Growth of capelin in relation to zooplankton biomass in the Barents Sea

Abstract

Growth of capelin in the Barents Sea stock has been found to vary considerably both between years and between different parts of the distribution area. The aim of this paper is to compare such growth variations with measured abundance of zooplankton within the capelin feeding area. In the period 1979-1984 a north-south transect in the Barents Sea was studied one to four times during summer. A negative relationship between the plankton biomass and the density of capelin along the section was evident. During the summer feeding migration the largest capelin, primarily the oldest, but also the largest individuals of each age group, were found in the front of the northward migration. Here they form a capelin front, which can be seen as eating its way through the plankton distribution. Length and weight of capelin were positively correlated with plankton density along the section. From 1987 to 1994, zooplankton abundance has been recorded on several stations taken along the track of an acoustic survey for capelin during September. The mean annual individual growth in weight of capelin was found to be positively correlated with average zooplankton density. The strongest relationships were found between one year old capelin and the smallest zooplankton size fraction, and between three years old capelin and the largest size fraction of plankton. Capelin length, weight and condition factor were also to some degree correlated with plankton density, although significant results were found for only some combinations of capelin age group and zooplankton size fraction.