Do harp seals Phoca groenlandica exhibit particular prey preferences?

Abstract

Feeding ecology studies of harp seals Phoca groenlandica were carried out in the south-eastern Barents Sea in February 1993, and in the north-eastern Barents Sea in October 1995. Stomach/intestine contents were obtained from 76 and 18 harp seals in 1993 and 1995, respectively. In both years, acoustic surveys aimed to estimate the abundance of potential prey items were conducted concurrently with sealing activities. The abundance of prey differed substantially between the areas. To the west of the southernmost area (CKK), herring Clupea harengus was by far the most abundant prey item, while polar cod Boreogadus saida predominated to the east (Pechora). In the northern area crustaceans, Thysanoessa sp. and Parathemisto libellula, were by far the most abundant prey items. The composition of seal diets varied between areas. In the south-eastern Barents Sea, herring and polar cod dominated the diet in the western and eastern subarea, respectively, with significant contributions also for cod, Gadus morhua, various other bottom fish, and shrimp. In the CKK area, the role of herring appeared more pronounced in terms of abundance than in terms of seal food. Due to methodological problems, however, any conclusions about preference for this species should be interpreted cautiously. In the Pechora Sea, no evidence was found for particular preferences for the two most commonly eaten prey species polar cod and herring. In the north-eastern Barents Sea, polar cod appeared to be the most important prey accompanied by P. libellula. Statistical analyses revealed no clear preference by the seals for these two prey species, while a very clear negative preference for krill was demonstrated.