The diet of long-beaked common dolphin Delphinus capensis, dusky dolphin Lagenorhynchus obscurus, Burmeister’s porpoise Phocoena spinipinnis, and bottlenose dolphin Tursiops truncatus, was determined based on 281 stomach contents collected along the Peruvian central coast and San Juan de Marcona in the period 1987-1993. Counts of otoliths, squid beaks and some other remains were used to estimate frequency of occurrence and prey percentage of composition (PC). Long-beaked common dolphins (n=117) fed mainly on fish (98.71% of preys), the remainder was composed of squids and crustaceans: Peruvian anchovies Engraulis ringens (PC= 71.14%), Vincigerria lucetia (7.89%), Lampanictus parvicauda (6.77%), Merluccius gayi (4.49%), Odontesthes regia (3.54%), Mictophum nitidulum (2.62%) and Trachurus picturatus (1.42%). Dusky dolphins (n=66) consumed E. ringens (49.8%, 16.9%), L. parvicauda (23.6%, 0.1%), T. picturatus (17.1%, 0%), Normachthys crockery (0%, 76.4%), V. lucetia (3.5%, 0.1%), and Sardinops sagax (2.8%, 0 %) off the central Peruvian coast and San Juan de Marcona, respectively. In the same areas, Burmeister’s porpoise (n=67) fed on anchovies (90.37%, 81.89%), O. regia (6.64%, 0%), Anchoa sp. (1.13%, 0%), N. crockery (0%, 8.53%) and M. gayi (0.65%, 8.4%). Bottlenose dolphins (n=22) consumed L. parvicauda (39.24%), Sphiraena sp. (13.48%), S. sagax (13.31%), Prionotus sp. (9.59%), M. gayi (7.43%), T. picturatus (4.41%) and E. ringens (4.06%). The use of the Shannon & Wiener, Levins and Czekanowski’s indexes in combination with the feeding patterns of the sampled species indicated an opportunistic feeding strategy with respect to their preys. The four cetacean species studied are predators of both pelagic and mesopelagic large schooling fish species, and demonstrate no selectivity towards prey species but towards social behaviour and habitat. An average linkage cluster analysis showed high levels of similarity in the diets of the studied cetaceans. This low diversification and a high degree of overlap in trophic niches is probably related to the high productivity of the Peruvian upwelling ecosystem. |
