Reduction of elasmobranch by-catch in the hake semipelagicnear-bottom longline fishery in the Algarve (Southern Portugal)

Abstract

: Elasmobranch fish, particularly deep-sea sharks, are the mostimportant component of the by-catch of the hake semipelagic near-bottom ‘pedra-e-bola’ longlinefishery in the Algarve (South Portugal) and most of these fish arediscarded. The effects of the removal of the lower hooks were evaluated,in terms of target and by-catch reductions, by quantifying the catchesof each hook relative to the distance from the bottom. The analysisshowed that most European hake (Merluccius merluccius), thetarget species of this fishery, were caught in the middle rangeof the hooks, with very few individuals caught near the bottom,whereas for sharks the situation was the opposite, with most hookednear the bottom. The removal of the lower three pairs of hooks wouldresult in a small reduction in the catch of the target species,but a much more significant reduction in elasmobranch by-catch.In the specific case of the blackmouth catshark (Galeus melastomus),discard mortality would be further minimized due to the fact thatthe lower hooks capture significantly smaller animals that are alwaysdiscarded compared with hooks that are more distant from the bottom.