The relation between the spatial distribution of early juvenile cod (Gadus morhua L.) and zooplankton biomass in the Barents Sea

Abstract

The year class strength of Arcto-Norwegian cod (Gadus morhua L.) in the Barents Sea is extremely variable. One of the key indicators for a possible strong year class is water temperature since good year classes may be produced in warm years while they seldom if ever occur in cold years. Water temperature alone is not sufficient to produce a good year class. Thus it is conjectured that when there is a strong flow of Atlantic water from the Norwegian Sea into the Barents Sea it not only warms the water but transports large quantities of zooplankton and hence provides better survival conditions for cod. Survey data from the Barents Sea for the years 1977 through 1984 are examined to determine the relation between zooplankton abundance and the spatial distribution of juvenile cod and to investigate if zooplankton abundance is associated with the flow of Atlantic water. For all years, more zooplankton on average were found in areas with cod than in those without cod. Total zooplankton abundance increased significantly in the Barents Sea concurrently with an increased inflow of Atlantic waters in 1981.