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Predicting trophic position in sharks of the north-west Atlantic Ocean using stable isotope analysis

Published online by Cambridge University Press:  08 January 2004

James A. Estrada
Affiliation:
Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA Carteret Community College, Morehead City, NC 28557, USA
Aaron N. Rice
Affiliation:
Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA Division of Fishes, Department of Zoology, Field Museum of Natural History, Chicago, IL 60605, USA Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA
Molly E. Lutcavage
Affiliation:
New England Aquarium, Central Wharf, Boston, MA 02110, USA Department of Zoology, University of New Hampshire, Durham, NH 03824, USA
Gregory B. Skomal
Affiliation:
Massachusetts Division of Marine Fisheries, Martha's Vineyard Research Station, Vineyard Haven, MA 02568, USA

Abstract

Trophic positions (TP) were estimated for the blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and basking shark (Cetorhinus maximus) using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). The basking shark had the lowest TP (3·1) and δ15N value (10·4‰), whereas the thresher shark had the highest values (4·5, 15·2‰). Mako sharks showed considerable variation in TP and isotopic values, possibly due to foraging from both inshore and offshore waters. Thresher sharks were significantly more enriched in δ15N than blue sharks and mako sharks, suggesting a different prey base. The δ13C values of thresher sharks and mako sharks varied significantly, but neither was significantly different from that of blue sharks. No statistical differences were found between our TP estimations and those derived from published stomach contents analyses, indicating that stable isotope data may be used to estimate the trophic status of sharks.

Type
Research Article
Copyright
2003 Marine Biological Association of the United Kingdom

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