By-catch reduction in the brown shrimp, Crangon crangon, fisheries using a rigid separation Nordmore grid (grate)

A series of experiments was conducted with a rigid separation grid in an attempt to reduce the levels of by-catch and subsequent discarding of juvenile fish of commercial importance in the brown shrimp Crangon crangon, fisheries of the English East coast. Three designs of grid were tested including two constructed from stainless steel and one from plastic. The effectiveness of the grids was assessed by comparing the catches from the twin beam trawls used in this fishery. One beam trawl was fitted with the grid the other kept as standard. The by-catch levels of plaice, Pleuronectes plattessa, and whiting, Merlangius merlangus were reduced significantly, with no significant loss of shrimp, C. crangon. The selectivity of the grids were determined by two methods, first by comparing the numbers at length retained in each trawl and, second by the fitting of a small mesh retention cover over the escape hole of the grid. Selectivity parameters Were obtained for both species. The selectivity, of two further bar spacing was assessed for the final design of grid. The biological consequences of introducing the grids into the shrimp fleet of the European Union are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.