Stomach content analysis of stranded bottlenose dolphins ( Tursiops truncatus) in South Carolina

Abstract

Stomach contents of 136 bottlenose dolphins (Tursiops truncatus ) stranded dead or incidentally caught in South Carolina between 2000 and 2006 were examined. Eighty-two bottlenose dolphin stomachs contained food items and were the basis for this study. Primary diet components included fish and cephalopods with fish alone or in some combination with other prey types found in 89% (n=73) of the stomachs examined. Squid was the sole dietary component in 11% (n=9) of the stomachs. Forty-two prey species representing 24 families were identified. Dolphins in this study fed predominantly on smaller-sized benthic and demersal fish species. The relative importance of prey species in the dolphin diet was measured in terms of abundance and frequency of occurrence. Diets were primarily comprised of members of the family Sciaenidae with star drum (Stellifer lanceolatus) the most abundant species quantitatively. Brief squid (Lolliguncula brevis) was the most frequently observed prey species. Comparisons among the stomachs in this study were made to delineate any spatiotemporal variations in prey preference as well as to determine if the stomach contents of dead, stranded bottlenose dolphins were representative of living bottlenose dolphin populations. Overall, dolphins that appeared to have died from natural causes consumed similar species of fish and squid to those that exhibited signs of human interaction but appeared otherwise healthy. Many of the prey species consumed by dolphins in both categories were established by-catch species of the local commercial shrimp trawling industry. This study represents the first quantitative analysis of prey species comprising the diet of bottlenose dolphins in South Carolina.