Abstract: Species-specific diet analysis is fundamental for the study of many ecological processes. In the marine environment, however, the direct observation of foraging such as ingestion events can be difficult, which is why indirect methods have been developed. Between 2002 and 2009, we used a non-invasive and easily applicable method to investigate the prey composition of a piscivorous predator near the surface. Prey fish shed scales when hunted and caught by common bottlenose dolphins (Tursiops truncatus) that were then collected from aboard a small vessel in a Greek embayment. A total of 1,227 fish scales related to surface feeding events of bottlenose dolphins were gathered during 257 predatory events on 185 different days. After fixation and comparison with a reference catalogue, it was possible to determine the prey species. Of the collected scales, 99.8% belonged to two species of Clupeidae, namely European pilchard (Sardina pilchardus) and round sardinella (Sardinella aurita). The result can be related to the abundant availability of epipelagic planktivorous fishes in the eutrophic waters of the Gulf of Ambracia. Since surface feeding is not reported for bottlenose dolphins from the wider Mediterranean Sea, the adaptability of this species to local feeding conditions is discussed. Finally, we discuss the advantages and shortcomings of fish scale collection compared to other indirect methods for the identification of prey species, most of which have some limitations and, thus, may complement each other.

Key Words: diet analysis, fish scales, bottlenose dolphins, Tursiops truncatus, prey identification, sardine
Document Type: Article
DOI: 10.1578/AM.42.1.2016.63
Page Numbers: 63-73