Beskatningen av skreibestanden - Hva merkeforsøk i Lofoten viser, foreløpig rapport
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Since 1947 annual tagging experiments have been carried out on the cod occurring on the Lofoten Banks during the spawning season. We want inter alia to examine the extent to which the fishermen exploit this stock of fish. The results of previous and of present investigations show that the cod after spawning migrates northwards along the Norwegian coast to the feeding grounds in the Barents Sea. In November and December the shoals again approach the Norwegian coast, where they form the basis of important fisheries during winter and spring. Comparative experiments have shown the hydrostatic tags to be more frequently returned in the long run than several types of buttons and strap tags. The hydrostatic tags have been used in all years; the estimates of how much the fishery takes of the stock, are based on the results obtained by this type of tag. The experiments have been carried out during the main fishing season in Lofoten. The tagged fish will not at once be distributed in a representative manner within the total population occurring on these grounds. The number recaptured on the Lofoten Banks during the season of tagging depends much on when and where the fish is liberated. The material also indicates that the tagging process influences the behaviour of the fish shortly after tagging. The material has, therefore, been dealt with in the following way. The fish recaptured on the Lofoten grounds during the season of tagging is left out of consideration. The number unaccounted for at the end of that season is taken as a basis when calculating the percentage of recovery during the following period. In this way the results from the experiments in a single season should give adequate information as to how much the fishery takes of the stock leaving the Lofoten grounds in that year. The total number of tags returned from the fish leaving the Lofoten banks in the years 1947-51, varies between 13 and 40 %. These results indicate that considerable inroads are made by the fishermen on the stock which has once visited these grounds. Several nations fish upon this stock of cod, e.g. Germany, Great Britain, Norway, and Russia. Most of the tags have heen returned by Norwegian fishermen, especially by those fishing within the Lofoten district. We do not feel sure, however, that all foreign fishermen have returned the tags to the same extent as have our own.
SerieFiskeridirektoratets skrifter, Serie Havundersøkelser
vol 10 no 8