Studies of minke whale (Balaenoptera acutorostrata) ecology in the northeast Atlantic: Description of the 1993 scientific catch operations and preliminary results from stomach analyses and resource surveys

Abstract

Ecological studies of the Northeast Atlantic minke whale (Balaenoptera acutorostrata), initiated in 1992, were continued in 1993. The field work was carried out in spring (15 April-15 May), summer (15 June-12 July) and autumn (25 August-20 September) using four chartered small-type whaling vessels which operated in four selected subareas. To ensure random sampling of whales, stringent sampling procedures, where the vessels searched for whales along predetermined transects within each subarea, was applied. Concurrent with the sampling of minke whales, estimates of potential prey abundance were carried out using accoustics and trawls. A total of 69 whales were shot; 5, 35 and 29 in spring, summer and autumn, respectively. Preliminary results from the stomach analyses indicate a diet where fish play a very prominent role. Diet varied between both periods and areas. Gadoid fish species dominated the spring diet. In summer and autumn the diet in the northmost areas (Spitsbergen and Bear Island) was primarily characterized by the presence of krill, to a much lesser extent by capelin. This is consistent with an increase in krill and severe decrease in capelin availability in these areas in 1993. In the coastal areas of North Norway, herring is the dominant planktivorous fish, and was also the most important food item for the whales both in summer and autumn. To some extent, however, the herring was accompanied by some gadoid species during summer. Whale consumption of 0-group fish were observed to be rather limited. Along with material necessary for the study of condition and diet, sampling was also carried out for a number of other studies included in the framework of the Norwegian scientific catch program.