The effect of forced mesh opening in the upper panel of a Nephrops trawl on size selection of Nephrops, haddock and whiting

In an attempt to reduce catches of juvenile fish in the Icelandic Nephrops norvegicus fisheries, the mesh sizes in the upper part of a commercial Nephrops trawl were increased and the netting hung to force wide mesh opening.Two different designs, each with 135 mm nominal mesh upper panel were compared to an unmodified commercial trawl in June 2009. Design A had a 23.2 m long panel and design B had a 16.1 m long panel, extending respectively to 9.7 and 15.0 m from the cod-line. The panels in both designs were one third narrower and longer than the matching lower panel.With design A, about half of Nephrops, haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus) catches were lost, while with design B, the losses were restricted to smaller specimen of fish and Nephrops, i.e. a marked size selection was observed.These trials demonstrate the potential for size selection by a simple manipulation of a Nephrops trawl to reduce discarding.