Carcharias Taurus Research Articles

Effective population size of the critically endangered east Australian grey nurse shark Carcharias taurus

Effective population size of the critically endangered east Australian grey nurse shark Carcharias taurus

Reproductive philopatry in a coastal shark drives age-related population structure

The cosmopolitan lamniform shark Carcharias taurus (commonly known as the ragged-tooth, grey nurse or sand tiger shark) is threatened by overexploitation in parts of its range. Return migrations of females to specific nursery areas suggest that females exhibit reproductive philopatry, a behaviour that over time might lead to genetically isolated subpopulations over various spatial scales. To investigate genetic evidence for reproductive philopatry, genetic data from mitochondrial and microsatellite markers were generated for 104 young-of-the-year and juvenile sharks. Comparing the smallest versus the largest young sharks revealed a pattern of size-related differentiation between nurseries that was only found in the smaller size class. This not only confirms reproductive philopatry of their mothers, but is also in line with previous observations of larger juvenile sharks increasing their migration range and moving between sites. Our results highlight the need to target young-of-the-year sharks when investigating reproductive philopatry to exclude roaming individuals that obscure size-related signals of genetic differentiation. Given the species’ high susceptibility to overexploitation, the evidence for reproductive philopatry is of direct importance to the management and conservation of C. taurus worldwide. As many nursery areas as possible should be protected to ensure that the number of locally resident juveniles and the pool of the returning females remain stable in the long term. This may warrant protected areas, or time-area closures, prohibiting exploitation in the nursery areas during pupping season.

Effects of pre-treatments on bulk stable isotope ratios in fish samples: A cautionary note for studies comparisons.

Stable isotope analysis (SIA) has revolutionised ecological studies over the past thirty years. One of the major fields where SIA is applied in the marine environment is related to the definition of ecosystem structure and function. With marine top predators such as sharks, SIA is a method of choice because tissue samples can be collected without the sacrifice of the animal. In elasmobranch research, the influence of compounds such as urea, trimethylamine oxide and lipids must be considered when using stable isotopes as ecological markers. Currently, a range of pre-treatments are used to chemically remove these molecules prior to SIA. This study investigated the impact of eleven commonly used pre-treatments on carbon and nitrogen contents and C:N atomic ratio, as well as carbon and nitrogen SI ratios in elasmobranch tissues and its prey, measured by isotope ratio mass spectrometry. Three tissues were tested: blood and muscle of the ragged-tooth shark Carcharias taurus, and muscle of one teleost species, the Cape knifejaw Oplegnathus conwayi. Compared with untreated samples, no trend or generalisation could be highlighted with the influence of pre-treatments being species-, tissue- and chemical-element-dependent. For the δ13 C and δ15 N values, differences among pre-treatments were as high as 3‰, therefore potentially leading to erroneous ecological interpretation. The chemical properties of compounds (e.g. urea, lipids) combined with the polarity of solutions (e.g. water, solvents) explained a large part of these observations. This study highlights that pre-treatments need to be considered especially when comparing carbon and nitrogen stable isotope ratios between studies. The results of this study provide a call to all stable isotope researchers to make a concerted effort to standardise pre-treatment methods. This is crucial as global reviews are becoming increasingly more informative.

Genomic resources for the spotted ragged-tooth shark Carcharias taurus

Genomic data can be a useful tool in the management and conservation of biodiversity. Here, we report the development of genomic resources for the spotted ragged-tooth shark Carcharias taurus using genome-wide DNA data from Illumina next-generation sequencing. We explored two commonly used genetic marker types: microsatellites and mitochondrial DNA. A total of 4 394 putative microsatellites were identified, of which 10 were tested on 24 individuals and found to have ideal properties for population genetic analyses. Additionally, we reconstructed the first complete mitochondrial genome of a South African spotted ragged-tooth shark, and highlight the most informative gene regions to facilitate future primer design. The data reported here may serve as a resource for future studies and can ultimately be applied in the sustainable conservation and fisheries management of this apex predator.

Catching of a Large Specimen of Smalltooth Sand Tiger Odontaspis ferox (Odontaspididae) near the Southern Part of Walvis Ridge (Southeastern Atlantic)

Catching of extremely large (520 cm) specimens of smalltooth sand tiger Odontaspis cf. ferox (Odontaspididae) near the southern part of Walvis Ridge (Southeastern Atlantic open waters) is documented for the first time. This species was found earlier in the Atlantic Ocean in the near-continental waters and island regions of the northeastern Atlantic from the Bay of Biscay to Morocco, including the Mediterranean Sea. In the open waters of the southeastern Atlantic, the species was not recorded previously.

An assessment of juvenile sand tiger (Carcharias taurus) activity patterns in a seasonal nursery using accelerometer transmitters

Telemetry transmitters incorporating accelerometers have recently emerged as powerful tools for investigating the activity patterns of individuals and groups of individuals in nearshore environments. Data obtained from these devices provide not only a time series of animal occurrence at acoustic receivers, but also a direct measure of animal activity, which can be used to quantify trends in activity states over time and in relation to exogenous factors. Here we used passive acoustic accelerometry to examine trends in the activity and swimming depth of eight juvenile sand tigers (Carcharias taurus) in Plymouth, Kingston, Duxbury (PKD) Bay, Massachusetts, USA, a recently identified nursery area. We applied a novel geostatistical modeling approach that accounts for both latent spatial and individual variation to assess the effects of time of day, tidal stage, water temperature, and lunar phase on activity patterns at both a population- and individual-level. The best-fitting model indicated that juvenile sand tigers were more active and more likely to be detected at the surface at night and during the new moon; water temperature was also a predictor of surface activity. Collectively, our results confirm conventional wisdom that sand tigers are slow-moving fish that are more active at night and provide evidence that high activity in PKD Bay may be indicative of foraging activity.

A new report on the clasper movements of a captive Sand Tiger Shark Carcharias taurus (Lamniformes: Odontaspididae) and a possible reason for the behaviour

Elasmobranchs present four clasper movements, which can be seen in different contexts from mating to no obvious reason. Three movements have been reported in Carcharias taurus and here the first occurrence of clasper flaring in this species is described. Clasper flaring was observed while other species were in a reproductive state and their aggressive behaviour towards the subject of this study was also observed.

New records of sharks (Elasmobranchii) from the Andaman and Nicobar Archipelago in India with notes on current checklists.

The diversity of sharks occurring off the Andaman and Nicobar Archipelago in India has received increased attention in recent years. Yet, available checklists are out of date, often with inaccurate information and a number of commercially important species have not been documented through research and fish landing surveys. Here we report on shark species examined during fish landing surveys conducted from January 2017 to April 2018. Records of twelve previously unreported species from the archipelago are presented and include the bignose shark (Carcharhinus altimus), pigeye shark (Carcharhinus amboinensis), bull shark (Carcharhinus leucas), snaggletooth shark (Hemipristis elongata), slender weasel shark (Paragaleus randalli), Arabian smoothhound shark (Mustelus mosis), Indonesian houndshark (Hemitriakis indroyonoi), sand tiger shark (Carcharias taurus), Indonesian bambooshark (Chiloscyllium hasseltii), tawny nurse shark (Nebrius ferrugineus), dwarf gulper shark (Centrophorus atromarginatus), and the Indonesian shortsnout spurdog (Squalus hemipinnis). These records increase the reported shark species for the archipelago from 47 to 59 and for India from 114 to 116. Additionally, a size extension in the total length of C. hasseltii by 27 cm and of P. randalli by 8 cm is reported. Owing to the bio-geographical location of these islands, species diversity around the archipelago is unique and appears to overlap with that of southeast Asia. With increasing reports of over-exploitation and the operation of a targeted shark fishery by distant water fleets in these waters, the limited information on shark diversity from this region is of concern. Systematic and long-term monitoring of catches, combined with accurate species identification, is crucial to provide information on management measures.

On the complexity of shark bite wounds: From associated bacteria to trauma management and wound repair.

Therapeutic study, level V.

Mitochondrial DNA haplotype diversity and origin of captive sand tiger sharks (Carcharias taurus)

The sand tiger shark (Carcharias taurus) is listed as globally vulnerable with geographically confined and disrupted global populations with little or no gene flow between them. Captive breeding in aquaria of these sharks would reduce the need to populate displays with wild-caught individuals, however, sand tigers are notoriously difficult to breed in captivity. In this study we analysed 520bp of the mitochondrial D-loop to assess the haplotype diversity of 19 captive sand tiger sharks, from UK and US aquaria sampled in a non-invasive fashion through DNA extracted from shed teeth. Data obtained were compared to known geographically mapped wild haplotypes to establish whether individuals from different global populations are being housed together. We were able to identify the haplotype of a minimum of ten of the 19 sharks, detecting four different haplotypes, with a previously undescribed haplotype (Haplotype K) found from a captive sample. A major genetic subdivision between the haplotypes of the North West Atlantic and the other global populations has been previously shown from population genetic analyses. Our results indicate that captive sharks can be from either side of this subdivision and occasionally these can be co-housed in the same aquarium. Since sharks with highly divergent genetic ancestry are being kept together, these findings have implications for conservation efforts regarding the individual needs of sand tiger shark populations and for captive breeding program success rates.

Spatial ecology of Carcharias taurus in the northwestern Mid-Atlantic coastal ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 597:191-206 (2018) - DOI: https://doi.org/10.3354/meps12592 Spatial ecology of Carcharias taurus in the northwestern Mid-Atlantic coastal ocean D. E. Haulsee1,*, M. W. Breece1, L. M. Brown2, B. M. Wetherbee3, D. A. Fox2, M. J. Oliver1 1College of Earth, Ocean and the Environment, University of Delaware, Lewes, DE 19958, USA 2Department of Agriculture and Natural Resources, Delaware State University, Dover, DE 19901, USA 3Department of Biological Sciences, University of Rhode Island, Kingston, RI 02811, USA *Corresponding author: dhaulsee@udel.edu ABSTRACT: The sand tiger shark Carcharias taurus is a highly migratory coastal species with declining populations worldwide. This species exhibits many behaviors that make coastal sharks difficult to manage, including aggregatory behavior, sexual segregation, and large-scale migrations through shallow coastal waters with many opportunities for human interactions. Sand tigers from the Western North Atlantic subpopulation are known to seasonally inhabit Delaware Bay and surrounding coastal waters. This region has been recommended as a habitat area of particular concern for the Western North Atlantic sand tiger population, and increased understanding of their movements and habitat requirements will facilitate management efforts. We developed models to predict sand tiger occupancy using spatially dynamic environmental predictors. Our models predicted sand tiger (juveniles, adult males, adult females, and all sharks combined) occurrences in 2 study regions, the Delaware Bay and the western Mid-Atlantic coastal ocean. Sea surface temperature, day of year, water depth, and remote sensing reflectance at 555 nm were the most important environmental predictors of occurrence, and correctly predicted 80-89% of sand tiger acoustic telemetry records in the 2 study regions. Our models predicted differences in the timing and location of occurrences among juveniles and adults, as well as areas where these life history stages overlap in the Mid-Atlantic coastal ocean. Our hope is that a daily forecast of sand tiger occurrence from our modeling efforts could be useful for conservation and management efforts in this important region, as well as for studying the spatial and behavioral ecology of this important top predator. KEY WORDS: Acoustic telemetry · Generalized additive mixed model · Predictive habitat modeling · Species distribution · Sand tiger shark · Carcharias taurus Full text in pdf format Supplementary material PreviousNextCite this article as: Haulsee DE, Breece MW, Brown LM, Wetherbee BM, Fox DA, Oliver MJ (2018) Spatial ecology of Carcharias taurus in the northwestern Mid-Atlantic coastal ocean. Mar Ecol Prog Ser 597:191-206. https://doi.org/10.3354/meps12592 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 597. Online publication date: June 11, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Fish and habitats on wellhead infrastructure on the north west shelf of Western Australia

When production ceases, offshore oil and gas wells are taken out of service which involves safely plugging, abandoning and usually removing most of the associated subsea equipment. This process must consider impacts to marine ecosystems to meet regulatory requirement and for best environmental practice. However, there is a paucity of information globally on the ecosystem value of these structures, despite the many thousands that are installed throughout our oceans. This study provides the first assessment of fish assemblages and habitats formed by colonising invertebrates on oil and gas wellheads and associated infrastructure in depths of 78–825 m on the north west shelf of Western Australia. Video footage was obtained from Remotely Operated Vehicles deployed by industry on 25 wellhead structures, with six surveyed in each of four distinct depth zones: 78–85 m, 125–135 m, 350–395 m and 490–550 m, and one in 825 m depth. A total of 7278 individual fish from 60 species and 35 families were observed. Commercially important lutjanid (snapper) and epinephelid (grouper) species were common and most abundant on well infrastructure to depths of 135 m, but were absent in depths > 350 m. An as yet unidentified species of roughy, recorded here as Gephyroberyx sp. was the most common fish species observed on well infrastructure in depths > 350 m. Two speckled swellsharks (Cephaloscyllium speccum), believed to be endemic to north-west Australia, were observed for the first time in situ. Numerous fish species were observed at depths beyond their known limits and two IUCN vulnerable species were recorded: the grey nurse shark (Carcharias taurus; 135 m depth) and the round ribbontail ray (Taeniura meyeni; 78 m depth). Fish assemblages and colonising invertebrate habitats present on wellheads and associated infrastructure were strongly influenced by depth, age and height of the structures. Older, taller wellheads in depths < 135 m possessed greater abundances of groupers, snappers, site-attached reef species, and transient pelagic fish species. Beyond 350 m depth, the number of species and total fish abundance declined markedly, as did the percent cover of ascidians, black/octocorals, sponges and Gorgonocephalidae (basket stars) observed growing on the infrastructure. Deeper structures were characterised by an abundance of Gephyroberyx sp. and, while these structures had less colonising invertebrate coverage in general, crinoids (490–550 m) and crustacea (barnacles; 350–395 m) were dominant at these depths. With very little known about marine ecosystems in depths > 100 m, or about wellheads as a type of subsea structure, this study demonstrates the ecological value of ROV footage obtained during industry operations and is indicative of the importance of subsea oil and gas infrastructure as a habitat for fish, and potentially as structures with value to fisheries.

Occurrence of the vulnerable smalltooth sand tiger shark, Odontaspis ferox , in the Canary Islands, first evidence of philopatry

Occurrence of the vulnerable smalltooth sand tiger shark, <i>Odontaspis ferox</i> , in the Canary Islands, first evidence of philopatry

Development of the Lunate-Shaped Caudal Fin in White Shark Embryos.

The lunate-shaped caudal fin in lamnid sharks is a morphological specialization for their thunniform mode of locomotion, but its developmental process during gestation has been poorly investigated. Observations of 21 embryonic specimens of the white shark (Carcharodon carcharias) revealed that their caudal fin morphology drastically changes from strongly heterocercal to lunate-shaped through ontogeny. This morphological change involves (1) rapid elongation of the ventral lobe, (2) increased upward curvature of the vertebra within the caudal fin, and (3) formation of keels at both lateral sides of the caudal fin base. These morphological changes are probably shared among the members of the family Lamnidae and are in contrast with the developmental process of the heterocercal tail in the lamniform Carcharias taurus, in which the caudal fin morphology is almost unchanged through the late gestation period. Anat Rec, 301:1068-1073, 2018. © 2018 Wiley Periodicals, Inc.

The occurrence of early Pleistocene marine fish remains from the Gulf Coast of Mobile County, Alabama, USA

We examined 91 specimens recovered as beach wash on the shores of Dauphin Island and the nearby Sand/ Pelican Island Complex located in the northern Gulf of Mexico in Mobile County, Alabama, USA. A total of 12 unequivocal taxa were identified within our sample, including Carcharias taurus, Carcharodon carcharias, Cosmopolitodus hastalis, Carcharhinus leucas, Carcharhinus sp. cf. C. longimanus, Carcharhinus obscurus, Carcharhinus sp. cf. C. plumbeus, Negaprion brevirostris, Galeocerdo cuvier, Hemipristis serra, Aetobatus sp., and Diodontidae. Although not collected in situ, the preservation of the teeth, the biostratigraphic ranges of the taxa, and local stratigraphy suggests these fossils were derived from the shallow lower Pleistocene, Biloxi Formation and may be as young as Calabrian in age. Two extinct taxa in our sample, C. hastalis and H. serra, are among the stratigraphically youngest occurrences for each species. A comparison to extant representatives suggests this fossil assemblage preferred a warm, shallow, near-shore habitat with a water depth of 100 m or less. These fossils represent the first Quaternary marine vertebrates reported from Alabama.

Sustainability of threatened species displayed in public aquaria, with a case study of Australian sharks and rays

Zoos and public aquaria exhibit numerous threatened species globally, and in the modern context of these institutions as conservation hubs, it is crucial that displays are ecologically sustainable. Elasmobranchs (sharks and rays) are of particular conservation concern and a higher proportion of threatened species are exhibited than any other assessed vertebrate group. Many of these lack sustainable captive populations, so comprehensive assessments of sustainability may be needed to support the management of future harvests and safeguard wild populations. We propose an approach to identify species that require an assessment of sustainability. Species at risk of extinction in the wild were considered to be those assessed as threatened (CR, EN or VU) on the IUCN Red List of Threatened Species, or data deficient species that may be at an elevated risk of extinction due to life history traits and habitat associations. We defined sustainable captive populations as self-maintaining, or from a source population that can sustain harvest levels without risk of population declines below sustainable levels. The captive breeding and wild harvest records of at risk species displayed by Australian aquaria were examined as a case study. Two species, largetooth sawfish Pristis pristis and grey nurse shark Carcharias taurus, were found to have unsustainable captive populations and were identified as high priorities for comprehensive sustainability assessments. This review highlights the need for changes in permitting practices and zoo and aquarium record management systems to improve conservation outcomes for captive elasmobranchs.

Cold fins, murky waters and the moon: what affects shark catches in the bather-protection program of KwaZulu–Natal, South Africa?

The influence of environmental variables on shark catch in the bather-protection program along the eastern coast of South African was investigated for 11 commonly caught species (Carcharhinus limbatus, C. obscurus, C. brachyurus, C. plumbeus, C. brevipinna, C. leucas, Carcharodon carcharias, Carcharias taurus, Sphyrna lewini, S. zygaena, Galeocerdo cuvier). Data for the period 1986–1994 were analysed using generalised additive models and generalised additive mixed models. The influence of temporal and spatial factors was respectively considered and removed within a standardisation procedure to investigate and predict the influence of lunar cycle, sea-surface temperature (SST) and water visibility on daily catch. The catches of C. taurus and C. brevipinna were significantly affected by all three factors. Catches of all other species were affected by at least one of the three factors, e.g. six were affected by lunar phase, six by SST and seven by water visibility. The results suggested that measurable, predictable relationships exist between environmental conditions and presence and, consequently, catch of shark species in this program. Understanding these relationships could be useful to mitigate against unwanted catch and to further reduce risk for bathers.

Dentition facilitates the release of encapsulated Ragged-tooth Shark (Carcharias taurus) embryos

The capture of four female Ragged-tooth Sharks, Carcharias taurus, in the early stages of pregnancy in the bather protective nets along the KwaZulu-Natal coastline provided an opportunity to investigate embryonic development. A total of 31 embryos, 8–225 mm total length, were found. Of these, 15 were encapsulated and 16 were found free-floating in the uterus. Six embryos, three of which were encapsulated (35–50 mm) and three free-floating (36–52 mm), were examined under both light and scanning electron microscopy. The embryos possessed tooth-like structures. Spectral analysis of these structures revealed the presence of calcium, phosphorus, fluoride and oxygen, which supports the hypothesis that they are teeth. These teeth would enable embryos to escape encapsulation. These free-floating embryos are the smallest on record, with the previous smallest being a 40 mm embryo. These findings would now amend the current literature of C. taurus embryology. These results could affect the current understanding of C. taurus reproduction and biology and may impact any current breeding programs that are attempting to increase the fecundity of these species.

New records from Banks Island expand the diversity of Eocene fishes from Canada’s western Arctic Greenhouse

Eocene vertebrates from the Canadian Arctic, including sharks, bony fishes, turtles, crocodylians, birds, and mammals, have provided strong evidence for relatively warm ice-free conditions in the Arctic during the Eocene Greenhouse interval. Recent expeditions to Banks Island (Northwest Territories) in the western Arctic have recovered a relatively more marine-influenced Eocene fauna, including sand tiger sharks, bony fishes, turtle shell fragments, and a single crocodylian specimen. We report here on new additions to this fauna, including diagnostic large scales that confirm the presence of Amia in the western Arctic. One very large lateral line scale corresponds to a fish approximately 1.4 m in total length, larger than the maximum size for extant Amia calva. We also recovered approximately 100 distinctive teeth that we assign to the teleost genus Eutrichiurides, which is otherwise known from lower latitude Paleogene sites in the United States, India, Africa, and Europe. The genus is interpreted as an a...

Eocene sand tiger sharks (Lamniformes, Odontaspididae) from the Bolca Konservat-Lagerstätte, Italy: palaeobiology, palaeobiogeography and evolutionary significance

Here we report the first record of one of the most common and widespread Palaeogene selachians, the sand tiger shark Brachycarcharias, from the Ypresian Bolca Konservat-Lagerstätte. The combination of dental character of the 15 isolated teeth collected from the Pesciara and Monte Postale sites (e.g. anterior teeth up to 25 mm with fairly low triangular cusp decreasing regularly in width; one to two pairs of well-developed lateral cusplets; root with broadly separated lobes; upper teeth with a cusp bent distally) supports their assignment to the odontaspidid Brachycarcharias lerichei (Casier, 1946), a species widely spread across the North Hemisphere during the early Palaeogene. The unambiguous first report of this lamniform shark in the Eocene Bolca Konservat-Lagerstätte improves our knowledge concerning the diversity and palaeobiology of the cartilaginous fishes of this palaeontological site, and provides new insights about the biotic turnovers that involved the high trophic levels of the marine settings after the end-Cretaceous extinction.