Estudos biológicos-pesqueiros do espadarte (Xiphias gladius, Linnaeus, 1758) capturado pela frota de espinhel-de-superfície sediada em Itajaí (SC) no Atlântico sudoeste

Abstract

Since the 50’s, Xiphias gladius (Linnaeus, 1758) has been captured along the Brazilian coast by surface longliners. This is the second most important target species for the tuna fleet based in Itajaí, Santa Catarina State, after the blue-shark, Prionace glauca (Linnaeus, 1758). The study was based on data from sea observers, log books and carcass ladings of Xiphias gladius, Linnaeus, 1758) from the pelagic longline fleet based in Itajaí, which operated in the southwest Atlantic. Covariance models were fit to the catches (weight, kg) of swordfish and the effects used were: (1) the years 1997, 1998, 2001, 2002 e 2007 (2) lunar phases and (3) seasons. The covariate was fishing effort (hooks). The highest moon catches occurred on the first quarter moon and during wintertime. The Mantel-Haenszel procedure was used to test the hook selectivity and showed that the type “J” hook (J 9/0 10º offset), traditionally used by the fleet, have 1.2 more chances of catching Xiphias gladius than the “circle” hook (18/0 10º offset), used as an optinal device to reduce sea turtle bycatch. The M-H test showed that the J hook has 1,2 more chances of catching Xiphias gladius than the circle hook. The conversion of individual carcass weights (kg) to total length (cm) for the years 2000 to 2002 showed that 66% of the catches were sub-adults.