DIET OF COMMON DOLPHINS (DELPHINUS-DELPHIS) OFF THE SOUTH-EAST COAST OF SOUTHERN AFRICA - OPPORTUNISM OR SPECIALIZATION

A total of 297 common dolphin (Delphinus delphis) stomachs was used fo r these diet analyses. AH originated from common dolphins incidentally captured in Natal, where their occurrence is strongly associated with an annual, northward fish migration, the sardine run, along the east coast. Thirty-six fish and four cephalopod prey species were identifie d. Though 86.9% by weight of the diet was made up of only five prey sp ecies, common dolphins appear to feed opportunistically, their diet re flecting local prey abundance and availability. Prey were primarily sm all, easily-caught, pelagic shoaling species, with the main prey being South African pilchard (Sardinops ocellatus). Although pilchard domin ated the diet between 1974 and 1992, there were marked annual and seas onal fluctuations in dietary composition, reflecting changes in prey a vailability and abundance. There were clear differences in the contrib ution of particular prey species to the diet of different sex and size groups, with strong evidence for resource partitioning between groups . The influence of the annual 'sardine run', and the fish predators as sociated with it, on the diet, feeding biology and distribution of com mon dolphins is discussed.