Abstract

Coastal and pelagic fishing activities in the area of Necochea harbour, where high mortality of franciscanas (Pontoporia blainvillei) in gillnets had been previously reported, and at Claromeco, a small gillnet fishing camp, were monitored in 1988-90 and 1989-90 respectively. Necochea has three main types of fishing operations: gillnetting (target species: sharks), purse-seining (target species: anchovy and mackerel) and trawling. In Claromeco, only gillnets are used. Gillnet and purse-seine operations cause dolphin mortality. Gillnet fishing effort has increased in Necochea since 1984. In Claromeco, the fishing effort also seems to be increasing. The estimated number of cetaceans killed by gillnets at both localities varied between 50.9 to 68 individuals per year (lower 95% CI 32.7-45.1; upper 95% CI 67.5-125.1). The main species affected are franciscanas (76.5%), Burmeister’s porpoises, Phocoena spinipinnis (18.7%), dusky dolphins, Lagenorhynchus obscurus (2.2%) and common dolphins, Delphinus delphis (2.6%). Although the gillnet fishing effort in Claromeco is smaller, 75.4% of the 1989 and 94.9% of the 1990 estimated franciscana captures were in this locality. This may be because in Claromeco gillnets are set at lower depths and shorter distances from the coast, where franciscanas appear to be more common. Thus fishing from several similar small fishing camps, located all along the coast of Buenos Aires Province, might be more dangerous to the franciscana population than vessels from larger harbours. Mortality of dusky and common dolphins in the purse-seine fishery was also observed. The kill due to this fishery in the Necochea area is estimated at 68-102 individuals in 1989 and 5 in 1990.