Tables and diagrams on trophology of walleye pollock in the western Bering Sea

Abstract

State of zooplankton, as the food base of walleye pollock, in the western Bering Sea in the early 21^st century is considered. Warm period of the 2001-2006 changed to cold period of the 2007-2013 and, after the transitional year of 2014, a new warm period began in 2015 that could be seen on a number of parameters including the ice cover that was the lowest for the last 15 years. In the previous warm period, the walleye pollock food base wasn’t reduced in this area, in contrast to the eastern Bering Sea where the biomass of its favorite prey was lowered. The same is observed in the beginning of the new warm period. Data on zooplankton abundance are presented, including both dominant and minor groups, that allows to assess a real feeding conditions for six size classes of walleye pollock. Food supply of pollock is evaluated quantitatively as a number of its monthly rations in the zooplankton stock, taking into account age and regional properties of its diet. This index was high in the western Bering Sea for both warm and cold periods, any deficit of food for pollock was never observed there.