Journal of the Marine Biological Association of the UK



Research Article

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


James A.  Estrada a1p1, Aaron N.  Rice a1p2a4c1, Molly E.  Lutcavage a2a5 and Gregory B.  Skomal a3
a1 Boston University Marine Program, Marine Biological Laboratory, Woods Hole, MA 02543, USA
a2 New England Aquarium, Central Wharf, Boston, MA 02110, USA
a3 Massachusetts Division of Marine Fisheries, Martha's Vineyard Research Station, Vineyard Haven, MA 02568, USA
a4 Division of Fishes, Department of Zoology, Field Museum of Natural History, Chicago, IL 60605, USA
a5 Department of Zoology, University of New Hampshire, Durham, NH 03824, USA

Article author query
estrada ja   [PubMed][Google Scholar] 
rice an   [PubMed][Google Scholar] 
lutcavage me   [PubMed][Google Scholar] 
skomal gb   [PubMed][Google Scholar] 

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.

(Received June 19 2003)
(Accepted October 28 2003)


Correspondence:
c1 arice@uchicago.edu
p1 Carteret Community College, Morehead City, NC 28557, USA
p2 Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA