Management Strategies for Northeast Arctic Saithe: - should predation on herring be taken into account?

Abstract

The Norwegian Directorate of Fisheries has suggested a management strategy for Northeast Arctic saithe. Based on the assumption that a maximum sustainable yield is achieved at a fishing mortality below Fpa, a strategy targeting an F about 0.05 below Fpa was proposed and sent for public hearing. A strategy targeting a fishing mortality below Fpa will imply that the expected spawning stock biomass will be above Bpa. Taking into account that saithe is an important predator on commercial valuable prey stocks, some stakeholders were concerned that an increased spawning stock biomass would have its costs in the form of lesser output from fisheries based on the saithe’s prey species, especially Norwegian spring-spawning herring. Based on stomach samples of saithe, its consumption of herring was estimated. It was estimated what the herring consumed by saithe could have contributed to in the Norwegian herring fishery. Taking this into account, the long-term economic yield was estimated for different exploitation levels of saithe. The results indicate, viewing the combined economic output from the fisheries on saithe and herring, that there will be no economic loss in applying an F of about 0.05 below Fpa as a long time management target for the saithe fishery.