White sharks and cephalopod prey : indicators of habitat use?

The stomach contents of White Sharks (Carcharodon carcharias) caught in large mesh gillnets off the KwaZulu-Natal coast of South Africa were examined for prey remains during routine biological necropsies. Of 220 White Sharks with prey remains in their stomachs sampled between 1983 and 2008, cephalopod beaks, which are highly digestion resistant, were found in 24. This sample was split according to predator size to investigate whether these prey remains could be used to test the hypothesis that smaller individuals [2.5 m TL), which may be a proxy for habitat use. These preliminary results supported the hypothesis in that the cephalopods from small sharks were composed almost exclusively of coastal and benthic species typical of the continental shelf, such as octopods and sepiids, and coastal pelagic prey, such as loliginid squids. Cephalopod prey of large sharks were dominated by mesopelagic and oceanic prey (e.g. Ancistrocheirus, Octopoteuthis, and Ommastrephidae), with few coastal taxa. This suggests that larger sharks are using deeper offshore waters to a greater extent than smaller individuals, supporting the ¢ndings from tagging research on these apex predators. This study has shown the potential of stomach content analyses to provide an alternative approach to studying habitat use by large predators, although there are some potential pitfalls of such investigations