Interactions between Atlantic cod (Gadus morhua) and its prey species in the Barents Sea

The Barents Sea ecosystem has experienced large changes in the 1980s and 1990s. The Barents Sea capelin (Mallotus villosus) stock, which is the main forage fish in the area, was seriously depleted in 1986-1988 and again in 1993-1995, and the abundance of several other important fish stocks has also been very variable. These variations have to a large extent been caused by multispecies interactions. Before 1990, such interactions were not taken into account in the fisheries management in this area, causing severe problems in the management. The Atlantic cod (Gadus morhua) is the most important predator in the Barents Sea ecosystem. The consumption by cod of various prey species in the period 1984-1995 was calculated. The abundance estimates of some of the most important prey species are compared to the calculated consumption by cod, and the influence of cod on the fluctuations in prey abundance is discussed. The growth rate and weight at age of cod varied greatly throughout the period, and the relationship between this variation and variation in cod consumption is discussed. How multispecies interactions are taken into account in today's assessment and management is also described.