Ecological adaption of reproduction in Arctic cod

Abstract

A recent period (1977-1982) of cold climate in the Barents Sea resulted in a greatly reduced feeding area available for the Arctic cod and in consistent low recruitment. With the start of a warmer period in 1982/83 the area and potential for production of cod biomass expands and recruitment has increased. An hypothesis is presented that through evolutionary processes the reproduction of the Arctic cod is adjusted to the variations in the feeding area caused by climatic fluctuations. Historical data on sea temperature and ice cover are used to describe the climatic fluctuations for the period 1900-1983 and these are compared with data on fluctuations in yearclass strength. It is concluded that conditions favouring high survival rates of cod larvae must be related to the occurrence of high temperatures in the Atlantic component of the Norwegian current. The processes and/or phenomena must have a large time- and space scale. This is also confirmed by the high incidence of tempora1 similarity in survival success of the stocks of cod, haddock and herring in this area.