Synergies between climate and management for Atlantic cod fisheries at high latitudes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 9; pp. 3478 - 3483
• Main Authors: Kjesbu, Olav Sigurd, Bogstad, Bjarte, Devine, Jennifer A., Gjøsæter, Harald, Howell, Daniel, Ingvaldsen, Randi B., Nash, Richard D. M., Skjæraasen, Jon Egil
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.03.2014; National Acad Sciences
• Subjects: Analysis of Variance; Animal behavior; Animals; Biological Sciences; Biomass; Biomass production; Climate; Climate change; Climate models; Cod; Conservation of Natural Resources - methods; Fish stocking; Fisheries - methods; Fisheries management; Gadus morhua; Gadus morhua - growth & development; Geography; Ice; Marine; Marine fishes; Mortality; Oceans and Seas; Population Dynamics; Population size; Productivity; Seas; Simulation; Barents Sea; PNE, Barents Sea; polar displacement; ocean warming; gadoids; population dynamics; quota
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1316342111

The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and positive changes in population size, this invariably leads to questions about whether favorable climatic conditions or good management (or both) were responsible. The Barents Sea cod (Gadus morhua) stock has recently increased markedly and the spawning stock biomass is now at an unprecedented high. We identify the crucial social and environmental factors that made this unique growth possible. The relationship between vital rates of Barents Sea cod stock productivity (recruitment, growth, and mortality) and environment is investigated, followed by simulations of population size under different management scenarios. We show that the recent sustained reduction in fishing mortality, facilitated by the implementation of a “harvest control rule,” was essential to the increase in population size. Simulations show that a drastic reduction in fishing mortality has resulted in a doubling of the total population biomass compared with that expected under the former management regime. However, management alone was not solely responsible. We document that prevailing climate, operating through several mechanistic links, positively reinforced management actions. Heightened temperature resulted in an increase in the extent of the suitable feeding area for Barents Sea cod, likely offering a release from density-dependent effects (for example, food competition and cannibalism) through prolonged overlap with prey and improved adult stock productivity. Management and climate may thus interact to give a positive outlook for exploited high-latitude marine resources.