Cod (Gadus morhua L.) off Møre - Composition and migration. In: The propagation of cod Gadus morhua L.: an international symposium, Arendal, 14 - 17 June 1983
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Important spawning- as well as nursery- and feeding areas for cod, Gadus morhua L. are found off the Møre coast. In this paper age compositions, age at first spawninq, otolith patterns and migration of cod in the Møre area are studied. The results are used to describe the dynamic of a local cod population. The relationship between coastal cod and north-east Arctic cod is discussed. Immature coastal cod tagged off the Møre coast were mainly stationary before maturation. When mature, cod from various localities tended to migrate partly to the main spawning ground off Sunnmøre, and partly to local spawning areas. A limited number passed the Møre coast to the southern Norway coast and the North Sea. The otolith pattern and age at first spawning seemed to be relatively consistent for cod from various localities off the More coast. However, during the spawning season the influence of older cod with a more complex otolith pattern and higher age at first spawning gradually increased. The parameters gradually change from those characteristic of the Møre coastal cod to those of the north-east Arctic cod which dominated the catches during the time of most intense spawning. However, the original coastal cod was still present and spawning on the same grounds. The spawning population off Sunnmore was made up of cod from various feeding areas, both off and north of Møre, which to a great extent returned for repeated spawning. Further cod in the various feeding areas off Møre were composed of groups of fish with different migratory tendencies, including those spawning in or close to the nursery area and long distance migrants. The difficulties of using otoliths as an stock discriminating parameter are discussed.