Prey partitioning between cod (Gadus morhua) and minke whale (Balaenoptera acutorostrata) in the Barents Sea

Abstract

Stomach samples of minke whale (Balaenoptera acutorostrata) and cod (Gadus morhua) were collected on the northeastern parts of the Finnmark coast, northern Norway, in 1998 and 1999 to investigate prey preference, niche overlap and niche width for the two species. A survey to estimate prey abundance was also conducted. Prey preference, niche overlap and niche width were described using Manly's alpha (α), Pianka's index (Ojk) and Levin's index (B), respectively. The diet of cod consisted mainly of capelin, deep-water shrimp, gadoids and krill. The smallest cod (≤64 cm length) preferred capelin, whereas the largest cod (>64 cm length) preferred gadoid species, including cod. The minke whale diet consisted mainly of capelin (Mallotus villosus), herring (Clupea harengus) and krill, and showed a particular preference for herring and capelin. Krill were consumed in large quantities, but did not seem to be a preferred food item for either cod or minke whales. In contrast to cod, which fed very little on herring, the minke whale fed heavily on herring in some areas. The niche widths for both cod and minke whales were relatively low, and the diet overlap between minke whale and cod was low.