Catch rates of swordfish and of blue shark in the Southwest Atlantic from 1980 to 2000 decades

Abstract

Swordfish (Xiphias gladius) is one of the main targets of the national and of part of the leased Brazilian pelagic longline fleet. However, the catches of blue shark (Prionace glauca) are also high. In order to get more knowledge about the duality of catches of swordfish and blue shark, catch data from the Brazilian national and leased fleets from 1980 to 2009 were analyzed. In some of the fishing grounds, catch rates of both species are high, but in other areas, only one species is abundantly caught. Leased boats from Japan and China Taipei never aimed at any of those two species, hence the catches were always small. However, the leased fleet from Spain clearly focuses its actions in areas where catch rates of swordfish are high. The national fleet focuses effort both in areas where swordfish dominates and in areas where catch rates of swordfish and blue shark are concomitantly high. If the intention is to diminish the impact of fishing effort on the population of blue shark, an alternative would be to enforce the fishing fleet to operate only in areas where catch rates of swordfish are high and where catch rates of blue shark are low.