Ambient temperature and distribution of northeast arctic cod

Abstract

Most studies on the effects of field temperature on fish distribution and population parameters have considered the temperature and its variability at fixed stations or sections rather than the temperature in the actual surroundings of the fish, the ambient temperature. From spatial distribution of fish density and temperature, estimates of ambient winter temperature were established for 1-7 year old Northeast arctic cod in the period 1988-1995. Four different estimates were calculated for each age and year based on fish density observations from acoustic- and bottom trawl surveys and temperature recordings in two depth layers, bottom as well as 100m depth-bottom. The estimates of ambient temperature were compared and also examined in relation to temperature series in fixed areas and a standard section, the Kola meridian. As expected the interannual variability in ambient winter temperature was found to be larges than in the Kola-section series. The ambient temperatures were found to increase with age. For the younger age groups the ambient temperature seemed to decrease with increasing numbers of fish. The mean ambient temperatures are also compared with the temperatures used for calculations of growth and consumption rate in cod in the ICES Working groups.