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

Elasmobranch fish, particularly deep-sea sharks, are the most important component of the by-catch of the hake semipelagic near-bottom 'pedra-e-bola' longline fishery in the Algarve (South Portugal) and most of these fish are discarded. The effects of the removal of the lower hooks were evaluated, in terms of target and by-catch reductions, by quantifying the catches of each hook relative to the distance from the bottom. The analysis showed that most European hake (Merluccius merluccius), the target species of this fishery, were caught in the middle range of the hooks, with very few individuals caught near the bottom, whereas for sharks the situation was the opposite, with most hooked near the bottom. The removal of the lower three pairs of hooks would result 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 that the lower hooks capture significantly smaller animals that are always discarded compared with hooks that are more distant from the bottom.