Diets of coastal bottlenose dolphins from the US mid-Atlantic coast differ by habitat

We recorded 31 species in the stomachs of 146 coastal bottlenose dolphins (Tursiops truncatus) from North Carolina, U.S.A. Sciaenid fishes were the most common prey (frequency of occurrence = 95%). By mass, Atlantic croaker (Micropogonias undulatus) dominated the diet of dolphins that stranded inside estuaries, whereas weakfish (Cynosicon regalis) was most important for dolphins in the ocean. Inshore squid (Loligo sp.) was eaten commonly by dolphins in the ocean, but not by those in the estuaries. There was no significant pattern in prey size associated with dolphin demography, but the proportion of the diet represented by croaker was higher for males than for females, and mature dolphins ate more croaker than did juveniles. Dietary differences between dolphins that stranded in the estuaries and those that stranded on ocean beaches support the hypothesis that some members of the Population inhabit the ocean primarily while others reside principally in estuaries. The overwhelming majority of prey were soniferous species (75% of numerical abundance), which is consistent with the hypothesis that bottlenose dolphins use passive listening to locate noise-making fishes. However, spatiotemporal patterns in consumption of Sciaenid fishes did not coincide with their spawning, which is when peak sound production is thought to occur.