Sharing the Northeast Arctic cod: possible effects of climate change

The Northeast Arctic cod inhabits the exclusive economic zones of Norway and Russia and migrates extensively between these zones. The stock is shared evenly between the two countries, with a small allocation to third countries. Higher temperatures in the Barents Sea and the Norwegian Sea are expected to affect the stock, probably increasing its size and leading to a larger share inhabiting the Russian economic zone. It is also conceivable that some spawning will begin to take place off the coast of Russia in addition to the spawning that now occurs exclusively in Norwegian waters. This paper looks at the implication of this for the division of the stock between the two countries. It is found that a greater presence of the stock in the Russian zone would strengthen rather than weaken the Norwegian bargaining position if the unit cost of fish is not sensitive to the size of the stock. If, on the other hand, the fishing costs are proportional to fishing mortality, Norway’s position would be weakened almost on par with the fall in its share of the stock.

The paper uses a Beverton-Holt year class model with a Ricker recruitment function. The recruitment function is hump-shaped, implying that a too large spawning stock is harmful for recruitment. Strong density-dependence in the survival of eggs and larvae is a possible reason for this. It is shown that, for a stock being limited by carrying capacity at the pre-recruit stage rather than the post-recruit stage, one may expect a strongly asymmetric curve for sustainable yield as a function of total biomass. The biomass of an exploited population might possibly exceed the biomass of a pristine population under those circumstances.