Diving observations on Barents Sea capelin at the spawning grounds off northern Norway
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During the spring of 1971 divers made observations at the spawning grounds of the Barents Sea capelin. Large masses of capelin eggs were found at two localities: Loppa, (35-70 m depth) and Nordvågen (12-18 m depth). The eggs were mixed down to a depth of 5 cm with fine gravel (0.5-1.5 cm diameter). Two behaviour patterns of the capelin were observed: Loosely packed schools in the upper layers and dense circulating schools close to the bottom. The latter are believed to be males waiting for ripe females. Egg mortality caused by trawlers was experimentally investigated by dragging trawl bobbins along the egg beds. Eggs stirred up by the bobbins showed higher mortality (up to 10.2% after ten days incubation) than undisturbed eggs and eggs from bobbin tracks (up to 2.5% mortality after ten days incubation). Less than 1% of the eggs on the investigated spawning grounds is believed to be damaged by trawlers. Diverse estimated a 5-10% decrease in the number of eggs on the spawning grounds over a four week period. This was due to a drift of eggs largely caused by wave action and water currents. No predation of the capelin eggs was observed.
SerieFiskeridirektoratets skrifter, Serie Havundersøkelser
vol 16 no 4