eleuthera, The Bahamas. Drum-lines were used as a means of ascertaining predator abundances outside of each system. The results indicate a strong relation between lemon shark and prey abundance, and a weaker one in relation to predator abundances. Given the philopatric nature of juveniles, our results suggest that adult females are making habitat selection decisions on the island scale. These results highlight the importance of mangrove creek ecosystem conservation both locally and regionally.
HARA, KOUJIROU; FURUMITSU, KEISUKE; YAMAGUCHI, ATSUKO. 2013.
Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Nagasaki, Nagasaki, Japan
Age, growth, and size at sexual maturity of Kwangtung skate Dipturus kwangtungensis in the East China Sea
Kwangtung skate Dipturus kwangtungensis is distributed along the Japanese coast and areas around the East China Sea, Yellow Sea, and South China Sea. This species has relatively high commercial value in Japan and is mainly caught by bottom trawl fisheries. Despite its commercial importance, the life history of kwangtung skate remains poorly understood. This study aimed to determine the age, growth, and sexual maturity of kwangtung skate. A total of 260 specimens (137 males and 123 females) were collected using trawl survey of a university training ship from April 2009 to September 2012. Age determination was conducted by vertebral centrum analysis; the vertebrae between the 20th and 25th were sectioned at a thickness of approximately 0.5 mm along the central longitudinal axis. Annual band pair deposition was determined by marginal increment analysis. The von Bertalanffy growth model was fitted to the observed length- at-age data for each sex (males, L∞ = 765.8, k = 0.11, t0 = -1.37; females, L∞ = 814.8, k = 0.10, t0 = -1.30). Parameter estimates suggested that females attain greater asymptotic total length than that by males. Further, growth until 6 years was similar in both sexes, but after 6 years, females tended to grow larger than males. The observed maximum ages were 13 years for males and 15 years for females. Size and age at 50% sexual maturity were 501 mm TL, 7.9 years for males, and 579 mm TL, 9.9 years for females.
HARRIS, LINDSAY; BEDORE, CHRISTINE; KAJIURA, STEPHEN. 2013.
(LH,SK) Florida Atlantic University, Boca Raton, Florida, USA; (CB) Duke University, Durham, North Carolina, USA
Electroreception in the obligate freshwater stingray, Potamotrygon motoro
Elasmobranch fishes (sharks, skates, and rays) use electroreception to detect environmental electric fields, particularly the minute bioelectric fields produced by potential prey. Conductivity (e.g. salinity) dictates how bioelectric fields propagate, and thus influences how they are detected and localized by predators. A single elasmobranch family (Potamotrygonidae) is composed of obligate freshwater (FW) stingrays endemic to the Amazon River. A strictly FW existence has imposed morphological adaptions on their electrosensory system due to life in a high impedance medium. Because their electrosensory morphology differs from their marine relatives, FW rays may demonstrate corresponding differences in behavioral sensitivity. Little work has investigated whether the reduced sensitivity reported is due to the electrical properties of the FW medium, or to a marine-tuned sensory system attempting to function in a high impedance FW environment. The objective of this study was to quantify behavioral sensitivity of the obligate FW stingray Potamotrygon motoro to prey- simulating electric fields. The voltages produced by common teleost prey of P. motoro were measured and replicated for behavioral trials. The maximum orientation distance to the dipole center for any ray was 10.62 cm, and the smallest voltage gradient detected was 0.05 mVcm-1. This sensitivity is five orders of magnitude less than marine batoids (skates and rays). A euryhaline batoid species with marine-type ampullary morphology demonstrated a reduced sensitivity in FW compared to seawater; the FW values were similar to P. motoro which suggests that the conductivity of the medium, more so than ampullary morphology, dictates sensitivity of the elasmobranch electrosensory system.
HOLLENSEAD, LISA; GRUBBS, R. DEAN; CARLSON, JOHN. BETHEA, DANA. 2013.
Lisa Hollensead1, R. Dean Grubbs1, John Carlson2, Dana Bethea2
(LH,RDG) Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA; (JC,DB) NOAA National Marine Fisheries, Panama City, FL, USA
Analysis of small scale and daily movement patterns of juvenile Pristis pectinata within a nursery habitat
Habitat use studies can be used to both investigate ecological and behavioral patterns of animals and serve as useful management tools for conservation planners. However, specific habitats essential to survival can be difficult to determine for highly mobile marine animals, especially when these species are rare. While critical habitat has been very broadly delineated for the endangered smalltooth sawfish (Pristis pectinata), essential fish habitat within the nursery has not been fully described. Telemetry methods were used to determine daily activity spaces and Rates of Movement (ROM) of juvenile P. pectinata in a nursery in southwest Florida. Seven animals ranging in size from 85 – 175 cm fork length were tagged in 2011. Activity spaces were quite small and ranged from 0.07 – 0.17 km2 using 95% Minimum Convex Polygons (MCP), 0.01 – 0.16 km2 based on 50% Kernel Density Estimates (KDE), and 0.08 – 0.68 km2 based on 95% (KDE). Average ROM ranged from 2.4 to 6.1 meters/min. Activity space and ROM reflected the morphology of the bay in which the animal was tracked such that fish in small bays had small activity spaces and ROM. Activity space decreased and ROM increased at night indicating possible foraging behavior at night. A home range (0.17 km2) was calculated for one animal. Daily asymptotes in space used were reached for all other tracks suggesting daily activity spaces were determined despite relatively short tracking durations. Comparisons of tracked animal locations and 100 random locations suggested there was selection for proximity to mangrove shoreline.
HUETER, ROBERT; TYMINSKI, JOHN; MORRIS, JOHN; BETANCOURT, CONSUELO AGUILAR. 2013.
(RH,JT,JM) The Center for Shark Research, Mote Marine Laboratory, Sarasota, Florida, USA; (CAB) Centro de Investigaciones Marinas, Universidad de La Habana, La Habana, Cuba
Horizontal and Vertical Movements of a Satellite-tagged Longfin Mako (Isurus paucus Guitart Manday, 1966) in the Northwestern Atlantic Ocean
The longfin mako (Isurus paucus) is a poorly known oceanic shark captured in pelagic longline fisheries throughout its cosmopolitan distribution. With fins of moderate quality and meat of low market value, bycatch of this species may be under-reported due to finning and discard at sea and misidentification as shortfin makos. For the first time for this species, a pop-up archival satellite tag (PSAT) was successfully deployed to document the longfin mako’s horizontal and vertical movements and habitat. A mature male (237 cm TL) was captured by pelagic longline in the northeastern Gulf of Mexico (GOM) and fitted with a 90-day PSAT. The shark’s Most Probable Track showed movements from the GOM to the Straits of Florida along the northwest coast of Cuba, through the Bahamas, and into the open Atlantic Ocean east of the Chesapeake Bay, an estimated total distance of 6,192 km requiring an average rate of horizontal movement of 69 km day-1. The shark demonstrated a diel pattern of vertical movement characterized by greater time in the mesopelagic zone during the day and a shift into epipelagic waters during the night. Depth and temperature ranges during the track were 6-952 m and 4.6-28.8° C, respectively. Extended periods in cold water were observed with 19.5% of the time spent in temperatures ≤12° C. On the northwestern coast of Cuba, the longfin mako is the second most abundant shark caught in nearshore pelagic fisheries. Our satellite tag data demonstrate the interconnectedness of U.S., Cuban and Bahamian waters for this species.
IMHOFF, JOHANNA; GRUBBS, DEAN. 2013.
Florida State University, Tallahassee, FL, USA
Mercury Contamination in Sandbar Shark Muscle: A Thirty Year Comparison
The presence of mercury, particularly methylmercury, is of concern in aquatic systems because it is a neurotoxin that damages the central nervous and endocrine systems in humans and wildlife, including fishes. Mercury can biomagnify in species occupying high trophic levels and cause severe neurological and reproductive problems, including birth defects, in animals that consume these taxa. There is interest in understanding patterns of mercury contamination of fishes on decadal time scales. Most studies focused on freshwater fishes and a few focused on marine teleost fishes. However, there have been no studies investigating changes in mercury contamination of any shark species over multiple decades. Sandbar shark (Carcharhinus plumbeus) muscle tissue and embryos were collected from nearshore Hawaiian waters in the early 2000s to compare with published data from samples collected in the early 1970s, presenting a unique opportunity to investigate changes in mercury contamination over a thirty year period. Data on litter sizes and rates of stillborn shark pups were also collected. Average litter sizes in the early 2000s were similar to average litter sizes in the early 1970s (5.5 and 5.68, respectively), but rates of observed stillbirth increased from 2.2% of litters and 0.04% of embryos in the 1970s to 26.1% of litters and 5.3% of embryos in the 2000s. Quantification of mercury in tissues of stillborn shark pups and their mothers may provide insight as to why the rate of stillborn sandbar sharks in the early 2000s was higher than that in the early 1970s.
JAMES, KELSEY; EBERT, DAVID; BIZZARO, JOSEPH. 2013.
Kelsey James1, David Ebert1, Joseph Bizzarro2
(KJ,DE) Moss Landing Marine Laboratories, Moss Landing, CA, USA; (JB) University of Washington, Seatlle, WA, USA
Reproductive biology of a central California skate assemblage
Skates are subject to targeted and incidental fishing pressures worldwide, but most species have limited life history data available to help elucidate their population status. Additionally, skate landings are at best unreliable since they are rarely sorted to individual species, thus prohibiting accurate estimation of species-specific fisheries impacts. To remedy the lack of available data for eastern North Pacific skates we have systematically researched the life histories of 18 skate populations in this region. Here we report on the reproductive biology of four common central California rajid species: Beringraja binoculata, Raja inornata, R. rhina, and R. stellulata. Specimens were collected from 2002 to 2005 during trawl and longline surveys conducted in Monterey Bay by NOAA Fisheries. Total length (TL) at 50% maturity for females was estimated at 126.6 cm, 57.8 cm, 93.1 cm, and 63.1 cm for B. binoculata, R. inornata, R. rhina, and R. stellulata. Total length at 50% maturity for males was estimated at 100.5 cm, 50.1 cm, 83.0 cm, and 60.3 cm respectively. Females attained 50% maturity at 75% to 86% of the maximum TL, while males attained 50% maturity at 72% to 79% of the maximum TL. None of the species exhibited sex, size, or maturity segregation by depth. The maturity estimates and depth distribution of these species provides important insight into population dynamics of the central California skate assemblage.
KACEV, DAVID; HYDE, JOHN; BOHONAK, ANDREW; LEWISON, REBECCA. 2013.
(DK,AB,RL) San Diego State University, San Diego, CA, USA; (JH) Southwest Fisheries Science Center, La Jolla, CA, USA
Using genetics to better understand management of a data-poor, highly migratory predator
Short fin mako sharks (Isurus oxyrinchus) are highly migratory predators that are caught in recreational, commercial, and artisanal fisheries. Tagging studies in the Southern California Bight (SCB) suggest that makos can easily cross the US/ Mexico border, leaving them susceptible to fisheries in both countries. A better understanding of the population structure of mako sharks in the SCB is necessary to design appropriate binational management for the species. To address this issue we use 13 microsatellite markers to determine if there are barriers to gene flow within the bight. We use population simulations with parameter estimates based on empirical data to determine what levels of migration and population size can lead to our observed values for Fst and its analogues. We also use the molecular data to determine whether mako sharks in the region have a strict two or three year breeding cycle. To do this, we estimated the year of birth for each individual using length-based aging and year of capture and split the data set into birth year classes. We then tested for genetic variation between/among birth year classes.
KAJIURA, STEPHEN; HWANG, MIN SIG; BERQUIST, RACHEL; MEREDITH, TRICIA; BLACKBAND, STEPHEN; FRANK, LAWRENCE. 2013.
(SK) Florida Atlantic University, Boca Raton, FL, USA; (MSH,SB) University of Florida, Gainesville, FL, USA; (RB,LF) University of California San Diego, La Jolla, CA, USA; ™ University of Miami, Miami, FL, USA
Novel Olfactory System Neural Organization Revealed by Diffusion Tensor MRM
All life on earth exhibits some degree of chemical sensitivity. Within the vertebrate clade, the organization of the olfactory system is largely conserved, despite their morphological diversity. Histological evidence suggests that the elasmobranch fishes (sharks, skates, rays) demonstrate a remarkably different olfactory bulb organization than other vertebrates, including the teleost fishes. However, conventional histology is laborious, destroys intact structure, results in disjointed samples which must be reconstituted to elucidate three dimensional organization, and thus is inherently prone to tissue damage and registration errors. Here we show that Diffusion Tensor Microscopy (DTM) can be applied to facilitate Fiber Tract Mapping (FTM) of complex peripheral and central neural pathways. Using this non-invasive 3D digital imaging methodology, we found that elasmobranchs possess a novel, somatotopic organization of fiber tracts within the olfactory bulb. Elasmobranch olfactory receptor neurons maintain their spatial integrity within the bulb by remaining within one to two lamella widths of their point of origin, producing a somatotopic bulbar organization. This contrasts with teleost fishes which possess a chemotopic organization whereby olfactory receptor neurons that share similar chemical sensitivity converge in glomeruli regardless of their point of origin within the olfactory epithelium. Our results illustrate the utility of DTM and FTM to efficiently inform us about intact neuronal structure by revealing a three dimensional bulbar organization that we believe may be fundamentally different from all other vertebrates.
KEMPSTER, RYAN; HART, NATHAN; COLLIN, SHAUN. 2013.
University of Western Australia, WA, Australia
Survival of the Stillest: Predator Avoidance in Shark Embryos
Sharks use highly sensitive electroreceptors to detect the electric fields emitted by potential prey. However, it is not known whether prey animals are able to modulate their own bioelectrical signals to reduce predation risk. Here, we show that some shark (Chiloscyllium punctatum) embryos can detect predator-mimicking electric fields and respond by ceasing their respiratory gill movements. Despite being confined to the small space within the egg case, where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response. Knowledge of such behaviours, may inform the development of effective shark repellents.
KESSEL, STEVEN; HUSSEY, NIGEL; PETERSEN, STEPHEN; HIGDON, JEFF; DARWENT, JOHN; LANGE, HANS; FISK, AARON. 2013.
(SK,NH,AF) University of Windsor, Windsor, ON, Canada; (SP) Assiniboine Park Zoo, Winnipeg, MB, Canada; (JH) Higdon Wildlife Consulting, Winnipeg, MB, Canada; (JD) University of California Davis, Davis, CA, USA; (HL) Greenland National Museum and Archives, Nuuk, Greenland
Shallow water scavenging on marine mammals observed in a deep-water Arctic predator species, the Greenland shark (Somniosus microcephalus)
The Greenland shark is considered an important deep-water predator in the Arctic environment. Although the ecology of the species remains relatively unknown, diet data indicates feeding on a diverse prey base, with the presence of marine mammals commonly reported. The lethargic nature of this species evidenced by its extremely slow swimming speeds has raised questions on the mode by which they obtain large mammal prey, whether through predation events or by scavenging. The occurrence of both decaying and fresh seal/decapods remains have been observed in stomachs.
Despite their classification as a deep water shark species, anecdotal Inuit accounts of Greenland sharks entering shallow near-shore waters, in response to marine mammal hunts, are common place throughout the Arctic region. However, documented accounts of this scavenging behavior have previously been lacking. Following a first report by Beck and Mansfield (1969) on Greenland shark occurrence in shallow Arctic waters, we present three new sightings of Greenland sharks feeding on marine mammal carcasses in shallow waters in the Canadian Arctic (n = 2) and Greenland (n = 1). These data provide the first photographically documented behavior of the feeding of Greenland sharks on large mammal carcasses, a behavior only previously inferred from wounds.
In addition, preliminary long-line catch data are presented to link the presence of Greenland sharks with marine mammal movements/migrations. We suggest that Greenland sharks may actively track the movements of marine mammals and discuss the potential importance of this predator-prey interaction in current and historical contexts.
KILFOIL, JAMES; WETHERBEE, BRAD; CARLSON, JOHN; FOX, DEWAYNE. 2013.
(JK,DF) Delaware State University, Dover, DE, USA; (BW) University of Rhode Island, Kingstown, RI, USA; (JC) NMFS, SEFSC-Panama City Laboratory, Panama City Beach, FL, USA
Assessment of shore based angling on sand tiger behavior: Implications for recovery
In 1997 sand tigers, Carcharias taurus, were designated a Species of Concern by NOAA- NMFS due to life history characteristics and population declines. Despite protections, a recreational fishery targeting sand tigers has recently developed in the mid-Atlantic. Working with volunteer anglers, 25 sand tigers (mean 200cm FL; range 146-248cm FL) were captured via rod-and-reel and fitted with external acoustic VEMCO Ltd tags during July and August of 2012. The majority (52%) of shore-caught sand tigers were hooked posterior to the jaw, a factor often associated with increased mortality. Utilizing passive acoustic receivers we were able to characterize the behavior of shore-caught sand tigers and compare their movements to longline captured individuals tagged in previous years (n=71). We documented one probable post-release mortality among the recreational landed sand tigers. While initial estimates of post-release survival appear high, we have not yet been able to assess possible long term consequences. Given sand tigers’ low reproductive output and rebound potential, the magnitude and duration of the shore-based fishery may have deleterious effects on recovery. Furthermore, the majority of detections for both recreational caught sand tigers and those captured on longlines occurred in a centralized open ocean beach environment. This coupled with the relatively small center of activity for sharks in the study suggests that sand tigers occupy specific habitats within near shore coastal waters. If recovery efforts are to be successful managers must focus on ways to curb this emerging fishery, while also considering the potential long-term effects of coastal development on key habitats.
KNUCKEY, JAMES; EBERT, DAVID. 2013.
Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, California, USA
Phylogenetic Relationships of Eastern North Pacific Soft-Nosed Skates (Arhynchobatidae: Bathyraja)
The genus Bathyraja Ishihara is one of the most specious genera of skates, with approximately 48 species recognized globally. In the eastern North Pacific Ocean, bathyrajid skates range from the eastern Bering Sea to at least northern Baja California, Mexico. Like other members of the group, they are placed by local fishery agencies into a generic category, e.g. “skates.” Unresolved taxonomic issues abound within the genus, including the possible presence of cryptic species, species complexes, and taxonomic problems. Therefore, using the mitochondrial NADH dehydrogenase subunit 2 (NADH2) gene, we examined five of the species that occur within this region to analyze their phylogenetic relationships. These species include: B. abyssicola, B. aleutica, B. kincaidii, B. microtrachys, and B. trachura. Genetic differences were found among the bathyrajid species studied. Further data analysis, including the incorporation of morphological measurements and skeletal anatomy will provide further insight into the phylogeny of this skate genus. This information is useful for future studies exploring the diversity within Bathyraja, as well as providing important species identity information for fisheries management.
KOLMANN, MATTHEW; HUBER, DANIEL; DEAN, MASON; GRUBBS, DEAN. 2013.
(MK) University of Toronto, Toronto, Ontario, Canada; (DH) University of Tampa, Tampa, Florida, USA; (MD) Max Planck Institute, Berlin, Germany; (DG) Florida State University Coastal and Marine Laboratory, St. Teresa, Florida, USA
Ecomorphology of Durophagy in Myliobatiform Rays – Muscle Anatomy and Feeding Performance
The morphological and performance specializations demanded by a diet including hard, durable-shelled prey typically arise from more generalist ancestral bauplan. As a result, examinations of the routes by which durophagous characters arise – through phylogeny, ontogeny or phenotypic plasticity – can provide insight into how the specialized durophagous niche evolves and is maintained. We present data characterizing broad- scale differences in gross muscular anatomy between durophagous (myliobatid and rhinopterid) stingrays and their non-durophagous relatives, and then focus on the Rhinoptera bonasus species complex to examine the ecomorphological consequences of ontogenetic changes in feeding performance by relating modeled and measured bite forces to the fracture forces required to crush prey. We preliminarily extend our assumptions from the cownose ray model to other taxa, durophagous and piscivorous species alike, in order to explore feeding performance across disparate stingray morphologies, and discuss the importance of differences in muscle physiology across species, within species (i.e. phenotypic plasticity) and within individuals (e.g. comparing musculature from different body regions). Finally, we examine trends in feeding performance across durophagous chondrichthyans and discuss potential caveats against generalizing between batoid and shark systems.
KROETZ, ANDREA; POWERS, SEAN. 2013.
(AK,SP) University of South Alabama, Mobile, AL, USA; (AK,SP) Dauphin Island Sea Lab, Dauphin Island, AL, USA
Eating Between the Lines: Bonnetheads (Sphyrna tiburo) Show a Non- Traditional Functional Feeding Response
Large mobile predators can have strong influences in the structuring of marine food webs. Few quantitative estimates of the effects of predation by large mobile predators exist but are necessary to evaluate their impact on benthic prey species. A predator’s functional response provides quantitative information on the potential for predators to regulate local prey populations and community structure. We examined the functional response of the bonnethead (Sphyrna tiburo) to one of its few natural prey items brown shrimp (Farfantepenaeus aztecus). We simulated natural conditions in outdoor mesocosms and offered live prey at varying densities to quantify the functional response of this small coastal shark. Bonnetheads did not display a distinctive type of functional response; rather, they exhibited a response that fell between a type I and type II functional response. Bonnethead proportional consumption of brown shrimp remained relatively constant over all prey densities. Our results suggest that bonnetheads display what most closely represents a type I functional response. As an alternative to strict typing of predator functional response, we suggest that functional response be viewed as a continuum in order to achieve a more accurate depiction of how predation rates change as a function of prey densities.
LEARY, ARIANNE; GELSLEICHTER, JIM; GRUBBS, DEAN. 2013.
(AL,JG) University of North Florida, Jacksonville, FL, USA; (DG) Florida State University Coastal and Marine Lab, St. Teresa, FL, USA
Polycyclic Aromatic Hydrocarbon Biomarker Exposure in Elasmobranchs after the Deepwater Horizon Oil Spill: Investigations on the Smooth Dogfish, Mustelus canis
The Deepwater Horizon Oil Spill (DHOS) released large quantities of liquid petroleum into the Gulf of Mexico. 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. Prior research suggested the possibility of high PAH exposure in some coastal sharks, particularly the smooth dogfish, Mustelus canis. Therefore, the goal of this follow-up study was to evaluate PAH exposure and effects in this species as a result of the DHOS. This study evaluated PAH biomarkers such as Phase I and II detoxification enzymes and the presence and concentrations PAH metabolites in bile. Individuals of this species were collected from both oiled and un- oiled areas on Florida’s coast and compared. In addition, some pregnant Mustelus canis mothers and developing embryos were evaluated to examine the potential for maternal- fetal transfer of PAHs. We hypothesized that higher biomarker levels would be observed in northeast Gulf M. canis in comparison with conspecifics from unoiled locations as well as other elasmobranch species in the northeast Gulf. Additionally we anticipated temporal trends would be observed with biomarker levels declining as time from the spill lapsed.
LUER, CARL; WALSH, CATHY; BENNET, COURTNEY; WYFFELS, JENNIFER; EDSBERG, LAURA. 2013.
(CL,CW,CB) Mote Marine Laboratory, Sarasota, FL 34236, USA; (JW,LE) Daemen College Center for Wound Healing Research, Amherst, NY 14226, USA
Experimental Wounding and Preliminary Characterization of the Healing Response in the Atlantic Stingray, Dasyatis Sabina
Wounds are commonly observed in elasmobranch fishes, yet evidence of infection, necrotic tissue and keloid scarring are notably absent. The protective secretion produced by epidermal mucus cells in Atlantic stingrays (Dasyatis sabina) is being investigated to identify mucus-associated antimicrobial compounds and their potential role in the infection-free healing of wounds. Circular wounds 1.0 cm in diameter were inflicted, penetrating the epidermal and dermal layers of the skin, and exposing the underlying epaxial musculature. At regular intervals, digital photographs were taken to document the gross physical changes associated with the progression of wound healing. In all experimental wounding studies to date, infection-free healing in the form of scar tissue across the wound is effectively complete in approximately six weeks. With visual inspection and digital photography, a remarkably consistent observation is the appearance of slightly raised fibrous tissue in the center of wounds after approximately three weeks of healing which gradually flattens and spreads to the wound margins, forming uniform scar tissue across the wound. Preliminary histological examination of biopsied wounds and surrounding tissue after eight weeks of healing indicates that the wound epidermis remains distinct from the unwounded skin with respect to its pigmentation and allows the wound margin to be identified in the fixed tissue and prepared histological sections. While the wound is not fully restructured with pigmented cells, mucus cells are abundant in the hypertrophied epidermis. Wound studies designed to characterize histological changes and healing biomarkers associated with the formation and dissipation of the centralized fibrous tissue are underway.
LUCIFORA, LUIS; BARBINI, SANTIAGO; DI GIÁCOMO, EDGARDO; WAESSLE, JUAN; FIGUEROA, DANIEL. 2013.
(LL) Instituto de Biología Subtropical – Iguazú, Universidad Nacional de Misiones, Puerto Iguazú, Argentina; (SB) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; (DF) Laboratorio de Ictiología, Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina; (EDG) Grupo CONDROS, Instituto de Biología Marina y Pesquera “Alte. Storni”, San Antonio Oeste, Argentina; (JW) Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina
Estimating the geographic range of a threatened shark in a data-poor region: Cetorhinus maximus in the South Atlantic Ocean
The basking shark, Cetorhinus maximus, is widely distributed in temperate regions of all oceans except the Indian Ocean. In the southern hemisphere there is a large gap in the information on distribution, especially in the South Atlantic. We compiled all the records of basking sharks in the South Atlantic and used them in a recently developed tool for estimating geographic ranges of species, maximum-entropy distribution modelling (MaxEnt). Basking sharks records used in this study came from different sources: for the southwest Atlantic from scientific literature providing occurrence data, and the database of Onboard Fishery Observers Program of the Instituto Nacional de Investigación y Desarrollo Pesquero (Argentina); for the southeast Atlantic, the data came from the databases of the Fish Collection and the Shark Collection of the Iziko South African Museum, accessed from http://www.gbif.org/. Environmental data used as predictors were obtained from the Bio-Oracle database. Occurrence and environmental data were used in MaxEnt models. The model that best fit the data included four variables: chlorophyll minimum concentration, dissolved oxygen concentration, salinity, and sea surface temperature range. Our results indicated that basking sharks inhabit temperate to subtropical continental shelf waters. In the southeast Atlantic, basking sharks inhabited the cool waters from off southern South Africa to northern Namibia, and were absent in the subtropical waters off KwaZulu-Natal (South Africa). In the southwest Atlantic, basking sharks occurred on continental shelves from off Tierra del Fuego (Argentina) to off Rio de Janeiro (Brazil), being absent from waters north of Rio de Janeiro.
LYONS, KADY; LOWE, CHRISTOPHER. 2013.
California State University, Long Beach, CA, USA
Quantification of Maternal Offloading of Organic Contaminants in a Histotrophic Elasmobranch the Round Stingray (Urobatis halleri)
Maternal offloading is one route by which animals may bioaccumulate persistent organic pollutants, such as DDT and PCBs. However, this process has not been well documented in elasmobranchs, despite the important roles they play in maintaining communities. The round stingray (Urobatis halleri) represents a good model to examine maternal offloading processes due to their high local abundance and use of contaminated nearshore systems. Ovulated and near-term pregnant female stingrays were sampled from several local estuaries in southern California and organic contaminants were measured in the ova and embryonic tissues and compared to levels measured in corresponding female livers to determine route of and extent of transfer. Total organic contaminant loads measured in ovulated eggs were significantly lower than levels measured in embryos (132.84 ± 58.23 ng/egg versus 438.66 ± 301.64 ng/embryo; p < 0.001) indicating females have the ability to transfer contaminants throughout pregnancy. In addition, contaminant loads measured in pups showed a positive relationship with female contaminant concentrations (p < 0.001). However, females offloaded relatively low percentages of their total contaminant loads (1.5 ± 1.7%) compared to other species. Therefore, variation in reproductive modes utilized by elasmobranchs will likely influence the extent to which females may maternally offload contaminants.
MCCALLISTER, MICHAEL; GELSLEICHTER, JIM. 2013.
University of North Florida, Jacksonville, FL, USA
Identifying a Scalloped Hammerhead Nursery in the Inshore Waters of NE Florida
Scalloped hammerheads (Spyrna lewini) are a large shark common in the coastal waters of the eastern U.S. It is well documented that juvenile scalloped hammerheads utilize shallow nearshore waters as nursery habitat; however, few studies have identified potential nursery habitat in Florida. With the National Marine Fisheries Service recently listing the scalloped hammerhead as overfished, and Florida Fish and Wildlife’s decision to prohibit commercial and recreational harvest of scalloped hammerheads, identifying scalloped hammerhead nursery habitat in Florida waters is critical to helping protect this species. This study identifies a nursery for young-of-the-year scalloped hammerheads in the Tolomato River, FL. Sampling occurred from May – October from 2010-2012, and a total of 123 YOY scalloped hammerheads were caught. Scalloped hammerheads had a mean length of 49.0cm TL (range = 39.5 – 59cm TL), and all had well healed umbilical scars. Mean CPUE was greatest in July (3.5 sharks/50 hooks * hr). There was a significant difference in the observed sex ratio of males to females (1.56:1, χ2 = 5.3, p = 0.017). Only 3 tagged sharks were recaptured, two of which were re-caught less than 1km from where they were tagged. Annual mean CPUE was significantly greater in the Tolomato River (2.4 sharks/50 hooks *hr) compared to surrounding areas in Cumberland (0.08 sharks/50 hooks *hr) and Nassau (0.04 sharks/50 hooks *hrs). These findings suggest this area functions as nursery habitat for this species, and is only the second documented account of a scalloped hammerhead nursery on the east coast of Florida.
MCDOWELL, JAN; BRIGHTMAN, HEIDI; FISHER, ROBERT. 2013.
Virginia Institute of Marine Science, Gloucester Point, VA, USA
Species Boundaries and Cryptic Species in Atlantic Rhinopterids: Will the Real R. bonasus Please Stand Up?
The family Rhinopteridae contains a single genus, Rhinoptera, which includes 8 recognized species. The lack of obvious morphological characters to discriminate these species complicates accurate identifications. The cownose ray, Rhinoptera bonasus, ranges from southern New England to southern Brazil within the western Atlantic Ocean and throughout the Gulf of Mexico and off Cuba. Claims of increases in the population growth rate of the cownose ray coupled with concerns over damage to shellfish culture, grow-out, and restoration operations have led to pressure for a targeted fishery in regions such as Chesapeake Bay, Virginia, despite the fact that no investigation of genetic stock structure has been conducted. We present preliminary data based on analysis of mitochondrial and nuclear DNA markers indicating that there are at least two cryptic species of Rhinoptera in the eastern Gulf of Mexico, the cownose ray and a second species which bears a close genetic affinity to the Ticon cownose ray, R. brasiliensis, which is considered to be endemic to Brazil. The genetic data also suggests that there has been historical introgression between these two species. We have not seen evidence of multiple species off the Atlantic coast based on limited sampling effort. Furthermore, analysis of a limited number of cownose ray samples captured off the coast of Campeche, Mexico suggest that the Caribbean Sea may harbor a separate genetic stock. This study highlights the need for a comprehensive assessment of both species boundaries and stock structure in Atlantic Rhinopterids.
MORALES, MILLKE JASMINE ARMININI; OLIVIERA, CALUDIO; MENDONÇA, FERNANDO FERNANDES; COELHO, RUI; SANTOS, MIGUEL NEVES; FAUSTO, FORESTI.
(MJAM,CO,FFM,FF) Instituto de Biociências, UNESP, Botucatu, São Paulo, Brazil; (RC) Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Faro, Algarve, Portugal; (FF) Instituto Português do Mar e da Atmosfera (IPMA, I.P.), Olhão, Algarve, Portugal
Population genetic structure of the bigeye thresher shark, Alopias superciliosus, using mitochondrial DNA control region, in a comparison between the Atlantic and Indian Oceans
The bigeye thresher shark, Alopias superciliosus, is a highly migratory species that occurs in oceanic and coastal areas of all Oceans, particularly in tropical regions. It is currently assessed as globally “Vulnerable” by the IUCN (International Union for the Conservation of Nature) because of its population declines in the past years. Considering the scarcity of information regarding the biology and population genetics of this species, the current study sought to characterize the genetic population structure of A. superciliosus, comparing samples from the Atlantic and Indian Oceans. Sequences of mitochondrial DNA from the control region (D-loop) were used, with 913 bp (base pairs) analyzed from 122 specimens from the Atlantic and 11 specimens from the Indian Ocean. Considering all the samples, both from the Atlantic and Indian Oceans, only eight haplotypes were found, with one of the haplotypes shared by 93.2% of the analyzed sharks. These results suggest a very low genetic variability (π = 0.00121 ± 0.00042 and h=0.131 ± 0.040), no population structure (no significant ΦST value), and an intense gene flow across the studied areas, even between the two Oceans. Therefore, for fisheries management and species conservation purposes, a single A. superciliosus stock should be considered in the entire sampled area, with this low genetic variability suggesting a natural fragility of the species. Furthermore, it seems the bigeye thresher sharks have the ability of migrating between those two regions of the Atlantic and the Indian Oceans.
NEFF, CHRISTOPHER; HUETER, ROBERT. 2013.
(CN) University of Sydney, Sydney, Australia; (RH) Center for Shark Research, Mote Marine Laboratory, Sarasota, FL, USA
The role of science in improving shark bite terminology
The terminology surrounding shark “attack” is outdated and misleading to the public, perpetuating a perception of universal, intent-laden fatal outcomes. In this paper we examine the role of science in shark “attack” terminology. For more than 300 years scientists have sought to explain why sharks bite humans, including the work
of Linnaeus (1758), Coppleson (1933), Gilbert (1963), Schultz (1963), Davies (1964), Baldrich (1974), Tricas and McCosker (1984), Gruber (1988) and Hazin and Burgess (2008). This paper builds off the typology of human-shark interactions proposed by Neff and Hueter (2013) and argues that communities such as the American Elasmobranch Society should consider adopting a formal position on the proper usage of “shark attack” terminology because: a) current terms fail to represent scientific knowledge; b) media discourse is misleading in its overuse of the term “shark attack”; and c) government policy overreactions to shark “attacks” threaten shark conservation of vulnerable species. This analysis provides a starting point for a robust scientific review of human-shark interactions. Given the attention of governments and the media to human-shark interactions, it is in the interest of the scientific community to call for the use of better, data-based terminology describing this phenomenon.
NEWBY, JENNIFER; SHEDLOCK, ANDREW. 2013.
College of Charleston, Charleston, SC, USA
An Assessment of Population Genetic and Social Structure in the Spotted Eagle Ray (Aetobatus narinari) off Sarasota, FL and the southeastern United States
The spotted eagle ray, Aetobatus narinari, is a semi-pelagic myliobatoid recognized as near-threatened by the World Conservation Union. A decreasing population trend, K- selected life history and primarily inshore, coastal habitat renders this species susceptible to over-exploitation by targeted fisheries, drift netting, and capture as bycatch. Recent molecular investigations and the subsequent taxonomic recognition of A. narinari as a species complex have revealed a complete absence of data concerning population structure and genetic health for this species in the Central Atlantic region. This study is the first to examine fine-scale structure on a regional basis in the Gulf of Mexico and coastal Atlantic waters off the U.S. Individuals sampled non-invasively from 4 sites; Sarasota (n=143), the Everglades (n=36), Ft. Pierce (n=8) and the southeast Atlantic (n=24), were genotyped across 8 microsatellite loci. Standard tests for Hardy- Weinberg Equilibrium, null alleles, linkage disequilibrium, allelic richness (mean= 15.38) and gene diversity (0.7014) were performed. Analyses of statistically significant patterns of geographic structure using the applications STRUCTURE and AMOVA available in the Arlequin v. 3.5 software package yielded non-significant findings and support a single population model opposed to several admixed populations. Similarly, tests for isolation by distance returned non-significant results (Mantel test, p=0.605). Effective population size was estimated between 2,200 and 3,300 (LDNe and ONeSAMP applications, respectively). These assessments of population structure and measurements of genetic health for the Central Atlantic provide a critical first step toward furthering our understanding of A. narinari vitality and better informing conservation and management decisions.
NOSAL, ANDREW; KEENAN, ELIZABETH; GNEEZY, AYELET. 2013.
(AN) Scripps Institution of Oceanography, University of California – San Diego, La Jolla, CA, USA; (EK,AG) Rady School of Management, University of California – San Diego, La Jolla, CA, USA
Happy and Playful Sharks? The Effect of Background Music in Nature Documentaries on Viewers’ Perception of and Willingness to Protect Sharks
To examine the effect of background music on viewers’ perception of and willingness to protect sharks, undergraduate students were randomly assigned to view a two-minute documentary montage of swimming sharks set to “happy” music (n=37), “scary” music (n=39), or silence (n=36). Participants then rated how well (1 = not at all, 7 = very well) each of six adjectives (scary, dangerous, playful, happy, beautiful, intelligent) described the sharks. Control participants (silent condition) rated sharks neutrally (mean rating not significantly different from 4.0) for scary (3.8) and dangerous (3.8). However, participants in the scary condition rated sharks significantly more scary and dangerous (5.2 and 5.1, respectively), while participants in the happy condition rated sharks significantly less so (2.9 and 3.1, respectively). Similarly, control participants rated sharks neutrally for playful (3.5) and happy (3.8). However, participants in the happy condition rated sharks significantly more playful and happy (4.4 and 4.9, respectively), while participants in the scary condition rated sharks significantly less so (2.4 and 2.6, respectively). Music treatment did not affect ratings for beautiful and intelligent. Finally, participants were given the option to donate part of their US$2.00 earnings to a shark conservation charity.
Mean donation was highest in the happy condition (US$1.30), compared to scary (US$0.93) and silent conditions (US$0.92). Additional studies are underway to examine the effects of other music treatments on perception of and willingness to protect sharks, including support for banning shark fins in restaurants and listing the white shark (Carcharodon carcharias) as an endangered species in California.
PEREZ, JUAN CARLOS. 2013.
El Colegio de la Frontera Sur, Lerma, Campeche, Mexico
The Reproductive Cycle of the Cownose Ray Rhinoptera bonasus in Southern Gulf of Mexico: it Can be Biennial?
The cownose ray Rhinoptera bonasus is one of the most abundant batoid species in southern Gulf of Mexico, where represents a significant component of the by-catch in the target fishery for the spotted eagle ray Aetobatus narinari in western Campeche Bank. Previous studies estimate an annual reproductive cycle for the cownose ray in north- western Atlantic and northern Gulf of Mexico; however, such studies lacks the information to support the concurrence between gestation and vitellogenesis. In this study, the analysis of 76 adult females with a size range of 88–106 cm disk width (DW) suggest that the female reproductive cycle is apparently biennial. The gestation lasts about 12 months, and the gestation and vitellogenesis are consecutive (gravid females containing full term embryos, > 34 cm DW, had small non-vitellogenic oocytes, < 18 mm diameter). Alternative hypothesis are analyzed and discussed (biannual and annual reproductive cycles) in order to support the estimation of the biennial reproductive cycle.
PEREZ, JUAN CARLOS; CUEVAS, ELIZABETH; MENDEZ, IVAN; CU, NICTE. 2013.
El Colegio de la Frontera Sur, Lerma, Campeche, Mexico
The Small-Scale Target Fishery for Spotted Eagle Ray Aetobatus narinari in Southern Gulf of Mexico: Considerations for Management
The spotted eagle ray Aetobatus narinari is listed as Near Threatened by the IUCN red list. A target fishery for this species is carried out since about 150 years in Southern Gulf of Mexico. Fishery data collected since 2009 indicates that the spotted eagle ray is seasonally target by at least 30 small-scale out-board motored boats (7.7 m long) with gill-nets made of silk (mesh size of 30.5-36.5 cm) in a fishing area of 8-50 km off the coast of the states of Campeche and Yucatán. The catch is composed by juvenile of both sexes and adult males, and the overall size range for females was 54-202 cm DW and for males 44-150 cm DW. Catch rate varied from 3.0 to 6.6 rays per fishing trip, the highest catches occurred between November and March (during the winter cold front season), and large rays (>130 cm DW) are more commonly caught in fishing areas far from the shore (>20 km). There are no management strategies for this fishery in spite of according to fishermen catches have diminished in the last three decades. Fishermen do not require special license for this fishery and the Mexican Official Catch statistics lack the information of catch and effort for the fishery. Specific fishing license to participate in this fishery should be required and a logbook system by fishing boat should be encouraged in order to generate catch statistics to determine the trend of the catches and provide more elements for future specific fishery management strategies.
PETERSON, CHESTON; GRUBBS, DEAN. 2013.
(CP) Florida State University Department of Biological Sciences, Tallahassee, FL, USA; (DG) FSU Coastal and Marine Laboratory, St. Teresa, FL, USA
Sharks and Large Teleosts of Florida’s Big Bend: Abundance, Distribution, and Community Structure
The Florida Big Bend contains one of the world’s largest continuous seagrass beds. This 300 km stretch of coastline in the northeast Gulf of Mexico supports a high diversity of sharks and larger teleost fishes, but the community structure of these faunas are poorly described in the area to date. Data from spatially-balanced fishery-independent surveys employing experimental longlines and gillnets conducted from 2009 to 2012 were used to describe the shark and larger teleost assemblages along the Florida Big Bend. Species richness, diversity, and evenness were compared spatially over the survey area. Non- metric multidimensional scaling (NMDS) was used to explore species associations and to infer what environmental factors may influence the observed patterns of species distribution and abundance in the system. We found species assemblages were spatially variable and the northern portion of the Big Bend was more species rich and diverse. Environmental factors such as bottom profile (proxy for habitat complexity), depth, and salinity are correlated with the data structure found using NMDS, and these may be important when considering the influence of environmental parameters or habitat quality on spatially-variable catch data.
PFLEGER, MARIAH O.; GRUBBS, R. DEAN; DALY-ENGEL, TOBY S. 2013.
(MOP,TSD) University of West Florida, Pensacola, Florida, USA; (RDG) Florida State University, Tallahassee, Florida, USA
Dogfish Shark Speciation in 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. These sharks are easily misidentified due to the high degree of similarity with their congeners, and recent taxonomic research on this species from the Pacific has indicated that S. mitsukurii may in actuality comprise a species complex, a group of separate but closely related species. In an effort to understand the global taxonomy of the S. mitsukurii complex, we are using a combination of morphological evidence and genetic techniques to identify separate dogfish stocks throughout the Pacific and elsewhere. Thus far, preliminary data have indicated that Squalus cf mitsukurii from Hawaii is likely an isolated, distinct species. Using meristics as well as approximately 700 base pairs of mitochondrial DNA (barcode region), we will investigate this question in dogfishes from the Gulf of Mexico and West Atlantic. We hypothesize that due to geographic distance, Squalus cf mitsukurii in the Gulf of Mexico may also have become isolated from the type population in the West Pacific.
PICKARD, ALEXNADRIA; WETHERBEE, BRAD; VAUDO, JEREMY; NEMETH, RICHARD; KADISON, ELIZABETH; BLONDEAU, JEREMIAH; SHIVJI, MAHMOOD. 2013.
(AP,JV,MS) The Guy Harvey Research Institute, Oceanographic Center, Nova Southeastern University, Florida, USA; (BW) The Guy Harvey Research Institute, Nova Southeastern University and the University of Rhode Island, Florida, Rhode Island, USA; (RN,EK,JB) University of the Virgin Islands, St. Thomas, Virgin Islands, USA
Characterization of shark movements on a mesophotic Caribbean coral reef and temporal association with fish spawning aggregations
Little is known about the importance of mesophotic coral reefs as habitat for sharks. Since many fish species aggregate to spawn on mesophotic reefs, seasonal concentration of potential prey biomass may influence the use of these habitats by large sharks. We employed acoustic telemetry to examine the movements of three shark species (lemon shark, Negaprion brevirostris; tiger shark, Galeocerdo cuvier; and Caribbean reef shark, Carcharhinus perezi) to determine 1) whether there was a spatio-temporal relationship between sharks and grouper aggregations at two fish spawning aggregation (FSA) sites (Hind Bank and Grammanik Bank) along the southern reef shelf edge off St. Thomas, USVI, and 2) the comparative spatio-temporal patterns of mesophotic reef habitat use by the three shark species. Lemon sharks were present at the two FSA sites significantly more often during the grouper spawning (Dec-May) than non-spawning season (Jun- Nov) in each of the five years of monitoring (p=0.008), indicating orientation in relation to the presence of spawning grouper. In contrast, there was no relationship between the presence of tiger and Caribbean reef sharks at FSA sites and grouper spawning season. Tiger sharks occupied the largest activity space within the monitored array (887km2), closely followed by lemon sharks (863km2); Individuals were detected across nearly the entire area of the array. Caribbean reef sharks utilized a much smaller activity space within the monitored array (8km2), composed exclusively of mesophotic reef habitat located within FSA sites. This mesophotic reef serves as habitat to all three shark species with varying degrees of fidelity.
PORTNOY, DAVID; GIRESI, MELISSA; FRAZER, BRYAN; GOLD, JOHN. 2013.
(DP,MG,JG) Texas A&M University, College Station, TX, USA; (BF) South Carolina Department of Natural Resources, Charleston, SC, USA
Genetic Population Structure of the Finetooth Shark (Carcharhinus isodon) in the U.S. Atlantic
The finetooth, Carcharhinus isodon, is a small coastal shark found along the Atlantic coast of the southern United States and in the Gulf of Mexico. The presence of gravid females as well as neonate and juvenile finetooth sharks in estuarine and nearshore habitats of South Carolina and the Gulf coasts of Florida and Alabama suggest that these areas are nursery grounds. We assessed patterns of variation in 15 nuclear-encoded microsatellites and sequences of the entire mitochondrial (mtDNA) control region among samples collected from the three putative nursery sites. Analyses based on microsatellite alleles and genotypes revealed modest levels of variation within samples and significant heterogeneity among samples. By contrast, analyses of mtDNA sequences revealed low haplotype diversity within samples and homogeneity among samples. The results suggest that unlike in larger coastal carcharhinid sharks where females exhibit philopatry to nursery areas, both male and female finetooth sharks engage in reproductive migrations. In addition, the lack of congruence between marker types likely reflects historical demographic processes related to the Wisconsin glacial period, highlighting the difficulty inherent in using molecular markers to examine population structure in temperate/tropical species inhabiting coastal waters of the U.S.
POULAKIS, GREGG; GRIER, HARRY. 2013.
(GP) Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, Port Charlotte, FL, USA; (HG) Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, St. Petersburg, FL, USA
Reproductive Biology of the Cownose Ray (Rhinoptera bonasus) in the Charlotte Harbor Estuarine System, Florida
The cownose ray, Rhinoptera bonasus, is an abundant species in the western Atlantic, but its reproductive biology is not completely known because of the difficulty in obtaining year-round samples in large portions of its range where the species is migratory. To address this knowledge gap, cownose rays were studied in a subtropical estuarine system where individuals are available year-round. For females, based on ovary length and weight, maximum follicle diameter, and mating wounds and scars, the size at 50% maturity was 701 mm disk width (DW) and the size at 100% maturity was 712 mm DW. For males, based on clasper morphology, testis length and weight, and epididymis width, the size at 50% maturity was 681 mm DW and the size at 100% maturity was 712 mm DW. Overall testis size and mean testis lobe diameter peaked up to two months prior to ovary size and maximum follicle diameter, indicating that males were preparing to inseminate females during the entire parturition and mating period. Mating behaviors were observed mostly between April and June. Ovulation peaked in May, and parturition occurred primarily in March and April after an 11-12 month, single embryo, gestation period suggesting that females are synchronous in Charlotte Harbor. Size at birth was 202-383 mm DW. Concurrent vitellogenesis and gestation indicated a clearly defined annual reproductive cycle that may be completed within the estuary. Germinal epithelia were actively producing follicles in embryos, suggesting that folliculogenesis in Rhinoptera occurs primarily before parturition.
POULAKIS, GREGG; OLIN, JILL; STEVENS, PHILIP; DEANGELO, JACQUELYN; TIMMERS, AMY; GRUBBS, R. DEAN; FISK, AARON. 2013.
(GP,PS,JD,AT) Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute, Port Charlotte, FL, USA; (JO) Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, USA; (RDG) Florida State University Coastal and Marine Laboratory, St. Teresa, FL, USA; (AF) Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada
Use of Stable Isotopes to Infer Feeding Habits and Ontogenetic Diet Shifts by the Endangered Smalltooth Sawfish (Pristis pectinata), in Florida
The smalltooth sawfish, Pristis pectinata, is an endangered species in the western Atlantic Ocean. Little research had been conducted on this species prior to its protection under the Endangered Species Act in 2003. Since listing, research focused primarily on juveniles has provided insights into life history including habitat use during their first three years of life when they reside in estuarine nurseries. The goal of this study is to analyze the feeding biology of the smalltooth sawfish on a trophic-level scale. Our hypothesis is that neonates initially feed like other invertebrate specialist batoids when they still have their rostral sheath; then eventually switch to feeding like piscivorous sharks once the rostral sheath disappears and they become more experienced predators. To test this hypothesis, trends in stable isotopes of carbon (δ13C) and nitrogen (δ15N) from fin clips of sawfish, cownose rays, and bull sharks collected from the same nursery are being analyzed. These analyses are ongoing, but preliminary data suggest that an ontogenetic diet shift does occur from secondary consumer (diet composed primarily of invertebrates) to piscivore (diet composed primarily of estuarine fishes) during the first few months that juvenile sawfish are in the Charlotte Harbor nursery. Recent acquisition of samples from adult sawfish may indicate an additional dietary shift and provide insight on whether or not maternal physiology influences neonate isotopic signatures. Documenting ontogenetic diet shifts in this species may help explain the timing of changes in habitat use that have been observed during long-term acoustic studies.
POWERS, SEAN; DRYMON, MARCUS. 2013.
University of South Alabama, Mobile, AL, USA
Spatial and temporal patterns of predation by cownose rays determines source and sink locations in bay scallops populations
We examined the foraging behavior of cownose rays (Rhinoptera bonasus),which perform seasonal migrations along the U.S. Atlantic Coast and feed on hard-shelled prey, to determine their impact on local populations of bay scallops (Argopecten irradians) within North Carolina (USA) sounds. Observational data and experimental manipulations demonstrate that cownose rays selected feeding sites from among spatially discreet seagrass beds during their late summer/fall (southward) migration based on local density of bay scallops. Consequently, mortality of bay scallops during the brief two- week period of passage through the high-salinity sounds of North Carolina exhibited a density-dependent relationship best described by a Gompertz curve with a threshold value of 3 bay scallops per m2. Because this intense predation occurs prior to annual spawning of bay scallops, resulting in local densities below threshold levels potentially required for successful spawning and fertilization (i.e., Allee effects), local population sinks were created and, in some instances, maintained over multiple years. Bay scallop mortality during the spring (northward) cownose ray migration was low suggesting that cownose rays may not feed intensely in the sounds as they move north. Our results imply that migratory predators can greatly influence metapopulation population dynamics over large spatial scales via significant, even if pulsed, mortality.
PROHASKA, BIANCA; TSANG, PAUL; DRIGGERS, WILLIAM III; HOFFMAYER, ERIC; SULIKOWSKI, JAMES. 2013.
(BP,JS) University of New England, Biddeford, ME, USA; (PT) University of New Hampshire, Durham, NH, USA; (WD,EH) National Marine Fisheries Service, Pascagoula, MS, USA
Development of a Non-lethal, Minimally Invasive Protocol to Study Elasmobranch Reproduction
Currently, circulating levels of plasma steroid hormones are used as a non-lethal method to determine reproductive maturity and reproductive cycles in elasmobranchs. However, this method can prove problematic to perform on large and/or endangered species, because of difficulties involved with specimen handling. These constraints make it imperative for new techniques to be developed for studying the reproductive biology of elasmobranchs. Previous work conducted on other vertebrates has shown that steroid hormones can be successfully extracted from muscle tissue. The process of collecting muscle tissue samples is quick, minimally invasive, and may be conducted without removing the animal from the water, facilitating its use on larger, and/or endangered species of elasmobranchs. Thus, the objective of the current study was to develop a valid method for extracting steroid hormones from the skeletal muscle tissue of the lecithotrophic aplacental viviparous spiny dogfish (Squalus acanthias), the oviparous little skate (Leucoraja erinacea), and the placental viviparous Atlantic sharpnose shark (Rhizoprionodon terraenovae). The results suggest that concentrations of muscle progesterone [P4], testosterone [T], and estradiol [E2] can be successfully quantified to study reproduction by radioimmunoassay. Additionally, there were significant correlations between plasma and muscle [E2] concentrations in S. acanthias, as well as plasma and muscle [P4], [T] and [E2] concentrations in R. terraenovae and L. erinacea. The results of the present investigation demonstrated that skeletal muscle is a non-lethally harvested tissue that is well suited for studying the reproductive biology of elasmobranchs.
SHAW, ASHLEY; FRAZER, BRYAN; SANCHO, GORKA. 2013.
(AS,GS) College of Charleston, South Carolina, USA; (BF) South Carolina Department of Natural Resources, South Carolina, USA
Trophic Ecology of an Estuarine Predatory Fish Community in South Carolina Assessed by Stable Isotope Analysis
Estuaries serve as habitats and nurseries for many recreationally and commercially important fish species. Understanding the diet and trophic relationship dynamics of the fish populations within the estuarine community is essential to effectively managing these species. Upper-level predatory fish are among the most sought-after fisheries species, and studying the dietary niche overlap of this community can infer the probability of competition and niche partitioning within this highly productive ecosystem. In attempt to establish these trophic relationships, dietary niche overlap of the predator community in the Cape Romain National Wildlife Refuge (specifically Bulls Bay and its surrounding tidal creeks) were assessed using stable isotope analysis (d13C and (d15N) on 7 elasmobranch and 3 teleost species. Fish, collected via trammel nets, gillnets and longlines in the channels and along the banks of the estuary with cooperation of SCDNR, were measured, muscle biopsied from the dorsal musculature, and then released. Quantitative metrics indicate that these predators occupy different trophic levels and use different carbon sources. Dietary niche overlap shows that some elasmobranchs have unique isotopic niche spaces indicating potential resource partitioning, while several species of teleosts and sharks had varying degrees of overlap that implies shared resources. Bayesian stable isotope mixing models revealed information about the contribution of distinct carbon sources in each predators diet.
Results may have implications for ecosystem-based management of the Cape Romain estuarine system that can be applicable to other estuaries.
SHAW, ASHLEY; SANCHO, GORKA; NEER, JULIE A.. 2013.
(AS,GS) College of Charleston, Charleston, SC, USA; (JAN) SEDAR, North Charleston, SC, USA
Stable isotope analysis reveals resource partitioning in the cownose ray, Rhinoptera bonasus
Cownose rays are considered a mesopredator, and feed mainly on invertebrates, such as molluscs. Stable isotope analysis of a predatory community in a South Carolina estuary reveals a distinct diet from teleost and other elasmobranch predators, with no overlap in dietary niche. This data not only supports diet studies previously conducted on cownose rays, this unique dietary niche in isotopic space shows that these rays exhibit resource partitioning in this estuarine habitat. In addition, the small ranges of d13C and d15N values indicate diet specialization in the sampled population.
SHIFFMAN, DAVID; HAMMERSCHLAG, NEIL. 2013.
University of Miami, Miami, FL, USA
Use of Social Media to Assess the Knowledge and Attitudes of Different Stakeholder Groups Towards Shark Conservation, Including Implications for Public Support for Management Policies
Many large sharks have been experiencing varying levels of population declines at a global level, primarily due to overfishing. However, the scale, magnitude and geographic distribution of these declines across species remain uncertain. This is of particular importance given that predator declines have the potential to impact ecosystem structure and function through trophic cascades. This has raised growing concern among different stakeholder groups including scientists, wildlife managers, environmentalists and fisherman. Given the potential to influence both policy and public opinion, understanding the knowledge and attitudes of different stakeholders towards shark conservation issues have been identified as a research priority. In recent years, the rising use of social media has become among the most rapid, wide-spread and influential ways for both individuals and organizations to communicate their ideas to a diverse global audience. Shark conservation is one of the most actively discussed ocean issues and is discussed online by many thousands of users. Here we use large-scale content and discourse analyses of social media updates (primarily Facebook and twitter) shared with the public by representatives of different stakeholder groups public to assess their knowledge and attitudes towards the two of the primary issues in shark conservation, specifically the population status and ecosystem importance of sharks. Our results demonstrate that many of the arguments being made and disseminated by non-scientists advocates and organizations do not accurately represent available data. We discuss these results in terms of potential to impact policy decisions.
SOARES, MATEUS COSTA; CARVALHO, MARCELO REOGRIGUES. 2013.
Universidade de São Paulo, São Paulo/SP, Brazil
Comparative myology of the mandibular and hyoid arches in elasmobranchs (Chondrichthyes) and its relevance for phylogenetic hypotheses of living species
Past studies attempting to reveal the interrelationships of Elasmobranchii have proposed two principal hypotheses. Based on morphological data, elasmobranchs are divided into two groups, Galeomorphi and Squalomorphi, the latter including the rays (Batoidea; being part of the clade Hypnosqualea with Squatina and Pristiophoriformes). However, molecular data suggest that Galeomorphi and Squalomorphi form a monophyletic clade, sister-group to Batoidea (sharks are therefore monophyletic). To elucidate this conflict, the present work examined the comparative anatomy of jaw and hyoid arch muscles of about 100 species (37 families) of sharks, rays and chimaeras. Some 35 myological characters are proposed, based on our observations and information from the literature, which shed light on different aspects of elasmobranch intrarelationships. These concern, for example, the monophyly of Galeomorphi (e.g. presence of a tendon linking m. levator labii superioris to the neurocranium), the monophyly of Squalomorphi (e.g. presence of m. adductor mandibulae superficialis), relationship between Heterodontiformes and Orectolobiformes (e.g. variations in m. levator labii superioris and m. constrictor hyoideus dorsalis), the relationship between Chlamydoselachus and Hexanchidae, the monophyly of Squaliformes, the monophyly of Hypnosqualea (e.g. presence of m. depressor rostri and variations in m. spiracularis), and the intrarelationships among potamotrygonid stingrays (variations in adductor mandibulae complex and m. spiracularis). Muscle characters have great potential to help clarify relationships among living elasmobranch groups, and mandibular and hyoid arch muscles favor the morphological hypothesis in which batoids are nested within squalomorphs.
SPAET, JULIA; BERUMEN, MICHAEL. 2013.
King Abdullah University of Science and Technology, Thuwal, Makkah, Saudi Arabia
Long-term Market Survey of Saudi Arabian Red Sea Shark Fisheries
Shark populations worldwide are severely threatened due to overexploited and unregulated fisheries. Information on unmonitored coastal fisheries is difficult to obtain, especially in regions where historical data on shark diversity, abundance, or catch levels is sparse. Yet it is vital to develop an understanding of the historical changes determining population trends and evaluate the current status of shark populations in order to conserve these vulnerable species. Here, we document for the first time the current state of the Saudi Arabian Red Sea shark fisheries based on catch data from Jeddah fish market, one of the biggest in the Red Sea. Bi-monthly market surveys were carried out for 24 months between 2011 and 2013. Of the 30 shark species present in the Red Sea, 23 species were recorded. Notably, only four reef-associated shark species (C. amblyrhynchos, C. sorrah, C. falciformis and C. limbatus) comprised 60% of the total catch. Of all sharks landed, 75% were below the size of sexual maturity, indicating severe growth and recruitment overfishing. In combination with simultaneously conducted fisheries independent surveys (Baited Remote Underwater Video and Longline Surveys) in Saudi Arabian waters, the current data serves as an indication of the acute depletion of sharks in Saudi Red Sea waters. Given the inherent vulnerability of sharks and the overfished states of many global stocks, there is clearly an urgent need to formulate effective conservation and management plans for these rapidly declining species in a region that has so far received very little attention.
ST. CLAIR, KATHERINE; DRINNEN, ROY; METZ, TASHA; REICH, KIMBERLY; WHITTAKER, GREG; LANDRY, ANDRE. 2013.
(KS,TM,KR,GW,AL) Texas A&M University at Galveston, Galveston, TX, USA; (RD) Moody Gardens, Galveston, TX, USA
Results of a captive feeding trial to determine turnover and discrimination of 13C and 15N in epidermis of cownose rays (Rhinoptera bonasus)
Studies documenting habitat-use patterns of cownose rays (Rhinoptera bonasus) along the Texas coast are limited, with much of the available data generated by federal and state fisheries monitoring or by-catch programs. Stable isotope analyses have been increasingly used to characterize foraging ecology of various species, but only recently applied to elasmobranchs. Analysis of δ13C and δ15N retained in epidermal tissue is a possible option in discerning seasonal movements of cownose rays between inshore and nearshore habitats along the Texas coast. However, the incorporation rate and discrimination factor for epidermal tissue of cownose rays essential to this analysis have not been documented. For this reason, a subset of wild cownose rays from the Texas coast was collected for use in a controlled feeding trial to determine both isotope turnover and discrimination values. These data are key to the interpretation of carbon and nitrogen values in tissues of cownose rays captured via entanglement netting inhabiting northwestern Gulf of Mexico waters. Overall, these feeding trials will generate information that fills a void in our understanding of cownose ray ecology in this region and potentially aid in the management of marine and estuarine resources.
STEWART, JOSHUA; FERNANDO, DANIEL; BEALE, CALVIN; PILKINGTON-VINCETT, REBECCA; SEMMENS, BRICE. 2013.
(JS,BS) Scripps Institution of Oceanography, UCSD, La Jolla, CA, USA; (DF) Linnaeus University, Kalmar, Sweden; (RPV) The Manta Trust, Dorset, UK; (CB) Misool Eco Resort Conservation Center, West Papua, Indonesia
Conservation implications of oceanic manta ray spatial ecology based on stable isotope analysis and satellite tagging
Oceanic manta rays, a poorly understood, charismatic marine megafauna, are under intense fishing pressure worldwide. One of several species of Mobulid rays whose gill rakers are used as a pseudo-remedy in Traditional Chinese Medicine, thousands of mantas are killed each year in developing countries such as Sri Lanka and Indonesia. Given this intense harvest and the species’ low reproductive rates, manta populations are in decline, threatening economically important ecotourism programs in many developing countries. Despite their popularity with the public, mantas are one of the few remaining marine megafauna whose spatial ecology has not been closely examined. By investigating the movements and spatial dynamics of oceanic mantas, we intend to highlight subpopulations with increased susceptibility to overfishing, develop regional conservation recommendations, and identify critical habitats that can be protected from an ecosystem management perspective. Based on stable isotope analysis from widely disparate geographic regions, oceanic manta isotope signatures suggest distinct populations between regions. Similarly, preliminary evidence from satellite-tracked individuals indicates a high degree of regional fidelity on the order of months to years. However, tracking data also suggest individual animals exhibit different patterns of habitat use within regions. Our findings suggest that management actions should account for clear separation of populations among regions (and thus region-specific susceptibility to harvest), while spatially explicit conservation methods will be improved by understanding within-region behaviors and habitat use.
STUMP, KRISTINE; SERAFY, JOSEPH; GRUBER, SAMUEL. 2013.
(KS) University of Miami – RSMAS, Miami, FL, USA; (JS) National Oceanic and Atmospheric Administration – NMFS/SEFSC, Miami, FL, USA; (SG) Bimini Biological Field Station, Bimini, Bahamas
Effects of Habitat Loss in a Shark Nursery: Community Characterization Before and After a Disturbance
The lemon shark, Negaprion brevirostris, is a large coastal species that uses nursery habitats throughout its range. In Bimini, Bahamas, mangrove-fringed shorelines serve as nursery grounds for hundreds of juvenile N. brevirostris, providing both protection from predation and ample foraging. Recently, a significant portion of nursery habitat was destroyed during construction of a resort. Clear-cutting of mangrove forests and filling of wetlands affect not only nursery-bound neonate and juvenile N. brevirostris, but also the resources upon which they rely. To describe community diversity and structure, near-shore seining was conducted between 2009 and 2011 to quantify prey communities in both the disturbed and a nearby intact control nursery. These data were compared to data collected prior to habitat degradation, from 2000 to 2003, using identical methods, in both nurseries. Analysis-of-Similarity (ANOSIM) results showed no significant differences in abundance, biomass or occurrence of taxa in the control nursery (p>0.05), while significant differences were found for all three in the disturbed nursery (p<0.002). Species richness decreased significantly in the disturbed nursery (ANOVA, p<0.05), while no such change was seen in the control. The declines found in mean abundance of most taxa in the disturbed nursery, including those important in N. brevirostris diet, can have effects on the growth, survival, habitat use and home range of the nursery-bound sharks in this insular system.
SULIKOWSKI, JAMES; KNOTEK, RYAN; PETERSON, CASSIDY; DRIGGERS, WILLIAM; HOFFMAYER, ERIC; BUBLEY, WALTER; TSANG, PAUL. 2013.
James Sulikowski1, Ryan Knotek1, Cassidy Peterson1, William Driggers2, Eric Hoffmayer2, Walter Bubley3, Paul Tsang4
(JS,RK,CP) University of New England, Biddeford, ME, USA; (WD,EH) National Marine Fisheries Service, Pascagoula, MS, USA; (WB) Texas Parks and Wildlife Department Coastal Fisheries Division, Port O’Connor, TX, USA; (PT) University of New Hampshire, Durham, NH, USA
Observations of the Reproductive Biology of Spiny Dogfish, Squalus acanthias, along the United States East Coast; is this species more resilient than once thought?
The spiny dogfish, Squalus acanthias, is a k-selected species with a long gestation period, low fecundity, and late maturation. Increased fishing pressure from 1987 to 1996 along the U.S. east coast resulted in the stock collapsing below biomass threshold levels. Despite the implementation of a strict management plan in early 2000, the aforementioned life history characteristics of this shark suggested that the population was incapable of rebounding until 2020. However, between 2005 and 2008 a four-fold increase in the biomass of spiny dogfish was observed, an anomaly that is biologically unrealistic for this species. One possible explanation for the biomass increase may be related to the reproductive biology of this species. Although previous research has suggested a 24-month gestation period along the U.S. eastern seaboard, past studies have been geographically isolated, are antiquated, and have not analyzed the reproductive cycle over the purposed 24-month gestation period. To better understand how the reproductive biology may be contributing to the observed population increases, monthly field collections of female dogfish from distinct regions along the U.S. east coast were coupled with bimonthly ultrasound images from captive individuals in order to monitor the length and determine distinct stages of spiny dogfish gestation. Preliminary data suggests that regional variability in reproductive events (i.e. parturition), as well as an overall shorter gestation period may exist for this species along the U.S. east coast.
SZCZEPANKSI, JOHN. 2013.
University of Rhode Island, Kingston, RI, USA
Feeding ecology of the bullnose ray, Myliobatis freminvillii, in Delaware Bay
Feeding habits of many batoid elasmobranchs have been recorded, but diets, prey selection, and resource partitioning within specific populations are not fully understood. Few descriptions exist of the diet of a species throughout its entire life history. Through gut content analysis, my research examined the feeding habits of the bullnose ray, Myliobatis freminvillii, to understand the diet and trophic role of this species in the estuarine ecosystem at various life stages. I was able to collect a higher abundance of neonate and juvenile rays than expected allowing for a more comprehensive diet characterization than in past studies. 160 specimens (78 male and 82 female) were collected over two years; gastropods crustaceans, and bivalves were the most abundant prey. Pagurus longicapris was the most important prey item in all indices along with Euspira heros, Busycon sp. and Ilynassa trivitata. There were small but significant ontogenetic differences in prey weight in which consumption shifted from pagurid crustaceans to bivalves. No significant sexual or temporal differences in diet were exhibited. Significant differences in diet among collection sites indicated potential prey selection by availability. Increasing proportional abundance of smaller size classes through the summer months provides some evidence indicating that Delaware Bay may serve as a nursery area for the bullnose ray. The data shown can provide new information for future efforts in conservation, ecosystem-based fisheries management and modeling. Preliminary diet characterizations on other sympatric species and trophic ecology comparison between different batoid elasmobranch communities along the Western Atlantic Coast are also discussed briefly.
TESTERMAN, CHRISTINE B.; SHIVJI, MAHMOOD S.. 2013.
Save Our Seas Shark Center USA, Nova Southeastern University, Dania Beach, FL, USA
Comparative Patterns of Global Population Genetic Structure in Four Fisheries Exploited Sharks of Conservation Concern
The great hammerhead (Sphyrna mokarran), smooth hammerhead (S. zygaena), porbeagle (Lamna nasus), and bull shark (Carcharhinus leucas) are all commercially exploited. The hammerheads and porbeagles recently received heightened conservation status via recommended CITES Appendix II listings. We evaluated the genetic population structure of these species using globally distributed sample sets (S. mokarran n=312, S. zygaena n=332, L. nasus n=224 and C. leucas n=490) and nuclear markers and/or mitochondrial control region (mtCR) sequences. All four species showed statistically significant genetic partitioning on large scales, i.e., between hemispheres (L. nasus mtCR fST = 0.8273) or oceanic basins (S. mokarran mtCR fST = 0.8745, nuclear FST = 0.1113; S. zygaena mtCR fST = 0.8159, nuclear FST = 0.0495; C. leucas nuclear FST = 0.1564). Furthermore, S. zygaena mtCR sequences indicated statistically significant matrilineal genetic structuring within oceanic basins, but no intra-basin structure was detected with microsatellites. S. mokarran showed shallow but statistically significant genetic structure within oceanic basins with both nuclear and mitochondrial data, albeit with some differences between the two marker types in fine scale patterns involving northern Indian Ocean samples. A microsatellite assessment of C. leucas demonstrated no population structuring within the Atlantic or Indo-Pacific, with the exception that samples from Fiji were differentiated from the remaining Indo-Pacific Ocean locations.
In contrast, the L. nasus mtCR and nuclear ITS2 sequences revealed strong northern vs. southern hemispheric population differentiation, but no differentiation within these hemispheres. These geographic patterns of genetic structure will inform stock delineation and other conservation and management efforts.
TRIBUZIO, CINDY; BLOOD, CALVIN; MATTA, BETH; GBURSKI, CHRIS; BUBLEY, WALLY; KRUSE, GORDON. 2013.
(CT) Auke Bay Laboratories, Juneau, AK, USA; (CB,BM,CG) Alaska Fisheries Science Center, Seattle, WA, USA; (WB) Texas Parks and Wildlife, Lavaca, TX, USA; (GK) University of Alaska Fairbanks, Fairbanks, AK, USA
The Spiny Issue of Ageing Spiny Dogfish: Historical Dogma vs. New Methods
The dogma of using the dorsal fin spine to age spiny dogfish (Squalus suckleyi) has been in existence for over 30 years. With these well established methods, the species has a rather long history of published literature on age and growth. However, a problem with this method is that the dorsal fin spine, which protrudes from the body into the environment, is sometimes broken and often worn, thus creating lost or difficult-to-read annuli. Recent research on an Atlantic congener (Squalus acanthias) found that a technique using histological staining of vertebrae thin sections made it possible to count annuli, thus eliminating the sources of uncertainty associated with worn spines. However, this vertebral method has yet to be tested in the much longer lived North Pacific spiny dogfish. Our study examines both age structures and compares inter- and intra-reader as well as inter-lab variability in reading annuli to determine which method produces the most precise ages for the North Pacific spiny dogfish. Results suggest a substantial decrease in intra- and inter-reader variability when the vertebrae method is compared to the dorsal fin spine method. Preliminary analyses also show that there are multiple sources of measurement error when using the spine method, sources that do not exist with the vertebrae method, and that inter-reader variance increases substantially more with increasing age with the spine method than with the vertebrae method.
VAUDO, JEREMY; WETHERBEE, BRADLEY; WOOD, ANTHONY; HOWEY-JORDAN, LUCY; SHIVJI, MAHMOOD. 2013.
(JV,LHJ,MS) Guy Harvey Research Institute, Oceanographic Center, Nova Southeastern University, Dania Beach, FL, USA; (BW) University of Rhode Island, Kingstown, RI, USA; (AW) NOAA, NMFS, NEFSC, Woods Hole, MA, USA
Movements of mako sharks (Isurus oxyrinchus) tagged in the western North Atlantic Ocean
The mako shark (Isurus oxyrinchus) is a wide ranging species found in temperate and tropical waters worldwide. Although mako sharks are regularly encountered on the east coast of the United States, knowledge of their movements in this region is primarily based on catch records and tag returns. To investigate the movements of mako sharks tagged in the western North Atlantic Ocean, six individuals (130 – 244 cm FL) were tagged with pop-up satellite archival tags off the coast of Rhode Island during summers between 2004 and 2008. All six tags reported, providing depth and temperature data from a span of 412 days (range: 12 – 183 days). The two sharks tracked for over 100 days traveled south during autumn with one shark reaching South Carolina (displacement: ~1100 km over 183 days) and the other reaching the Bahamas (displacement: ~2000 km over 122 days). Mako shark vertical habitat use appears to be constrained by the thermocline. Sharks typically remained in the mixed layer, but spent more time below the thermocline during the daytime, with two sharks diving deeper than 500 m (maximum depth: 866 m). Mako sharks encountered a wide range of temperatures. The minimum and maximum temperatures experienced were 5.2 and 27.1°C, respectively. Sharks also tended to make deeper dives in warmer water masses, although minimum temperatures experienced were similar regardless of water mass, suggesting temperature may limit dive depths.
VAUDO, JEREMY; WETHERBEE, BRADLEY; WOOD, ANTHONY; HOWEY-JORDAN, LUCY; SHIVJI, MAHMOOD. 2013.
Jeremy Vaudo1, Bradley Wetherbee2, Anthony Wood3, Lucy Howey-Jordan1, Mahmood Shivji1
(JV,LHJ,MS) Guy Harvey Research Institute, Oceanographic Center, Nova Southeastern University, Dania Beach, FL, USA; (BW) University of Rhode Island, Kingstown, RI, USA; (AW) NOAA, NMFS, NEFSC, Woods Hole, MA, USA
Movements of mako sharks (Isurus oxyrinchus) tagged in the western North Atlantic Ocean
The mako shark (Isurus oxyrinchus) is a wide ranging species found in temperate and tropical waters worldwide. Although mako sharks are regularly encountered on the east coast of the United States, knowledge of their movements in this region is primarily based on catch records and tag returns. To investigate the movements of mako sharks tagged in the western North Atlantic Ocean, six individuals (130 – 244 cm FL) were tagged with pop-up satellite archival tags off the coast of Rhode Island during summers between 2004 and 2008. All six tags reported, providing depth and temperature data from a span of 412 days (range: 12 – 183 days). The two sharks tracked for over 100 days traveled south during autumn with one shark reaching South Carolina (displacement: ~1100 km over 183 days) and the other reaching the Bahamas (displacement: ~2000 km over 122 days). Mako shark vertical habitat use appears to be constrained by the thermocline. Sharks typically remained in the mixed layer, but spent more time below the thermocline during the daytime, with two sharks diving deeper than 500 m (maximum depth: 866 m). Mako sharks encountered a wide range of temperatures. The minimum and maximum temperatures experienced were 5.2 and 27.1°C, respectively. Sharks also tended to make deeper dives in warmer water masses, although minimum temperatures experienced were similar regardless of water mass, suggesting temperature may limit dive depths.
VAUDO, JEREMY; WETHERBEE, BRADLY; WOOD, ANTHONY; HOWEY-JORDAN, LUCY; SHIVJI, MAHMOOD. 2013.
(JV,LHJ,MS) Guy Harvey Research Institute, Oceanographic Center, Nova Southeastern University, Dania Beach, FL, USA; (BW) University of Rhode Island, Kingstown, RI, USA; (AW) NOAA, NMFS, NEFSC, Woods Hole, MA, USA
Movements of mako sharks (Isurus oxyrinchus) tagged in the western North Atlantic Ocean
The mako shark (Isurus oxyrinchus) is a wide ranging species found in temperate and tropical waters worldwide. Although mako sharks are regularly encountered on the east coast of the United States, knowledge of their movements in this region is primarily based on catch records and tag returns. To investigate the movements of mako sharks tagged in the western North Atlantic Ocean, six individuals (130 – 244 cm FL) were tagged with pop-up satellite archival tags off the coast of Rhode Island during summers between 2004 and 2008. All six tags reported, providing depth and temperature data from a span of 412 days (range: 12 – 183 days). The two sharks tracked for over 100 days traveled south during autumn with one shark reaching South Carolina (displacement: ~1100 km over 183 days) and the other reaching the Bahamas (displacement: ~2000 km over 122 days). Mako shark vertical habitat use appears to be constrained by the thermocline. Sharks typically remained in the mixed layer, but spent more time below the thermocline during the daytime, with two sharks diving deeper than 500 m (maximum depth: 866 m). Mako sharks encountered a wide range of temperatures. The minimum and maximum temperatures experienced were 5.2 and 27.1°C, respectively. Sharks also tended to make deeper dives in warmer water masses, although minimum temperatures experienced were similar regardless of water mass, suggesting temperature may limit dive depths.
WENG, KEVIN; HONEYBRINK, RANDY. 2013.
(KW) University of Hawaii, Honolulu, HI, USA; (RH) Division of Aquatic Resources, Honolulu, HI, USA
Occurrence of White Sharks (Carcharodon carcharias) in Hawaiian Waters
White sharks were observed and captured in Hawaii prior to Western contact (1778), and their presence continues to be documented on rare and brief occasions. Sightings of white sharks often result in considerable media attention, and there is a great deal of public interest in their occurrence. Some purported sightings may have been misidentifications of mako sharks, as was demonstrated in a recent case. Our goal was to provide an updated, definitive record of white shark presence in Hawaii, which can be used as a reference for continued studies, and for media and public informational purposes. We compiled sighting and attack records, catch data from shark control programs, observations from submersibles and remote cameras, and published satellite tag records in an attempt to understand the origins of Hawaii’s white sharks, and seasonality of their occurrences. We evaluated life history hypotheses with regard to seasonal differences in the presence of male and female white sharks. We also proposed a new metric for distinguishing white sharks from other related species. In an attempt to provide a clearer picture of our current understanding about the presence of white sharks in Hawaii, it is our intention to make the information from this study available to the media and public in a user-friendly version through various outreach efforts.
WHITNEY, NICHOLAS; WHITE, CONNOR; ANDERSON, PAUL; GLEISS, ADRIAN; SKOMAL, GREGORY; HUETER, ROBERT. 2013.
(NW,CW,RH) Mote Marine Laboratory, Sarasota, FL, USA; (PA) Mystic Aquarium, a division of Sea Research Foundation, Inc., Mystic, CT, USA; (AG) Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA; (GS) Massachusetts Division of Marine Fisheries, New Bedford, MA, USA
Hook, line, and sinker? Using accelerometers to assess post-release behavior in sharks.
Although post-release mortality in elasmobranchs can be measured by a variety of acoustic and satellite telemetry techniques, many of these are cost- or labor-intensive and sometimes fail to give definitive answers on shark mortality. Studies that have quantified a recovery period in pelagic sharks have used changes in diving patterns that may not be applicable to coastal species that are restricted by bottom depth. We applied acceleration data loggers (ADL’s) to measure fine-scale swimming behavior of blacktip sharks (Carcharhinus limbatus, N=20) caught in the Florida recreational shark fishery. Mortalities (N=3) all took place within 2 h after release and were apparent from static depth data and the cessation of tailbeat activity, whereas surviving sharks were monitored for 7 to 55 h (27 + 18 h, mean + SD). Using the data collected from ADLs, we evaluated 58 metrics of fine-scale swimming behavior for their potential to indicate a recovery period. We used nonlinear mixed modeling to fit a four-parameter logistic function to these metrics. Once analyzed, 18 of these metrics displayed a significant logistic relationship with time after release, with mean recovery periods from each metric ranging from 7.2 to 14.4 h after release (9.9 + 1.9 h, mean + SD). Our results show the utility of accelerometers to provide definitive information on animal outcomes and the broad applicability of these data to the study of post-release mortality and recovery in coastal sharks.
WYFELS, JENNIFER. 2013.
University of Delaware, Newark, DE, USA
The Skate Genome Project
The North East Bioinformatics Collaborative (NEBC) of the North East Cyberinfrastructure Consortium (NECC) is a team of bioinformatics experts from Vermont, New Hampshire, Rhode Island, Maine and Delaware responsible for sequencing the genome of the little skate, Leucoraja erinacea. Chondrichthyan fishes are important model organisms for comparative genomics because of their basal position in vertebrate evolutionary history and fundamental gnathostome characteristics. The genome of a Stage 32 embryo was sequenced using whole genome shotgun sequencing and Illumina high-throughput, next generation sequencing at 59x coverage. An initial de novo genome assembly represents approximately 40% of the estimated 3.4 Gbp genome. Genome project sequence data are registered under GenBank BioProject PRJNA60893 and the raw data is available using NCBI’s Sequence Read Archive (SRA026856). Acting as a nexus for curation activities and dissemination of project data, a web portal, SkateBase (http://skatebase.org) has been developed. Project data including GBrowse views for mitochondrial genomes of 3 elasmobranch species, SkateBLAST (a tool for homology searching), and training materials from three annotation workshops are accessible through SkateBase. Provisionary genome annotations are given for proteins with evidence of homology through sequence similarity searches. Other large scale sequencing projects deposited in NCBI databases are linked, making Skatebase a comprehensive genomic resource for the chondrichthyan research community. Through outreach, we expect to add features and tools of interest as suggested by the research community. Efforts are ongoing to enhance and streamline the genome annotation workflow, as we look toward larger-scale functional and structural community annotation of the L. erinacea genome.
YAGAMUCHI, ATSUKO; FURUMITSU, KEISUKE. 2013.
Nagasaki University, Nagasaki, Japan
Long-term biological study of longheaded eagle ray Aetobatus flagellum in Ariake Bay Japan
The number of longheaded eagle ray, Aetobatus flagellum, in south-western coastal areas of Japan has increased since the late 90s. A. flagellum feeds on bivalves and is considered to be responsible for the decrease of the bivalve catches in coastal areas such as Ariake Bay. In an attempt to reduce the predation pressure on bivalves, a predator control program was implemented in 2001. Since the biology of A. flagellum was poorly known at that time, we started examining their life history, behavior, seasonal migrations, and population structure of the ray populations since 2001. Our findings showed that A. flagellum is a seasonal resident of Ariake Bay, with numbers peaking in summer. Their low fecundity and slow rate of sexual maturation suggested that the predator control programs have been effective in reducing eagle ray population size. We hypothesize that the drastic changes in Ariake Bay ecosystem, such as the marked increase observed in eagle ray numbers, may have occurred in response to a decrease of the number of apex predators such as sharks. We therefore clarified the fish fauna of the bay and are currently investigating food web structure and ecosystem functioning in the bay. Here, we will present our recent findings on the biology of A. flagellum, with a focus on behavior and seasonal migration patterns inferred using Argos satellite transmitters, pop-up satellite archival tags, and acoustic coded transmitters. We will also discuss the need for a new ecosystem monitoring method to replace the current predator control programs.
YOPAK, KARA; WASSELL, REBECCA; GOH, GRACE; HEEL, KATHY; NORTHCUTT, R. GLENN; COLLIN, SHAUN. 2013.
(KY,RW,GG,SC) School of Animal Biology and the UWA Oceans Institute, University of Western Australia, Crawley, WA, Australia; (KH) School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, WA, Australia; (RGN) Department of Neurosciences and Scripps Institution of Oceanography, University of California San Diego, San Diego, CA, USA
Are Sharks “Smart”? Developing Quantitative Measures of Cognitive Ability in Fishes
Relationships between the body, brain, and major brain regions have traditionally been used to infer cognitive abilities across a range of vertebrates, providing vital information about life history traits, behavior and “intelligence”. Indeed, broad variability has been documented in the size and complexity of these brain areas in chondrichthyans (sharks, batoids, and chimaeras), which has been associated with differences in habitat and/or specific behavior patterns. However, new neuronal scaling rules based on a method of accurately assessing the number of neurons in the brain in mammals, isotropic fractionation [see Herculano-Houzel and Lent, 2005, J Neurosc], suggest that brain mass may be a poor predictor of cognitive ability and enhanced associative function. Here, we present the first application of this technique in fishes, using the Port Jackson shark, Heterodontus portusjacksoni, to accurately assess total neuron number (as compared to non-neuronal glia) in the brain and its component parts. We present detailed strategies for the optimisation of brain homogenisation, neuronal staining, calibration, imaging, and quantification of brain cells in fishes. Based on preliminary results, we suggest the isotropic fractionation method may serve as an effective tool to assess functional ability and processing power in the brains of chondrichthyans. These data will pave the way for future work to assess whether the number of neurons within the major brain regions show a linear relationship or reveals differential rates of addition in relation to higher cognitive abilities and/or more complex behavioral repertoires in chondrichthyans, with implications for how “intelligence” has evolved across vertebrates.