Prey spectrum of breeding sooty shearwaters (Puffinus griseus) in New Zealand

Prey remains from sooty shearwater (Puffinus griseus Gmelin, 1792) regurgitates, stomachs, and gizzards, were collected from four breeding colonies in southern New Zealand. We found a wide range of prey species (minimum 39 species of 35 genera), the most important of which were crustaceans (particularly euphausiid krill and hyperiid amphipods), cephalopods (notably arrow squid), fishes, and salps. Malacostracans (krill, amphipods, and decapods) were the predominant taxa of prey in both diversity and frequency of occurrence. Regurgitates were easily obtained from harvested chicks and provided the greatest range of prey remains (36 of the 39 species identified). However, these regurgitates comprised only 29% of the total number of samples collected. Fish, malacostracan, and salp prey ranged from 4 to 170 mm in size, whereas total lengths of squid ranged from 50 to 535 mm. Based on size and mass, the largest squid were undoubtedly scavenged, possibly in association with commercial fishers. The geographical distribution of prey species indicate that most sooty shearwaters breeding near Stewart Island forage in waters lying between the Subtropical and Polar Fronts. Our results suggest that the abundance of krill, the impact of fisheries and the influence of climate perturbations on prey species may play important roles in sooty shearwater breeding and survival.