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Size related dietary shifts of Epinephelus marginatus in a western Mediterranean littoral ecosystem: An isotope and stomach content analysis

Lookup NU author(s): Professor Nick Polunin


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The diet of the dusky grouper Epinephelus marginatus, from the Balearic Islands, western Mediterranean, consisted primarily of crustaceans, molluscs and fishes, but diet composition varied with body size. The smaller dusky groupers (<300 mm LT) fed primarily on crustaceans, and particularly on brachyurans, which accounted for 46% of the prey identified. As dusky groupers grew, cephalopods became increasingly important and constituted 10 to 40% of the prey identified in subadult and adult specimens. The largest dusky groupers fed primarily on fishes that represented 40.9% of prey identified. These shifts in diet were accompanied by a positive selection of increasingly large prey and by an expansion of trophic niche. δ15N values of dusky grouper white muscle ranged from 8.8 to 13.1‰ and 71% of the variation in δ15N was explained by differences in dusky grouper size. δ13C values ranged from -17.9 to -15.9‰, and no significant body size effect on δ13C was detected. Stomach content and 13C values indicated that from 1 year old, the diet of E. marginatus was based on the benthic food web. The enrichment in δ15N registered from juvenile to large males was c. 3.8‰. Overall, there was good agreement between gut content and stable isotope data indicating that the latter may be useful as a tool in trophic studies in marine protected areas where sampling for fishes is not allowed. © 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.

Publication metadata

Author(s): Renones O, Polunin NVC, Goni R

Publication type: Article

Publication status: Published

Journal: Journal of Fish Biology

Year: 2002

Volume: 61

Issue: 1

Pages: 122-137

ISSN (print): 0022-1112

ISSN (electronic): 1095-8649

Publisher: Wiley-Blackwell Publishing Ltd.


DOI: 10.1006/jfbi.2002.2024


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