Nurse Shark Ginglymostoma Cirratum Research Articles

Observations of hypomelanosis in the nurse shark Ginglymostoma cirratum.

Hypomelanosis refers to a suite of skin pigment abnormalities, including albinism, leucism and piebaldism. While documented across many vertebrate species, examples of hypomelanosis are rarely seen in chondrichthyans, with little insight into the potential effects on survival. Here, we report the first observation of abnormal skin pigmentation indicative of piebaldism in the Atlantic nurse shark Ginglymostoma cirratum, representing only the second reported case of skin aberrations for this species. This extremely rare observation is discussed in the broader context of fitness variation and long-term survival.

Urban sharks: residency patterns of marine top predators in relation to a coastal metropolis

Understanding and ultimately predicting how marine organisms will respond to urbanization is central for effective wildlife conservation and management in the Anthropocene. Sharks are upper trophic level predators in virtually all marine environments, but if and how their behaviors are influenced by coastal urbanization remains understudied. Here, we examined space use and residency patterns of 14 great hammerheads Sphyrna mokarran, 13 bull sharks Carcharhinus leucas, and 25 nurse sharks Ginglymostoma cirratum in proximity to the coastal metropolis of Miami, Florida, using passive acoustic telemetry. Based on the terrestrial urban carnivore literature, we predicted sharks would exhibit avoidance behaviors of areas close to Miami, with residency patterns in these urban areas increasing during periods of lower human activity, such as during nocturnal hours and weekdays, and that dietary specialists (great hammerhead) would exhibit comparatively lower affinity towards highly urbanized areas relative to dietary generalists (bull and nurse shark). However, we did not find empirical support for these predictions. Space use patterns of tracked sharks were consistent with that of ‘urban adapters’ (species that exhibit partial use of urban areas). Modeling also revealed that an unmeasured spatial variable was driving considerable shark residency in areas exposed to high urbanization. We propose several hypotheses that could explain our findings, including food provisioning from shore-based activities that could be attracting sharks to urban areas. Ultimately, the lack of avoidance of urban areas by sharks documented here, as compared to terrestrial carnivores, should motivate future research in the growing field of urban ecology.

Nurse sharks, space rockets and cargo ships: Metals and oxidative stress in a benthic, resident and large-sized mesopredator, Ginglymostoma cirratum

It is widely recognized that apex predators, such as large sharks with highly migratory behavior, are particularly vulnerable to pollution, mainly due to biomagnification processes. However, in highly impacted areas, mesopredator sharks with resident behavior can be as vulnerable as apex sharks. In this context, this study evaluated cadmium (Cd), mercury (Hg), lead (Pb), and rubidium (Rb) concentrations, as well as the potentially protective effects of selenium (Se) and the behavior of two non-enzymatic biomarkers, metallothionein (MT) and reduced glutathione (GSH), employing the Atlantic nurse shark Ginglymostoma cirratum as a study model and compared the results with other resident benthic sharks, as well as highly mobile apex sharks. Muscle tissue samples from 28 nurse sharks opportunistically sampled from the Brazilian Amazon Coast were analyzed. Lower metal concentrations were observed for Pb, Rb and Se in the rainy season, while statistically significant correlations between metals were observed only between Hg and Cd and Pb and Se. Molar ratio calculations indicate potential protective Se effects against Pb, but not against Cd and Hg. No associations between MT and the determined metals were observed, indicating a lack of detoxification processes via the MT detoxification route. The same was noted for GSH, indicating no induction of this primary cellular antioxidant defense. Our results indicate that benthic/mesopredator sharks with resident behavior are, in fact, as impacted as highly mobile apex predators, with the traditional detoxification pathways seemingly inefficient for the investigated species. Moreover, considering the studied population and other literature data, pollution should be listed as a threat to the species in future risk assessments.

Fossil dermal denticles reveal the preexploitation baseline of a Caribbean coral reef shark community

Preexploitation shark baselines and the history of human impact on coral reef-associated shark communities in the Caribbean are tpoorly understood. We recovered shark dermal denticles from mid-Holocene (∼7 ky ago) and modern reef sediments in Bocas del Toro, Caribbean Panama, to reconstruct an empirical shark baseline before major human impact and to quantify how much the modern shark community in the region had shifted from this historical reference point. We found that denticle accumulation rates, a proxy for shark abundance, declined by 71% since the mid-Holocene. All denticle morphotypes, which reflect shark community composition, experienced significant losses, but those morphotypes found on fast-swimming, pelagic sharks (e.g., families Carcharhinidae and Sphyrnidae) declined the most. An analysis of historical records suggested that the steepest decline in shark abundance occurred in the late 20th century, coinciding with the advent of a targeted shark fishery in Panama. Although the disproportionate loss of denticles characterizing pelagic sharks was consistent with overfishing, the large reduction in denticles characterizing demersal species with low commercial value (i.e., the nurse shark Ginglymostoma cirratum) indicated that other stressors could have exacerbated these declines. We demonstrate that the denticle record can reveal changes in shark communities over long ecological timescales, helping to contextualize contemporary abundances and inform shark management and ecology.

Environmental enrichment effects on the reproductive behavior of captive nurse sharks Ginglymostoma cirratum

Nurse sharks (Ginglymostoma cirratum, Ginglymostomatidae) are one of the most exhibited shark species in aquariums worldwide. However, in these locations, their reproductive success rate is frequently low. Considering that there is probably an olfactory mediation for nurse shark reproduction, and that environmental enrichment has a potentially positive effect on reproduction of captive animals, the present study aimed to evaluate whether the use of olfactory enrichment would stimulate olfactory-driven behaviors and consequently generate effects in the exhibition of reproductive behaviors by the species both in the short and long term. The study was divided into three phases (control, short-term enrichment and long-term enrichment), was conducted at two institutions with distinct husbandry and used aqueous extracts of basil leaves as olfactory enrichment. Eleven individuals were selected through focal sampling for behavioral observations with instantaneous recording, the total of 120 h of observation were divided into active and inactive periods. Results showed that basil-based olfactory enrichment was effective in increasing the occurrence of reproductive behaviors in both female and male nurse sharks. Additionally, the long-term results showed higher effects in males, which strengthen the theory of olfactory mediation of reproductive behavior in the species as individuals became aware of the sensory cues in the environment and performed more olfactory-driven reproductive behaviors. It is important to note that enrichment effects are different between sexes and therefore close monitoring and scheduling are essential to avoid over-stimulation or habituation to the enrichment.

Urban living influences the nutritional quality of a juvenile shark species

The field of marine urban ecology is a nascent, but growing area of research. An understanding of how urbanization may alter the diets and nutrition of marine species living in urbanized coastal habitats is limited. In the present study, we investigated the influence of urbanization on dietary patterns and nutritional quality of the nurse shark Ginglymostoma cirratum, a coastal epibenthic mesopredator. We tested the hypothesis that sharks sampled in urbanized areas (hereafter, ‘urban sharks’) would exhibit lower nutritional quality than individuals sampled in adjacent, but more pristine areas (hereafter ‘non-urban sharks’). To accomplish this, we compared plasma fatty acid profiles of juvenile nurse sharks in proximity to Miami, a large coastal city, within Biscayne Bay, Florida. Results revealed that urban sharks contained higher levels of plasma saturated and bacterial fatty acids compared to non-urban sharks. Urban sharks also exhibited lower proportions of essential fatty acids (i.e., highly unsaturated fatty acids, HUFAs), mainly due to low contributions of omega-6 HUFAs. These results suggest that urban sharks consumed lower-quality food resources than conspecifics in less impacted areas. The apparent poor nutritional quality of prey consumed by shark living in urban areas may have several long-term consequences on their health and growth.

Distribution and ontogenetic habitat shifts of reefassociated shark species in the northeastern Caribbean

Understanding how reef-associated sharks utilise coastal reef habitats throughout their ontogeny is essential for their effective management. In this study, we assessed the distribution of sharks in the northern Caribbean Netherlands (Saba, Saba Bank and St Eustatius) and ontogenetic shifts in habitat and depth use of the 2 most observed species: Caribbean reef shark Carcharhinus perezi and nurse shark Ginglymostoma cirratum. We used stereo baited remote underwater video (stereo-BRUV) surveys at 376 sites. A total of 126 shark sightings (6 species) were recorded, with C. perezi (n = 72) and G. cirratum (n = 42) most frequently observed. The probability of recording at least 1 shark per deployment ranged from 0.19 to 0.37 and is comparable with shark occurrences in the small number of other stereo-BRUV studies in the Wider Caribbean Region. Habitat type was the most important factor driving reef-associated shark occurrences, with the highest probability of observing C. perezi and G. cirratum in soft-coral habitat. Additionally, occurrences of C. perezi were significantly influenced by the management zone, with highest probabilities of occurrence in no-fishing zones. Almost all observed reef-associated sharks (95.6%) were juveniles, indicating that the study area may be a nursery area. Overall, both species were observed in deeper waters with increasing size, indicating ontogenetic shifts in depth use. Our findings imply that protected areas should not be limited to a single habitat or depth, but focus on protecting a large area with the range of habitats and depths necessary for reef-associated sharks to complete their life cycle.

Varying reef shark abundance trends inside a marine reserve: evidence of a Caribbean reef shark decline

Spatial comparisons of reef shark abundance inside and outside marine protected areas (MPAs) are common and generally report positive MPA effects, yet few studies have tracked abundance trends over long time periods. This is problematic because inside:outside comparisons at a single point in time cannot evaluate whether populations are declining. In Belize, the Caribbean reef shark Carcharhinus perezi is one of the most fished shark species and is more abundant inside MPAs. Although the relative abundance of C. perezi was stable inside Glover’s Reef Marine Reserve (GRMR) from 2001 to 2013, using standard baited remote underwater video station surveys, we document a decline in relative abundance inside the no-take marine reserve from 2009 to 2019. We used a negative binomial generalized linear model and model averaging to test the effect of year, depth, and water temperature on C. perezi and nurse shark Ginglymostoma cirratum relative abundance. While model-averaged results indicated a C. perezi decline, G. cirratum remained stable from 2009 to 2019. We hypothesize that the C. perezi decline is a result of fishing along the edge of GRMR, while G. cirratum stability is related to their behavior and nationwide protection. Given the dynamic nature of fisheries regulations, economic pressures, and site-specific environmental conditions, our results emphasize the need for standardized long-term monitoring of reef sharks inside and around MPAs globally.

Variation of body condition and plasma energy substrates with life stage, sex, and season in wild-sampled nurse sharks Ginglymostoma cirratum.

Reported here are the relationships among morphological (i.e., body condition) and biochemical (i.e., plasma concentrations of triglycerides, cholesterol, free fatty acids, and ketone bodies and ketone body ratios) parameters related to energy storage and use, as well as the variation of such parameters, for 107 free-ranging nurse sharks Ginglymostoma cirratum sampled off South Florida. Immature G. cirratum exhibited a higher variance in body condition, plasma free fatty acid concentrations and ketone body ratios compared to adults. Mature female G. cirratum had significantly higher body condition than mature males, driven by a seasonal increase in mature female body condition during the wet season. Mature male G. cirratum showed a decrease in the ketone body β-hydroxybutyric acid during the dry season. Taken together, this study provides a baseline assessment of body condition and internal physiological state for a data-poor marine species and demonstrates significant ontogenetic, sexual and seasonal variation in G. cirratum energetic state. As concluded by other studies of energy metabolism in free-ranging sharks, this research highlights the importance of considering intraspecific patterns and sampling context for inferring the drivers of variation.

A baited remote underwater video system (BRUVS) assessment of elasmobranch diversity and abundance on the eastern Caicos Bank (Turks and Caicos Islands); an environment in transition

The present study was undertaken to assess the diversity and abundance of elasmobranch fishes in coral reef and sand flat environments on the eastern Caicos Bank, with a view to informing marine spatial planning as the island of South Caicos and its environs transition to a tourism-based economy. Using baited remote underwater video systems (BRUVS), the nurse shark Ginglymostoma cirratum, Caribbean reef shark Carcharhinus perezi, spotted eagle ray Aetobatus narinari, southern stingray Hypanus americanus, lemon shark Negaprion brevirostris, tiger shark Galeocerdo cuvier, blacknose shark Carcharhinus acronotus, and great hammerhead shark Sphyrna mokarran were observed to use these waters, with G. cirratum and C. perezi being particularly abundant. Species diversity and overall abundance was greater in the reef environment than on the sand flats, but G. cirratum was equally abundant in both environments. Furthermore, even reef-associated species such as C. perezi were occasionally encountered on the flats a considerable distance from the reef. This indicates that although marine conservation efforts in the Turks and Caicos Islands should continue to focus on coral reef areas, less dramatic environments such as sand flats should not be ignored.

Serum Protein Analysis of Nurse Sharks.

Serum protein electrophoresis (EPH) is used to assess relative concentrations of blood proteins in clinical and biological studies. Serum EPH fractions have been determined for elasmobranchs using mammalian albumin, alpha 1-, alpha 2-, beta-, and gamma-globulin fractions, and have been deemed fractions 1 through 5, respectively. However, serum EPH fraction concentration reference intervals (RIs) have not been widely established for different elasmobranch species. In this study, RIs for fractions 1 through 5 were determined from 45 wild-caught Nurse Sharks Ginglymostoma cirratum (27 females and 23 males) in South Florida. Serum samples were isolated from whole blood following caudal venipuncture. Body condition was also measured in the field to assess the relative health of the individuals sampled. There was no relationship between body condition and serum EPH fraction concentrations. In addition, there was no difference in body condition or serum EPH fraction concentrations between females and males. Total solids and total protein values were significantly different (P<0.001). Nurse Shark serum EPH fraction 1 was found within the mammalian albumin migrating band distance and was negligible. Fraction 2 showed no peak in the mammalian alpha 1-globulin range. A thin, medium peak in the mammalian alpha 2-globulin range represented fraction 3. In the mammalian beta-globulin range, fraction 4 consisted of the majority of protein observed. It was represented by a smooth, broad peak. A short, medium broad peak in the mammalian gamma-globulin range represented fraction 5. The Nurse Shark serum EPH fraction RIs provided in this study may be utilized to clinically evaluate the health of Nurse Sharks in captivity and in the wild, and to compare the health of their populations around the world experiencing various anthropogenic stressors and other environmental impacts.

Network analysis reveals multispecies spatial associations in the shark community of a Caribbean marine protected area

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 633:105-126 (2020) - DOI: https://doi.org/10.3354/meps13158 Network analysis reveals multispecies spatial associations in the shark community of a Caribbean marine protected area Grace A. Casselberry1,*, Andy J. Danylchuk1, John T. Finn1, Bryan M. DeAngelis2, Adrian Jordaan1, Clayton G. Pollock3, Ian Lundgren4, Zandy Hillis-Starr3, Gregory B. Skomal5 1Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003, USA 2The Nature Conservancy, Narragansett, RI 02882, USA 3National Park Service, Christiansted, St. Croix 008020, USVI 4NOAA Fisheries, Pacific Islands Regional Office, Honolulu, HI 96818, USA 5Massachusetts Division of Marine Fisheries, New Bedford, MA 02744, USA *Corresponding author: gcasselberry@umass.edu ABSTRACT: Many shark species exhibit complex spatial ecology throughout their life histories, posing a challenge for conservation and management. Although most marine protected areas (MPAs) were originally established to protect less mobile organisms, protection of shark species from fishing and other impacts is possible if individuals exhibit high residency and site fidelity within the MPA boundaries. For this study, we used a fixed acoustic telemetry array to study the residency, habitat use, and interspecific space use among 4 shark species in Buck Island Reef National Monument (BIRNM), an MPA in St. Croix, US Virgin Islands. From June 2013 to May 2017, 11 nurse sharks Ginglymostoma cirratum, 6 lemon sharks Negaprion brevirostris, 13 Caribbean reef sharks Carcharhinus perezi, and 6 tiger sharks Galeocerdo cuvier were monitored in the array. Overall, residency was high for all species, with a mean residency index of 0.52 or higher for each species. Network analysis revealed complex inter- and intraspecific spatial associations among individuals. Community detection algorithms showed that G. cirratum and N. brevirostris frequently used the same areas in BIRNM, selecting for shallow sand and seagrass habitats near linear reefs, while G. cuvier and C. perezi had more individualized space use. C. perezi also exhibited ontogenetic shifts, developing individual territories and using deeper water with increasing body size. This work emphasizes the importance of MPA size, placement, and habitat composition when aiming to protect highly mobile species with potentially large home ranges and shifting space use throughout their life histories. KEY WORDS: Elasmobranchs · Spatial ecology · Acoustic telemetry · Network analysis · Marine protected area Full text in pdf format Supplementary material PreviousNextCite this article as: Casselberry GA, Danylchuk AJ, Finn JT, DeAngelis BM and others (2020) Network analysis reveals multispecies spatial associations in the shark community of a Caribbean marine protected area. Mar Ecol Prog Ser 633:105-126. https://doi.org/10.3354/meps13158 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 633. Online publication date: January 09, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Low lipid and urea effects and inter-tissue comparisons of stable isotope signatures in three nearshore elasmobranchs

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 579:233-238 (2017) - DOI: https://doi.org/10.3354/meps12264 NOTE Low lipid and urea effects and inter-tissue comparisons of stable isotope signatures in three nearshore elasmobranchs Oliver N. Shipley1,2,*, Karen J. Murchie3, Michael G. Frisk1, Edward J. Brooks2, Owen R. O’Shea2, Michael Power4 1School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11790, USA 2Shark Research and Conservation Program, The Cape Eleuthera Institute, Eleuthera, The Bahamas 3Daniel P. Haerther Center for Conservation and Research, John G. Shedd Aquarium, 1200 South Lake Shore Drive, Chicago, IL 60605, USA 4Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada *Corresponding author: oliver.shipley@stonybrook.edu ABSTRACT: Stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) is a common tool used to examine aspects of elasmobranch biology and ecology; however, accurate ecological interpretation of stable isotope values requires knowledge of lipid and urea dynamics, and the variable turnover rates of different tissue types. Here we examined lipid and urea dynamics and inter-tissue comparisons of stable isotope values in 3 nearshore elasmobranch species, the nurse shark Ginglymostoma cirratum, southern stingray Hypanus americanus, and the Atlantic chupare stingray Styracura schmardae. Chemical extraction had no significant effect on δ13C and δ15N values of nurse shark muscle, and southern and chupare stingray fin, suggesting negligible lipid and urea components associated with these tissues. For nurse sharks, δ13C values were higher in muscle compared to dermis and δ15N was lower. The causes of this variability are underpinned by the metabolic variability between tissue types, the physiological function of which remains undetermined. Finally, we observed a significant relationship between muscle and dermis δ13C and δ15N, providing the first inter-tissue isotopic correction for nurse sharks. The results provide insight into lipid and urea dynamics, and aid sample preparation and ecological interpretation of stable isotope data in these taxa. KEY WORDS: Stable isotope analysis · δ13C · δ15N · Elasmobranch · Shark · Stingray · Polar compounds Full text in pdf format Corrigendum PreviousCite this article as: Shipley ON, Murchie KJ, Frisk MG, Brooks EJ, O’Shea OR, Power M (2017) Low lipid and urea effects and inter-tissue comparisons of stable isotope signatures in three nearshore elasmobranchs. Mar Ecol Prog Ser 579:233-238. https://doi.org/10.3354/meps12264 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 579. Online publication date: September 14, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Complete mitochondrial genome of the nurse shark Ginglymostoma cirratum

We determined the complete mitochondrial genome sequence of nurse shark Ginglymostoma cirratum. The circular DNA of 16692 bp comprises 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, a non-coding control region and a non-coding origin of light strand replication with typical gene order of vertebrates. The nurse shark formed a well-supported clade that included whale shark Rhincodon typus and zebra shark Stegostoma fasciatum within the Orectolobiformes in a phylogenetic tree constructed with other published mitochondrial genomes of sharks.

Evasive mating behaviour by female nurse sharks, Ginglymostoma cirratum (Bonnaterre, 1788), in an equatorial insular breeding ground

ABSTRACT Mating events and aggregations of vulnerable nurse sharks Ginglymostoma cirratum were recorded in the insular protected area of Fernando de Noronha (FEN), Brazil, between April and August 2015. Female sharks were observed clustering in groups of up to 14 individuals in shallow water adjacent to the shore. Several evasive mating behaviours in the presence of males were noticed, including shoreward movement, positioning ventral side up at the sea surface with emerged pectoral and pelvic fins, body rolling and caudal fin thrashing. Fresh bite marks indicative of male courtship and coupling attempts were visible in female's pectoral and caudal fins. Altogether, the observed behaviours match previous reports of non-cooperative female nurse sharks during mating opportunities. An extended mating season coupled with a persistent use of inshore habitats result in nurse sharks being particularly vulnerable to human pressure during a most sensitive stage of their life cycle. The effective conservation of nurse shark populations from the western South Atlantic may thus depend on the protection of critical habitats where this species aggregates to reproduce. Explicitly addressing environmental requirements by vulnerable species in local management strategies is indispensable to ensure that human pressure, including ecotourism development, does not collide with stipulated conservation aims.

Reef sharks: recent advances in ecological understanding to inform conservation.

Sharks are increasingly being recognized as important members of coral-reef communities, but their overall conservation status remains uncertain. Nine of the 29 reef-shark species are designated as data deficient in the IUCN Red List, and three-fourths of reef sharks had unknown population trends at the time of their assessment. Fortunately, reef-shark research is on the rise. This new body of research demonstrates reef sharks' high site restriction, fidelity and residency on coral reefs, their broad trophic roles connecting reef communities and their high population genetic structure, all information that should be useful for their management and conservation. Importantly, recent studies on the abundance and population trends of the three classic carcharhinid reef sharks (grey reef shark Carcharhinus amblyrhynchos, blacktip reef shark Carcharhinus melanopterus and whitetip reef shark Triaenodon obesus) may contribute to reassessments identifying them as more vulnerable than currently realized. Because over half of the research effort has focused on only these three reef sharks and the nurse shark Ginglymostoma cirratum in only a few locales, there remain large taxonomic and geographic gaps in reef-shark knowledge. As such, a large portion of reef-shark biodiversity remains uncharacterized despite needs for targeted research identified in their red list assessments. A research agenda for the future should integrate abundance, life history, trophic ecology, genetics, habitat use and movement studies, and expand the breadth of such research to understudied species and localities, in order to better understand the conservation requirements of these species and to motivate effective conservation solutions.

Diet Reconstruction and Resource Partitioning of a Caribbean Marine Mesopredator Using Stable Isotope Bayesian Modelling

The trophic ecology of epibenthic mesopredators is not well understood in terms of prey partitioning with sympatric elasmobranchs or their effects on prey communities, yet the importance of omnivores in community trophic dynamics is being increasingly realised. This study used stable isotope analysis of 15N and 13C to model diet composition of wild southern stingrays Dasyatis americana and compare trophic niche space to nurse sharks Ginglymostoma cirratum and Caribbean reef sharks Carcharhinus perezi on Glovers Reef Atoll, Belize. Bayesian stable isotope mixing models were used to investigate prey choice as well as viable Diet-Tissue Discrimination Factors for use with stingrays. Stingray δ15N values showed the greatest variation and a positive relationship with size, with an isotopic niche width approximately twice that of sympatric species. Shark species exhibited comparatively restricted δ15N values and greater δ13C variation, with very little overlap of stingray niche space. Mixing models suggest bivalves and annelids are proportionally more important prey in the stingray diet than crustaceans and teleosts at Glovers Reef, in contrast to all but one published diet study using stomach contents from other locations. Incorporating gut contents information from the literature, we suggest diet-tissue discrimination factors values of Δ15N ≊ 2.7‰ and Δ13C ≊ 0.9‰ for stingrays in the absence of validation experiments. The wide trophic niche and lower trophic level exhibited by stingrays compared to sympatric sharks supports their putative role as important base stabilisers in benthic systems, with the potential to absorb trophic perturbations through numerous opportunistic prey interactions.

Identifying shark mating behaviour using three-dimensional acceleration loggers

Little is known about the reproductive strategies and mating behaviour of most sharks. Understanding mating behaviour is important as it can determine reproductive success and possibly rates of multiple paternity and fecundity. Additionally, some sharks appear to have specific habitat requirements for mating activities. We tested the utility of a 3-dimensional acceleration logger to identify mating events in free-living nurse sharks Ginglymostoma cirratum in an area where behav- iours can be observed directly, thus allowing corroboration of acceleration data. Loggers were attached to 4 adult females and were recovered after recording periods of 23.2 to 99.8 h (mean ± SD = 50.0 ± 35.1 h). We used acceleration data to classify several behaviours, including swimming, rest- ing, resting in a surge zone, and mating, with examples of each behaviour confirmed via direct obser- vation. Twenty-six mating events were inferred from acceleration data, ranging from 21 s to 20.1 min in duration (median = 2.22 min), with no events taking place during the nighttime hours between 23:00 and 07:00 h. Four events lasted longer than 9 min and took place during periods when logger- equipped sharks were not acoustically detected within the shallow study site. The similarity in mat- ing behaviours between this and some other species raises the possibility that accelerometry could be used to quantify mating in a variety of shark species. This is the first study to classify mating and other behaviours in free-living sharks from acceleration data.

Field hearing measurements of the Atlantic sharpnose shark Rhizoprionodon terraenovae

Field measurements of hearing thresholds were obtained from the Atlantic sharpnose shark Rhizoprionodon terraenovae using the auditory evoked potential method (AEP). The fish had most sensitive hearing at 20 Hz, the lowest frequency tested, with decreasing sensitivity at higher frequencies. Hearing thresholds were lower than AEP thresholds previously measured for the nurse shark Ginglymostoma cirratum and yellow stingray Urobatis jamaicensis at frequencies <200 Hz, and similar at 200 Hz and above. Rhizoprionodon terraenovae represents the closest comparison in terms of pelagic lifestyle to the sharks which have been observed in acoustic field attraction experiments. The sound pressure levels that would be equivalent to the particle acceleration thresholds of R. terraenovae were much higher than the sound levels which attracted closely related sharks suggesting a discrepancy between the hearing threshold experiments and the field attraction experiments.

First characterization of shark nursery habitat in the United States Virgin Islands: evidence of habitat partitioning by two shark species

Little is known of the diversity, demography, and essential fish habitat of sharks within the United States Virgin Islands (USVI) marine ecosystem. To examine species diversity and the relative abundance of elasmobranchs in this region, bottom-longline and hand-gear sampling was conducted in Fish Bay, St. John, USVI, from June 2004 to December 2005. In the 8 sampling trips during this period, 54 standardized longline sets caught 174 elasmobranchs comprising 5 species of sharks and 1 batoid. Overall catch per unit effort [ln(CPUE + 1) ± SE] was 1.83 ± 0.16 elasmobranchs 100 hooks–1 h–1. Lemon sharks Negaprion brevirostris had the highest relative abundance based on log-transformed CPUE data (0.98 ± 0.15), followed by blacktip sharks Carcharhinus limbatus (0.91 ± 0.18), southern stingrays Dasyatis americana (0.28 ± 0.08), nurse sharks Ginglymostoma cirratum (0.08 ± 0.05), blacknose sharks Carcharhinus acronotus (0.06 ± 0.04) and the Caribbean sharpnose Rhizoprionodon porosus (0.03 ± 0.03). The relative abundance of all species was significantly higher in the summer (2.6 ± 0.2) than during the winter (1.1 ± 0.2). For the blacktip (N = 89 captures of 74 individuals) and lemon (N = 66, 48 individuals) sharks, which comprised the bulk of the catch, mean fork length (± SE) was 51.9 ± 0.63 cm and 59.9 ± 1.2 cm, respectively, representing primarily neonatal and young-of-the-year life stages. The recapture rates for blacktip and lemon sharks were 21% and 29%, respectively, and nearly all recaptures occurred within the bay, indicating a high degree of site fidelity. Capture information and limited acoustic tracking provided evidence of spatial and temporal habitat partitioning by these 2 shark species within the bay. Although the CPUE of both species was highest over shallow (<1 m) seagrass substrate, lemon sharks were found and tracked exclusively on shallow, mangrove-fringed seagrass habitat, while blacktip sharks utilized a wider area of the bay. Fish Bay was determined to provide important nursery habitat for young juvenile lemon and blacktip sharks in the USVI.