System Model (Systmod) for the Norwegian Sea and the Barents Sea

Abstract

The significance of stock interactions and climate change for the ecological balance in the Barents Sea was visualised in the mid-1980’s when an acute deficit of prey species led to mass death among the predators. The crisis occurred after a long period of overfishing the stocks of herring and capelin, and was triggered by a climatic change to favourable recruitment conditions for herring and cod. However, the herring stock was too small to exploit the possibilities, while the cod stock became too large in relation to its food supply. Given the lack of juvenile herring and a reduced capelin stock, the rapidly growing cod stock grazed down all other available prey species in the area, including its own progeny, and starved cod, seabirds and seals appeared on the north Norwegian coast. The capelin fishery collapsed, and the traditional coastal cod fisheries were struck by the most serious crisis on record. The stock evolution in the 1980’s is the background for the development of “Systmod” the system model for the fisheries in the Norwegian and Barents Seas’ (Hamre et al. 1993). The model was developed in co-operation between The Institute of Marine Research (IMR) and Norsk Regnesentral (Norwegian Computing Center). So far it includes herring, capelin and cod.