Diet overlap between North-East Arctic cod and haddock in the southern part of the Barents Sea in 1984-1986

The diet composition of North-East Arctic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) are examined from stomach content data. Fish were collected in the southern part of the Barents Sea from 1984 to 1986. A total of 4790 cods and 1361 haddocks were divided according to season (winter, spring and fall) and fish size in 10 cm size classes. Only fish bigger than 10 cm length were considered. Diet overlap between the two species for each size group in each season was calculated using the Schoener's index. North-East Arctic cod show a size dependent shift in the diet. Fish smaller than 20 cm prey mainly on crustaceans (euphauiids, deep sea shrimp and amphipods). Above 20 cm, cod incorporate fish in the diet to a larger degree, the degree increasing with the size of the predator. Some seasonal changes are described. Haddock, a less ichthiophagous, bivalves and polychaetes. In general the diet overlap is low except in spring and fall when the smaller size groups of both species prey on euphausiids. The results are compared with previous information on cod-haddock interaction