Enhancing onboard post-catch vitality of discard Norway lobster (Nephrops norvegicus) for more sustainable Mediterranean trawl fishery

Abstract

The current European Union fisheries policy encourages improving handling practices to increase the survival of discards. Trawling on the Mediterranean upper slope often generates over 30% of discards of the total catch. Among other species, Nephrops norvegicus juveniles are abundantly returned to the sea, sometimes exceeding 40% of discarded biomass. N. norvegicus discard survival probability has been recently shown to be related to vitality on board and to vary seasonally, being especially low during the summer (0.06). Environmental characteristics (especially, high on-deck temperature in summer) make it necessary to improve vitality on board in order to increase discard survival. We therefore tested new discard handling methodologies for a Mediterranean mixed trawl fishery, with N. norvegicus as the target species. The results showed a survival rate on board higher than 0.8 resulting from vitality status improvements achieved by immersing N. norvegicus in cooled seawater on board during the catch selection and discard time. The implementation of this method would make an important contribution to more sustainable Mediterranean trawl fisheries.