Diet of the blacktip shark (Carcharhinus limbatus) in the northwestern Gulf of Mexico

Abstract

The stomach contents of 90 blacktip sharks (Carcharhinus limbatus) caught in the northwestern Gulf of Mexico were examined. Stomach contents were identified to the lowest possible taxon, and quantified using percent weight, percent number, percent frequency of occurrence, and percent index of relative importance (IRI). Teleosts were the dominant prey group (98.95% IRI), although most were unidentified (61.70% IRI). Of identified teleost species, Atlantic croaker (Micropogonias undulatus) (28.43% IRI), and Gulf menhaden (Brevoortia patronus) (2.31% IRI) were the most important. Crustaceans (0.65% IRI), mollusks (0.46% IRI), and elasmobranchs (0.03% IRI) formed a minor component of the diet. Suspected shrimp fishery discards were found in 11% of stomachs, highlighting the potential importance of this food source for blacktip sharks. Diet composition did not differ between male and female sharks, but did between juveniles and adults. Juvenile shark diets had greater proportions of unidentified teleost, Clupeidae and Penaeidae, while adult diets had greater proportions of Sciaenidae, Ariidae and cephalopods. Our results were similar, although not identical to, other studies of blacktip shark diets in the northwestern Gulf of Mexico. Of note is our finding of mantis shrimp (Squilla empusa), a species previously unreported in blacktip shark stomach contents. This new finding, the high importance of unidentified teleost, and the lack of asymptote in the prey accumulation curve emphasize the need for further study of the blacktip shark diet in the northwestern Gulf of Mexico.

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