Report on technological innovations and management scenario’s to mitigate fishing impacts on the benthic ecosystem and their socio-economic consequences in regional seas

This report provides a detailed account of the field and modelling studies carried out in the BENTHIS project in the Baltic Sea, North Sea, Western Waters, Mediterranean and Black Sea on the mitigation of bottom trawling impacts on the seafloor and benthic ecosystem. The studies were conducted in close collaboration with fishers and gear manufacterers and focused on the major bottom trawl fisheries in European waters: otter trawl fisheries for demersal fish, otter trawl fisheries for Nephrops, beam trawl fisheries for flatfish, beam trawl fisheries for brown shrimps, beam trawl fisheries for whelks, dredge fisheries for bivalves (mussel, scallops). Both technological innovations and alternative management scenarios were explored. Technological innovations The following technological innovations were studied: (i) Lifting otterboards (semi-pelagic otterboards, jumper boards); (ii) Reducing sweep length in Nephrops otter trawls; (iii) Gear modifications (weight, chain, mesh size); (iv) Pulse trawls replacing mechanical stimulation by electrical stimulation; (v) Use of passive gear (creels and pots). Semi-pelagic otterboards New scaled otterboards designed by Italian SMEs (Small and Medium Size Enterprises) were preliminary tested in a wind tunnel and in a flume tank and finally tested in full-scale at sea. Sea trials showed a reduction in fuel cost and bottom contact, while the catch efficiency was not significantly affected. Jumper otterboards, tested in the French Nephrops fishery, produced considerably lower level of sediment re-suspensioncompared to the conventional otterboards, while catch rates were not statistically different. Reduced sweep length Sea trials with reduced sweep length in the Nephrops fishery in the Kattegat (western Baltic) indicated that it is possible to maintain similar catch rate of Nephrops, flatfish (plaice, sole) and codfish (cod, haddock) with shorter sweeps. Gear modifications (gear weight, application of chains, mesh size). Sea trials c