Large numbers of seabirds frequent New Zealand commercial fishing waters. The accurate determination of the taxa of seabirds captured in New Zealand fisheries is vital for examining the potential threat to population viability posed by incidental fisheries captures, and to help reduce future captures. The assessment of the age-class, sex and provenance of captured individuals requires autopsy in the majority of cases.
Between 1 October 2007 and 30 September 2008 (the 2007/08 fishing year), a total of 251 seabirds comprising 20 taxa were incidentally killed as bycatch and returned for autopsy by on-board government observers. Birds were returned from longline, trawl and setnet vessels. Seabirds returned during the 2007/08 fishing year were dominated numerically by two species (sooty shearwater Puffinus griseus and white-chinned petrel Procellaria aequinoctialis) which, combined, accounted for 54% of all specimens.
Of birds returned from longline fisheries, 46% had injuries consistent with being hooked or entangled in the bill or throat, with albatross taxa comprising 70% of specimens killed in this way.
In contrast, 86% of all returns from trawl fisheries were killed through entanglement in the net, of which 76% were non-albatross taxa. Warp interaction was the likely cause of death in only 14% of trawl specimens, of which 92% were albatross taxa. Mean fat scores were generally higher in birds from the 2007/08 fishing year than in most previous years, although for all but one of the six most commonly returned species (grey petrel Procellaria cinerea), mean fat scores were lower in 2007/08 than in both 2005/06 and 2006/07.
Seabirds returned from the 2007/08 fishing year, and from trawl fisheries in particular, continued to show clear size-related differences in the likely cause of death, and offal appears to continue to be an attractant for many taxa, particularly in trawl fisheries.