The need for ecosystem based fisheries management is well recognized, but substantial obstacles remain toward implementing these approaches given our current understanding of the biological complexities of the ecosystem along with the economic complexities surrounding resource use. This study develops a multispecies bioeconomic model that incorporates biological and technological interactions to determine the optimal catch and stock size for each species in the presence of a nuisance species. The nuisance species lowers the value of the fishery by negatively affecting the growth of the other species in the ecosystem, and has little harvest value of its own. The populations of arrowtooth flounder (nuisance species), Pacific cod, and walleye pollock in the Bering Sea/Aleutian Islands region of Alaska are used as a case study. This study empirically estimates multispecies surplus production growth functions for each species and uses these parameters to explore the impact of a nuisance species on the management of this ecosystem. Using dual estimation methods, multiproduct cost functions are estimated for each gear type in addition to a count data model to predict the optimal number of trips each vessel takes. These functions are used, along with the estimated stock dynamics equations to determine the optimal multispecies quotas and subsidy on the harvest of the nuisance species to maximize the value of this three species fishery.
As approaches for ecosystem-based fisheries management are developed, it is important not only to focus on the species with harvest value, but also on species which may have no harvest value on their own but affect the productivity and availability of higher value species. As arrowtooth flounder is a low value species and has a large negative impact on the growth of cod and pollock, it is optimal to substantially increase the harvesting of arrowtooth, lowering its population resulting in increased growth and harvesting in the two profitable fisheries. Ignoring the role of the nuisance species results in a substantially less productive and lower value fishery than if all three species are managed optimally. This study highlights the role of both biological and technological interactions in multispecies or ecosystem approaches for management, as well as the importance of incorporating the impacts non-harvested species can have on the optimal harvesting policies in an ecosystem.
