Danish experiments with a grid system tested in the North Sea shrimp fishery

Grids have been proven successful worldwide as bycatch reducers in shrimp f isheries but have never been tested in the North Sea shrimp fishery. The ob jectives of this experiment were to develop and test a flexible grid system for the Danish Fladen Ground shrimp (Pandalus borealis) fishery, which can retain marketable catches of roundfish and Norway lobster (Nephrops norveg icus). The grid system was made of polyamide with a fish escape hole at the top and a Norway lobster escape hole at the bottom. Hinges made the grid f lexible. The grid system was developed acid tested in a flume tank and duri ng sea trials. Two experiments were conducted with a commercial trawler at the Fladen Ground. A standard shrimp codend was compared to a codend with t he grid system simultaneously in a twin trawl rig. There was a relatively l arge and significant reduction in the grid codend of cod (Gadus morhua), ha ddock (Melanogrammus aeglefinus). whiting (Merlangius merlangus), saithe (P ollachius virens), Norway pout (Trisopterus esmarki). Norway lobster, herri ng (Clupea harengus) and witch (Glyptocephalus cynoglossus) but no signific ant difference in weight of shrimp and monkfish (Lophius piscatorius) in th e first experiment. The grid system was altered in experiment 2 resulting i n no significant difference in the catch of cod and saithe above the minimu m landing size while the catch of Norway lobster and shrimp improved signif icantly. Experiments with collecting bags indicated that most fish went thr ough the top fish escape hole. shrimp and Norway pout through the grid or t he bottom Norway lobster hole and Norway lobster mainly through the Norway lobster hole. (C) 2001 Elsevier Science B.V. All rights reserved.