Abstract
Stomach contents of 63 Hector's dolphins (Cephalorhynchus hectori) were collected between 1984 and 2006 from throughout New Zealand to provide the first quantitative assessment of prey composition. Twenty-nine taxa were identified. Those most commonly consumed were red cod (Pseudophycis bachus), ahuru (Auchenoceros punctatus), arrow squid (Nototodarus sp.), sprat (Sprattus sp.), sole (Peltorhamphus sp.), and stargazer (Crapatalus sp.). By mass, these six species contributed 77% of total diet. Red cod contributed the most in terms of mass (37%), while ahuru and Hector's lanternfish (Lampanyctodes hectoris) were consumed in large numbers. Prey ranged from <1cm to >60cm in total length, but the majority of prey items were <10cm long, indicating that for some species, juveniles were targeted. Diets of dolphins from South Island east and west coasts were significantly different, due largely to javelinfish (Lepidorhynchus denticulatus) being of greater importance in west coast stomachs, and a greater consumption of demersal prey species in the east. The feeding ecology of Hector's dolphin is broadly similar to that of other Cephalorhynchus species. Hector's dolphin is shown to feed on species from throughout the water column, and differences in diet between populations are thought to reflect prey availability.