Seabird by-catch in the Patagonian toothfish longline fishery at the Prince Edward Islands: 1999–2000

This paper summarises seabird bycatch during the fourth year (July 1999-June 2000) of sanctioned longline fishing for Patagonian toothfish Dissostichus eleginoides in the Exclusive Economic Zone around South Africa's Prince Edward Islands. Data were obtained from fishery observers aboard all 11 sanctioned fishing trips. Fishing effort was 7.4 million hooks, a 45% increase on the number of hooks set in 1998199. Observers reported 268 birds of six species killed. White-chinned Petrels Procellaria aequinoctialis predominated (92.2%), followed by Eastern Yellow-nosed Mollymawks Thalassarche [chlororhynchos] bassi (3.5%), Grey Pretrels P. cinerea (l.8%), Grey-headed Mollymawks Thalassarche chrysostoma (1.5%) and giant petrels Macronectes spp. (1.1%). Average seabird bycatch rate by sanctioned vessels was 0.036 birds per 1 000 hooks, more than double that reported in 1998/99, but still considerably less than that reported in either 1996/97 or 1997/98. The absolute number of birds killed increased more than threefold compared to 1998/99 due to the marked increase in fishing effort.
Variance in bird bycatch rates among trips ranged from 0.000 to 0.142 birds killed per 1 000 hooks. Birds were killed on 7.7% of sets, with most (68%) birds killed on only 49 sets that had multiple casualties (2.8% of sets). As in previous years, much of the variance could be explained in terms of fishing season (higher bycatch rate in summer), time of setting (higher during the day), and distance from the Prince Edward Islands (higher within 200 km of the islands).