THE IMPACT OF THE HAKE MERLUCCIUS SPP LONGLINE FISHERY OFF SOUTH-AFRICA ON PROCELLARIIFORM SEABIRDS

In 1994, an experimental longline fishery for hake Merluccius spp. com menced in the shelf waters off South Africa. Participants were require d to record any birds caught, and these data were supplemented by ship -based observers on several vessels. Longlines are set at night, and t he white-chinned petrel Procellaria aequinoctialis was the only seabir d species caught while attempting to scavenge bait during gear setting . Small numbers of great shearwaters Puffinus gravis and pintado petre ls Daption capense were killed during hauling operations. The hake lon gline fishery is estimated to kill 8000+/-6400 white-chinned petrels a year in South African waters at a rate of 0.44 birds per 1000 hooks. This represents <1% of the global whire-chinned petrel population, but is cause for concern given (1) the slow reproductive rate among proce llariiform seabirds; (2) the projected growth in the longline hake fis hery; and (3) the increasing numbers of white-chinned petrels being ki lled in other longline fisheries. Light intensity was the most importa nt factor for explaining variation in the number of petrels caught dur ing setting; when line shooting was completed prior to the ina ease in white-chinned petrel activity (c. 2.5h before sunrise), few birds wer e caught. Measures to reduce excessive seabird by catch include: (1) t he introduction of bird lines on all vessels; (2) restricting the sett ing of lines to times of least bird activity; (3) minimum use of deck lighting during setting; and (4) ensuring that baited hook sink as fas t as possible when deployed Hauling mortalities can be reduced by dive rting offal outlets to the opposite side of the vessel to where the lo ngline is being hauled. (C) 1997 Published by Elsevier Science Ltd.