Schooling behaviour of arctic cod, Boreogadus saida, in relation to drifting pack ice

Concentrations of arctic cod were detected with a hydroacoustic system in Resolute Bay, NWT during 2 weeks in August of 1986. Fish biomass within the bay was about 30 t. The fish were feeding primarily on amphipods, which were abundant. When the daily location of the schools was examined in relation to the extent and position of drifting pack ice, a pattern emerged suggesting that the distribution of the fish was influenced by the amount and location of ice cover. If the bay was relatively ice-free, the density of schooling cod was high and the size of the schools, as 2-dimensional surface area, was generally small. When ice covered the bay, density within the schools was lower and they occupied more area. Arctic cod were most dispersed after the bay had been filled with pack ice for several days. It is postulated that this behaviour is a response to potential predation by seabirds and marine mammals.