Size, locality and seasonally related feeding preferences of common wolffish (Anarhichas lupus L.) from north-Norwegian waters

Abstract

The gut contents of 1000 common wolffish (Anarhichas lupus L.) from north-Norwegian coastal areas and two open sea localities in the Barents Sea, sampled between March 1989 and September 1993, were quantified and categorized. The material from the two areas with seasonally most abundant fish samples (west-Finnmark and Troms) were further analysed. More than 96 different prey species were found in the wolffish gut content, 31 of which had a frequency of occurrence higher than 2%, and only 12 species had a relative biomass importance higher than 2%. In terms of total weight, the most important prey categories were, in decreasing order: sea urchins, bivalves, crustaceans and gastropods. The diet varied with time and area, and was more pronounced with size of the fish. At the west-Finnmark stations, wolffish ate relatively more echinoderms, whereas at the Troms stations relatively more gastropods and bivalves were found in the guts. Medium-sized individuals mainly fed on echinoderms, crustaceans and gastropods, while larger individuals consumed more bivalves and fish. The apparent size-dependent diet suggests the presence of an ontogenetic niche shift in wolffish associated with a body length of about 75 cm.