The Utility of Square Mesh Codends As a Management Measure in the Portuguese Nephrops Trawl Fishery

The new discard ban/landing obligation in European waters will result in a renewed interest in selectivity studies. However, the usefulness and justification of developing gear selectivity for management purposes depends on the survival and full recovery of individuals escaping from codends or other trawl areas.

Although a direct link between gear selectivity and survival cannot be assumed, higher survival rates were observed for individuals escaping from selective devices that promote escape behaviour and reduce stress and injury during the escape process, thus justifying the adoption of gear-based management measures in a number of fisheries.

 Using selectivity data for Norway lobster (Nephrops norvegicus) in standard codends 70mm mesh size and modified square mesh ones, as well as comparative estimates for survival of escapees from these two types of codends, we propose to simulate their combined effect on fishing mortality, and its short and long-term impact on population biomass and catch. The objective of this study is to provide support for an informed decision on the introduction of gear alterations in management plans for Norway lobster fishery.

Key-words: Selectivity; Unaccounted mortality; Trawl fishing; Norway lobster; Portuguese coast