Influence of climate on recruitment and migration of fish stocks in the North Sea
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For several decades one of the prime targets within fishery science has been to be able to understand and explain the great variability in the success of survival from egg to mature fish. One of the reasons why such effort has not lead to any clear and quantifiable conclusions, is probably that the direct and indirect influence of the physical climate has so far been underestimated. 22 years of hydrographic data taken during summer over most of the northern and central North Sea, and meteorological data from a station outside western Norway, have been used to derive climatic parameters assumed to be of prime importance for the biological productivity of the North Sea. These time-series together with recruitment and spawning stock size data from the indiuidual ICES working groups, have been used to construct empirical models demonstrating that e.g. more than 70% of the year to year recruitment variability of several of the fish stocks may be explained by the climate/weather prior to and during the time of larval stages. In addition to demonstrate which climatic factors being most important for the biological prosesses, the results of the models indicate that realistic forecasts of recruitment can be given already within the summer of the spawning year. This possibility is of great importance to better manage the fish resources.