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Brooks E.J.,Cape Eleuthera Institute | Brooks A.M.L.,Cape Eleuthera Institute | Williams S.,Cape Eleuthera Institute | Jordan L.K.B.,Microwave Telemetry Inc. | And 4 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2015

Deep-sea chondrichthyans, like many deep-water fishes, are very poorly understood at the most fundamental biological, ecological and taxonomic levels. Our study represents the first ecological investigation of deep-water elasmobranch assemblages in The Bahamas, and the first assessment of species-specific resilience to capture for all of the species captured. Standardised deep-water longline surveys (n=69) were conducted September to December 2010 and 2011 between 472. m and 1024. m deep, resulting in the capture of 144 sharks from 8 different species. These included the Cuban dogfish, Squalus cubensis, the bigeye sixgill shark, Hexanchus nakamurai, the bluntnose sixgill shark, Hexanchus griseus, the smooth dogfish, Mustelus canis insularis, the roughskin dogfish, Centroscymnus owstoni, Springer[U+05F3]s sawtail catshark, Galeus springeri and the false catshark, Pseudotriakis microdon. Preliminary genetic analysis indicated two or more species of gulper sharks, Centrophorus spp.; however, for the present study they were treated as a single species complex. Water depth and distance from the rocky structure of the Exuma Sound wall were inversely correlated with species richness, whereas seabed temperature was directly correlated with species richness. These variables also had a significant influence on the abundance and distribution of many species. Expanded depth ranges were established for S. cubensis and H. nakamurai, which, in the case of S. cubensis, is thought to be driven by thermal preferences. At-vessel mortality rates increased significantly with depth, and post-release mortality was thought to be high for some species, in part due to high post-release predation. This study highlights the importance of utilising strategic geographic locations that provide easy access to deep water, in combination with traditional expedition-based deep-ocean science, to accelerate the acquisition of fundamental ecological and biological insights into deep-sea elasmobranchs. © 2015 Elsevier Ltd.

Howey-Jordan L.A.,Microwave Telemetry Inc. | Brooks E.J.,Cape Eleuthera Institute | Abercrombie D.L.,Abercrombie and Fish | Jordan L.K.B.,Microwave Telemetry Inc. | And 4 more authors.
PLoS ONE | Year: 2013

Oceanic whitetip sharks (Carcharhinus longimanus) have recently been targeted for conservation in the western North Atlantic following severe declines in abundance. Pop-up satellite archival tags were applied to 11 mature oceanic whitetips (10 females, 1 male) near Cat Island in the central Bahamas 1-8 May 2011 to provide information about the horizontal and vertical movements of this species. Another large female was opportunistically tagged in the U.S. Exclusive Economic Zone (EEZ). Data from 1,563 total tracking days and 1,142,598 combined depth and temperature readings were obtained. Sharks tagged at Cat Island stayed within 500 km of the tagging site for ~30 days before dispersing across 16,422 km2 of the western North Atlantic. Maximum individual displacement from the tagging site ranged from 290-1940 km after times at liberty from 30-245 days, with individuals moving to several different destinations (the northern Lesser Antilles, the northern Bahamas, and north of the Windward Passage). Many sharks returned to The Bahamas after ~150 days. Estimated residency times within The Bahamas EEZ, where longlining and commercial trade of sharks is illegal, were generally high (mean = 68.2% of time). Sharks spent 99.7% of their time shallower than 200 m and did not exhibit differences in day and night mean depths. There was a positive correlation between daily sea surface temperature and mean depth occupied, suggesting possible behavioral thermoregulation. All individuals made short duration (mean = 13.06 minutes) dives into the mesopelagic zone (down to 1082 m and 7.75°C), which occurred significantly more often at night. Ascent rates during these dives were significantly slower than descent rates, suggesting that these dives are for foraging. The sharks tracked appear to be most vulnerable to pelagic fishing gear deployed from 0-125 m depths, which they may encounter from June to October after leaving the protected waters of The Bahamas EEZ. © 2013 Howey-Jordan et al.

Hussey N.E.,University of Windsor | Chapman D.D.,Marine Conservation Institute | Donnelly E.,University of Windsor | Abercrombie D.L.,Abercrombie and Fish | Fisk A.T.,University of Windsor
Limnology and Oceanography: Methods | Year: 2011

Analyzing stable isotopes (SI: δ 15N and δ 13C) in a new tissue requires rigorous testing before its general application in examining aspects of animal ecology. Shark fin provides a novel, minor invasive source material, which is important considering the conservation status of many large sharks. Fin, however, is not a single tissue but composed of multiple tissues, primarily skin and cartilage. This may complicate the interpretation of SI, as fin can be sampled from multiple fins and different regions of a fin from an individual. Here, we examined the variation in δ 15N and δ 13C with sample location on the anal fin of Caribbean reef sharks (Carcharhinus perezi). Values of δ 15N and δ 13C were highly correlated across sampling locations indicating that mean population or size class fin SI data would be reliable. At the individual level, large variation in δ 15N and δ 13C between anal fin sampling locations indicates that the varying proportional contributions of tissues would complicate individual level analyses. For three pelagic shark species, dorsal fin δ 13C values were consistently higher than δ 13C muscle tissue values, identifying tissue-specific diet discrimination factors. This would confound multiple tissue studies that assume that SI values across tissues will be equal if the animal is in equilibrium with its diet. Proposed sampling protocols for fin material will negate many of these issues, but caution is warranted for comparisons of SI data between shark fin and other tissues or across species until the isotope dynamics of fin have been experimentally validated. © 2011, by the American Society of Limnology and Oceanography, Inc.

Madigan D.J.,State University of New York at Stony Brook | Brooks E.J.,Cape Eleuthera Institute | Bond M.E.,State University of New York at Stony Brook | Gelsleichter J.,University of North Florida | And 4 more authors.
Marine Ecology Progress Series | Year: 2015

Identifying the driving forces behind oceanic pelagic shark movements is key to a better understanding of their life history. Some oceanic pelagic shark species have been shown to aggregate in specific regions to mate and/or exploit abundant food resources. The oceanic whitetip shark Carcharhinus longimanus, a subtropical, ectothermic, oceanic pelagic shark that has experienced severe population declines, aggregates seasonally around Cat Island (CI) in The Bahamas. Large pelagic teleosts (e.g. billfish, tunas, and dolphinfish) are abundant in this region and oceanic whitetips are anecdotally reported to feed heavily on recreationally caught teleosts. However, it was unknown whether feeding habits at CI substantially differ from longer-term feeding habits. We used tag-recapture to assess site-fidelity of adult oceanic whitetips to CI and stable isotope analysis (SIA) of 2 different tissues (blood plasma and white muscle) to compare short- and long-term feeding patterns. The relatively high recapture rate (20.3%) confirmed that individual whitetips exhibit site-fidelity to CI. The aggregation consisted of adult individuals; females were more common, more than half were gravid, and no physical or behavioral evidence of mating or parturition was observed at CI. SIA-based Bayesian mixing model estimates of short-term (near CI) diets showed more large pelagic teleosts (72%) than in long-term diets (47%), showing a spatiotemporal difference in oceanic whitetip feeding habits. This suggests that availability of large teleost prey is a possible mechanism underpinning site-fidelity and aggregation of whitetips at CI. These results provide insight into the function of one of the last known aggregations of this once-abundant top predator. © Inter-Research 2015.

Fields A.T.,State University of New York at Stony Brook | Abercrombie D.L.,Abercrombie and Fish | Eng R.,State University of New York at Stony Brook | Feldheim K.,Pritzker Laboratory for Molecular Systematics and Evolution | Chapman D.D.,State University of New York at Stony Brook
PLoS ONE | Year: 2015

There is a growing need to identify shark products in trade, in part due to the recent listing of five commercially important species on the Appendices of the Convention on International Trade in Endangered Species (CITES; porbeagle, Lamna nasus, oceanic whitetip, Carcharhinus longimanus scalloped hammerhead, Sphyrna lewini, smooth hammerhead, S. zygaena and great hammerhead S. mokarran) in addition to three species listed in the early part of this century (whale, Rhincodon typus, basking, Cetorhinus maximus, and white, Carcharodon carcharias). Shark fins are traded internationally to supply the Asian dried seafood market, in which they are used to make the luxury dish shark fin soup. Shark fins usually enter international trade with their skin still intact and can be identified using morphological characters or standard DNA-barcoding approaches. Once they reach Asia and are traded in this region the skin is removed and they are treated with chemicals that eliminate many key diagnostic characters and degrade their DNA ("processed fins"). Here, we present a validated mini-barcode assay based on partial sequences of the cytochrome oxidase I gene that can reliably identify the processed fins of seven of the eight CITES listed shark species. We also demonstrate that the assay can even frequently identify the species or genus of origin of shark fin soup (31 out of 50 samples). © 2015 PLOS ONE.

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