Responses in spatial distribution of Barents Sea capelin to changes in stock size, ocean temperature and ice cover

Using data for the period 1972-2010, we relate the variations in the Barents Sea capelin distribution to stock size, ocean temperatures and the area available for dispersal during summer. We find a strong relation between distribution area and stock size, which is most likely caused by a large stock extending the feeding area to meet the higher food demand. However, during the last decade there has been a general expansion of the distribution area and a northward shift of the high-concentration areas, which we relate to the high temperatures and low ice cover observed in the northern Barents Sea during the period. The study shows that ocean temperature and ice cover set the large-scale terms for the capelin distribution, while the stock size determines how capelin uses the available area. Changes of 4 million tonnes in stock size or 1 degrees C in temperature give comparable impacts on the distribution.