Evaluation of the sieve net as a selectivity-improving device in the Belgian brown shrimp (Crangon crangon) fishery

Abstract

Abstract The fishery for brown shrimp ( Crangon crangon ) in the North Sea is carried out by more than 600 vessels, with total annual brown shrimp landings of around 20,000 t. Due to the small mesh size used, the catches also contain large amounts of unwanted by-catch. To find ways of reducing this by-catch, experiments were carried out during a one-year period with a sieve net rigged in a brown shrimp beam trawl. It was tested for its selective properties and an evaluation was made of its operational characteristics. The loss of commercial shrimp catch when using a sieve net was 15% or less in favourable conditions. Certain components of the catch can, however, lead to a distortion of the outlet with a reduction of the commercial catch of over 30%. It is likely that technical alterations to the outlet can prevent this. The sieve net showed very poor selective properties for commercial fish species with a length below 10 cm. Above 10 cm the selection improved with increasing length. Especially for Age 1 and older fish, this selective device serves its purpose. A significant reduction of non-commercial fish and invertebrates was also observed.