Atlantic cod (Gadus morhua) diet and the interaction with northern shrimp (Pandalus borealis) in Greenland waters

Abstract

In Greenland waters, Atlantic cod (Gadus morhua) is showing signs of recovery following a collapse in the early 1990s, and quantitative diet studies are needed to address predation on highly commercial species such as northern shrimp (Pandalus borealis). We analyzed 2483 Atlantic cod stomachs from Greenland offshore waters and the correlation between Atlantic cod and northern shrimp abundance. Fish and crustacean prey accounted for 96% of the prey by weight, with the relative importance shifting from crustaceans to fish with increasing cod size. Spatial differences were distinct and northern shrimp dominated the diet in Northwest Greenland (>50% by weight), but declined in importance in Southwest Greenland and was absent from the diet in East Greenland. Instead, other crustacean preys such as krill were important in Southwest Greenland while fish prey was most important in East Greenland. Southwest Greenland was sampled in both summer and autumn, and there was a significant seasonal effect on most prey groups, but most pronounced for Atlantic cod and krill both of which increased in importance. Extensive cannibalism was limited to the largest cod (]70–100 cm]) and mainly in Southwest Greenland. In Southwest Greenland, Atlantic cod and northern shrimp biomass were significantly negatively correlated, while no significant trends were found in Northwest or East Greenland.