Feeding habits of demersal fish in Icelandic waters: a multivariate approach

Stomach data were examined to assess the key factors that determine diet composition in some of the most important demersal fish species in Icelandic waters and to identify major feeding guilds. The data were collected during the groundfish surveys conducted by the Ma- rine Research Institute in 1992. The factors examined included geographic position, depth, season, and fish size. Data were analysed using multivariate methods: canonical correspon- dence analysis (CCA), non-metric multi-dimensional scaling (NMDS), and hierarchical clustering. For the CCA, important explanatory variables for the observed feeding patterns were found using forward stepwise selection. Fish size was the most important explanatory variable for most species, reflecting distinct ontogenetic shifts in diets. A large variation in diet composition was observed, and the CCA model explained 6e16% of the total variation. The spatial and seasonal variability in diets reflected, in general, patterns of prey availabil- ity. Among the main predators, the two major feeding guilds were (i) species preying mainly on echinoderms, supplemented with fish and other benthic invertebrates, and (ii) species preying mainly on crustaceans and fish.