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    Estimation of the incidental capture of seabird species in commercial fisheries in New Zealand waters, 2001/02

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    Número de documento:
    S.J. Baird (New Zealand)
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    Ministry of Fisheries observers reported 851 seabird captures from observed fishing operations in 2001–02: 324 from observed trawl fishing operations (87% landed dead); 167 from tuna (Thunnus spp.) longlining operations (87% landed dead); and 330 from ling (Genypterus blacodes) longline operations (93% dead). Observers recorded another 104 seabirds from unobserved parts of ling longline hauls. Observed squid (Nototodarus spp.) and hoki (Macruronus novaezelandiae) trawl fisheries accounted for 87% of observed trawl-caught seabirds.
    Demersal and surface longline fisheries had the highest incident rates (numbers of seabirds per observed fishing operation) in 2001–02, with seabirds reported caught from 26% of observed domestic tuna sets in northern waters, 22% of observed chartered Japanese longlines off the southern west coast of the South Island, and 10% of observed ling sets. About 1% of observed hoki tows in the main fishery areas had incidental captures, compared with 9% of observed squid trawls. Observed incident rates in at least seven other trawl fisheries ranged from <1 % in orange roughy (Hoplostethus atlanticus) tows to 7% in silver warehou (Seriolella punctata) tows.
    Mean seabird catch rates were estimated for the main fisheries with observed seabird captures: for ling longlines mean catch rates ranged from 0.098 seabirds per 1000 hooks (s.e. = 0.020) in LIN 4 to 0.057 (s.e. = 0.012) in LIN 5; for hoki fisheries, 0.010 seabirds per tow (s.e. = 0.004) at the Chatham Rise to 0.023 (s.e. = 0.017) at the west coast South Island fishery; and for squid fisheries, 0.118 seabirds per tow (s.e. = 0.027) at SQU 6T and 0.163 (s.e. = 0.024) off the Stewart-Snares shelf.
    Total estimates are provided for the main fisheries: 81 seabirds (c.v. = 4%) were estimated caught on chartered tuna longlines in southern waters; 20 seabirds (c.v. = 53%) were estimated from domestic tuna effort in southern waters; 1450 seabirds (c.v = 16%) were caught in ling autoline fisheries by area compared with 685 seabirds (c.v. = 13%) for the four observed vessels by area and season; 334 seabirds (c.v. = 33%) for hoki fisheries; and 710 seabirds (c.v. = 11%) for squid trawl fisheries at 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: 87 seabirds from the domestic tuna fishery in northern waters; 43 seabirds from trawls targeting species other than hoki and squid.
    Of the reported captures, 690 were returned for identification and represented nine albatross and eleven petrel taxa, one of which was previously unrecorded as caught during observed fishing operations: broad-billed prion (Pachyptila vittata). About 86% of the seabirds returned for identification comprised three taxa: 52% were white-chinned petrels (Procellaria aequinoctialis), 20% were white-capped albatrosses (Thalassarche steadi), and 15% were sooty shearwaters (Puffinus griseus).