Economic impacts of changes in the population dynamics of fish on the fisheries of the Barents Sea

A bioeconomic simulation model of the two interacting fish species cod (Gadus morhua) and capelin (Mallotus villosus) and their fisheries is presented and applied to assess the consequences of changes in the population dynamics of these important fish stocks in the Barents Sea. In each scenario, the population dynamics of the fish species are changed by an external reduction of the reproductive rates and/or the carrying capacities. The stock sizes and landings of fish are calculated for each fishing period and the net present values of profits from fishing are determined for time periods prior to and after the change in population dynamics. Results show that reduced growth rates or carrying capacities both lead to lower stock levels and consequently to smaller catch sizes. There is only a small short-term economic impact on the fisheries but the long-term consequences are quite pronounced. In some cases, a higher fishing activity in the first few years after the change in population dynamics causes harvest sizes to remain stable despite diminishing stock sizes. This stabilizes the returns from fishing in the short run but veils the apparent negative long-term impact on the fisheries resulting from adversely affected stock dynamics.