Variation of peak spawning of arcto-Norwegian cod (Gadus morhua L.) during the time period 1929-1982 based on indices estimated from fishery statistics. In: The propagation of cod Gadus morhua L.: an international symposium, Arendal, 14 - 17 June 1983
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The weekly amounts of roe and cod landed in the main spawning area at Vestfjorden are known since 1929. An index of the median of the spawning intensity curve was constructed on the basis of an analogy to the gonosomatic index using the weight ratio roe/cod. The index of median reveals a delay of about one week during the time period from 1929 to 1982. This method is compared to the median of spawning curves based on net hauls of newly spawned eggs from the traditional spawning grounds for the time period 1976 to 1982. Sources of errors in the fishery statistics are discussed.