DISTRIBUTION, POPULATION-STRUCTURE AND DIET OF SILVERY POUT (GADICULUS-ARGENTEUS-THORI SCHMIDT,J.), POOR COD (TRISOPTERUS-MINUTUS-MINUTUS (L)), 4-BEARDED ROCKLING (RHINONEMUS-CIMBRIUS (L)), AND VAHLS EELPOUT (LYCODES-VAHLII-GRACILIS REINHARDT) IN THE NORWEGIAN DEEP

Populations of some small, demersal roundfish in the Norwegian Deep of the northeastern North Sea were analysed. Data were collected on 3-4 bottom trawl surveys each year in four years. Both silvery pout, four-bearded rockling and Vahl's eelpout were moderately abundant in parts of the Norwegian Deep. The area is deeper than the normal range of distribution of poor-cod and this species only occurred along the edges of the deep-water area. The abundance of silvery pout increased towards the northwest, whereas four-bearded rockling and Vahl's eelpout were more abundant in the Skagerrak. There were some indications of seasonal or ontogenetic migrations. Only 2-3 age groups were present at a time in the silvery pout and four-bearded rockling populations, whereas seven age groups of Vahl's eelpout were recorded. Pelagic or benthopelagic crustaceans formed important parts of the diets of all the four species considered. In addition, poor-cod and four-bearded rockling preyed on polychaetes, whereas Vahl's eelpout ate ophiurids. Interspecific differences in diet composition were found and the similarity of niche characteristics were relatively low.