Migrations and hydrography determine the abundance fluctuations of blue whiting (Micromesistius poutassou) in the Barents Sea

The Barents Sea is the north-eastern fringe of the distribution of blue whiting (Micromesistius poutassou). Fluctuations in distribution and abundance of blue whiting in the area have been marked. Two hypotheses are put forward to explain these fluctuations. First, rich year classes in the main Atlantic stock of blue whiting may contribute to increased abundance in the Barents Sea. Second, variations in hydrography, such as influx of warm Atlantic water, may be particularly important in this fringe area. We investigated these hypotheses using data from bottom trawl surveys conducted during the period 1981-2006. Variations in abundance (measured either as incidence or density) and distribution were correlated with recruitment in the Atlantic stock of blue whiting as well as hydrographic conditions. Regression analyses indicated that the abundance fluctuations are primarily determined by variations in recruitment of Atlantic blue whiting, a strong year class leading to high abundance in the Barents Sea the year after spawning. However, salinity anomaly in the Fugløya-Bear Island transect during the previous year, an indicator of high inflow of Atlantic water, had also a significant, positive effect. Thus, the data suggested a climatic modulation of dynamics that were primarily determined by recruitment of blue whiting in the main Atlantic stock. Analyses of size structure as well as earlier studies on population genetics supported this conclusion