RELEVANCE OF COD (GADUS-MORHUA L.) PREDATION FOR INTER-COHORT VARIABILITY IN MORTALITY OF JUVENILE NORWEGIAN SPRING-SPAWNING HERRING (CLUPEA-HARENGUS L.)

Mortality of juvenile Norwegian spring-spanning herring growing up in the Barents Sea is characterized by a high inter-cohort variability. V ariable predation pressure from the north-east Arctic cod stock has be en proposed as an explanation, but it has been difficult to test this hypothesis with actual field data. Data on the abundance of the main f ish stocks in the Barents Sea ecosystem. collected by the Institute of Marine Research in Bergen during the period 1983-1993, were analysed to test this hypothesis. Since capelin has been the major prey of cod during the period investigated, the relationship between herring juven ile mortality and the abundance of cod, capelin and herring was invest igated,More than 90% of the inter-cohort variation in mortality of juv enile herring observed during this period was explained by a simple mo del using the ratio of capelin abundance to the abundance of juvenile cod as the explanatory variable, The relationship is strong enough to warrant using the simple model for improving the short-term forecasts of recruitment to the spawning stock of Norwegian spring-spawning herr ing. (C) 1998 International Council for the Exploration of the Sea.