Estimation of the incidental capture of seabird species in commercial fisheries in New Zealand waters, 2002/03

Ministry of Fisheries observers reported 595 seabird captures from observed fishing operations in 2002–03: 265 from observed trawl fishing operations (67% landed dead); 113 from tuna (Thunnus spp.) longlining operations (83% landed dead); and 217 from ling (Genypterus blacodes) longline operations (95% dead). The trawl-caught seabirds were from at least eight target fisheries, four of which had less than 50 observed tows. Observed squid (Nototodarus spp.) and hoki (Macruronus novaezelandiae) trawl fisheries accounted for 87% of observed trawl-caught seabirds.
Incident rates (expressed as the percent of observed fishing operations with seabird captures) for longline fisheries in 2002–03 were highest in chartered albacore tuna (T. alalunga) sets in northern waters (17%), compared with 10% for the observed chartered southern bluefin tuna (T. maccoyii) longlines off the southwest coast of the South Island and 9% of observed ling sets. About 2% of observed hoki tows in the main fishery areas had incidental captures, compared with 9% of observed squid trawls.
Mean seabird catch rates were estimated for the main fisheries with observed seabird captures: 0.048 seabirds per 1000 hooks (s.e = 0.010) for the chartered southern bluefin tuna fishery; 0.096 seabirds per 1000 hooks (s.e. = 0.017) for the chartered albacore effort; for ling longlines, mean catch rates ranged from 0.013 seabirds per 1000 hooks (s.e. = 0.002) in LIN 4 to 0.079 (s.e. = 0.032) in LIN 3; for hoki fisheries, 0.007 seabirds per tow (s.e. = 0.008) at Cook Strait to 0.185 (s.e. = 0.103) at the Puysegur fishery; and for squid fisheries, 0.035 seabirds per tow (s.e. = 0.011) at Puysegur and 0.198 (s.e. = 0.032) off the Stewart-Snares shelf.
Total estimates are provided for the main fisheries: 42 seabirds (c.v. = 6%) were estimated caught on chartered southern bluefin tuna longlines; 94 seabirds (c.v. = 8%) were estimated from chartered albacore effort; 543 seabirds (c.v = 10%) for ling autoline fisheries in areas LIN 4, LIN 5, and LIN 6 compared with 412 seabirds (c.v. = 8%) for the six observed vessels by area and season; 269 seabirds (c.v. = 23%) for hoki fisheries at Puysegur, Sub-Antarctic, and west coast South Island; and 841 seabirds (c.v. = 12%) for squid trawl fisheries at Puysegur, Stewart-Snares shelf and SQU 6T. Numbers are given for seabirds in total, rather than individual taxa, because of problems extrapolating by seabird species over a fishery.
In fisheries for which the observer coverage was < 10% of the total effort in a season or fishing year, the number of observed seabirds are reported: one seabird from the domestic tuna fishery in southern waters; 11 seabirds from LIN 3 autoline fishery; 76 seabirds from trawl fisheries (including hoki and squid fisheries with less than 10% observer coverage).
Of the reported captures, 438 were returned for identification and represented nine albatross and ten petrel taxa, one of which was previously unrecorded as caught during observed fishing operations: white-headed petrel (Pterodroma lessoni). About 75% of the seabirds returned for identification comprised four taxa: 28% were white-chinned petrels (Procellaria aequinoctialis), 18% were sooty shearwaters (Puffinus griseus), 16% were white-capped albatrosses (Thalassarche steadi), and 13% were white-chinned petrels (Procellaria aequinoctialis).