Effects of fishing strategy on relative selectivity in trawls, longline and gillnets
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Exploitation of fish stocks is dependent on effort, catchability, the selectivity of the gear used, and the fishermen's choice of time and place. A full-scale fishing experiment was conducted in February 1996 at the coast of Finnmark, Norway; involving a trawler, a longliner and a gillnetter. The objective was to investigate how the length distributions of the catches were influenced by the gear type and the fishermen's strategy in fishing operations. The target species was North-East Arctic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). The study analyses relative selectivity of the gears during a week when the boats fished in a predestined area, and during a week when the skippers were allowed to fish as close to commercial operation as possible with regard to choice of fishing grounds and depths. Gillnet catches consisted almost solely of large cod. Trawl and longline fished similar length distributions of cod although the L50 for cod was higher in long line than in trawl. The fishing strategy of the longliner increased the mean length of haddock in the second part of the experiment. Other length and species distributions were almost unaffected.