Growth of North-east Arctic cod (Gadus morhuaL.) in relation to ambient temperature

Michalsen, K., Ottersen, G., and Nakken, O. 1998. Growth of North-east Arctic cod (Gadus morhua L.) in relation to ambient temperature. - ICES Journal of Marine Science, 55: 863-877. Temperature related changes in horizontal distribution of North-east Arctic cod are described and the influence of temperature on the growth is interpreted. By using data from acoustic and bottom trawl surveys in the Barents Sea conducted in February 1988-1995, mean length at age is related to the winter temperature. Mean lengths at age increased with increasing temperature for cod of age 2-6. Mean individual growth was highest for year classes experiencing high temperatures. Due to the seasonal migration patterns of cod, the actual annual means of ambient temperature as well as the diVerences between these means are lower than the values from February alone, used in this study. Thus, by using the ambient winter temperature instead of annual mean values the eVect temperature has on growth is probably underestimated. Increased abundance of young cod is associated with an extension of the distribution area towards east and north into colder water. Even though the individual consump- tion of capelin by cod increased in these years, the increase in abundance was accompanied by reduced growth. Hence a growth-temperature relation may wrongly be interpreted as a growth-density (abundance) dependency if ambient temperature is not included in the analysis. ? 1998 International Council for the Exploration of the Sea