Predation by Atlantic cod Gadus morhua on northern shrimp Pandalus borealis in inshore and offshore areas of Iceland

Abstract

Northern shrimp Pandalus borealis is found in both inshore and offshore areas around Iceland, where it has supported an important commercial fishery. However, in the past 15 yr the northern shrimp population has decreased in size and collapsed in most of the inshore areas. In this study, the importance of Atlantic cod Gadus morhua on northern shrimp stock dynamics was studied by comparing stomach contents of cod between 2 different habitats, inshore and offshore northern shrimp fishery areas. Many prey items were observed in cod stomachs, but only a few dominated. The most important prey types, in decreasing order of importance, included northern shrimp, fish and euphausiids in the inshore area, as opposed to capelin Mallotus villosus, other fish species, northern ambereye Hymenodora glacialis and northern shrimp in the offshore area. Low northern shrimp biomass was observed during periods of high cod density, suggesting that predation by cod affected northern shrimp biomass in both areas.