Diet and food availability for northeast Atlantic minke whales Balaenoptera acutorostrata

Ecological studies of the Northeast Atlantic minke whale (Balaenoptera acutorostra) were\ncarried out during spring (mainly April-May), summer (June-July) and autumn (AugustSeptember)\nin 1993 and 1994. Four small-type whaling vessels were chartered for operations\nin four selected subareas in Norwegian and adjacent waters. To ensure random sampling of\nwhales, stringent sampling procedures, where the vessels searched for whales along\npredetermined transects within each subarea, were applied. Estimates of potential prey\nabundance were obtained from a review of results from synoptic surveys and from long-term\nsurvey series. Samples were obtained from 63 and 70 whales in 1993 and 1994, respectively.\nResults from forestomach analyses indicate a minke whale diet where fish play a very\nprominent role during most of the season. Diets varied between both periods and areas.\nGadoid fish species dominated the spring diet. In summer and autumn the diet in the\nnorthmost areas (Spitsbergen and Bear Island) was primarily characterized by krill\nThysanoessa spp., to a much lesser extent by capelin Mallotus villosus. This is consistent with\nan increase in krill and severe decrease in capelin availability in these areas in 1993 and 1994\ncompared with previous years. In the coastal areas of North Norway, herring Clupea\nharengus is the dominant planktivorous fish, and was also the most important food item for\nthe whales both in summer and autumn. To some extent, however, the herring was\naccompanied by some gadoid species during summer. Whale consumption of 0-group fish was\nrather limited. Statistical analyses of potential prey preferences indicate a preference for\nherring and capelin. Given the opportunity to choose, it appears that minke whales will\ngenerally favour these two prey species before other actual species such as krill and gadoid\nfish species.