UW Aquatic & Fishery Sciences Quantitative Seminar
University of Washington
Harvest Control Rules for Highly Variable, Environmentally-Driven Species: The Case of the Pacific Sardine
Coastal pelagic fish in upwelling systems around the world exhibit extreme variation in productivity, with long periods of very low or very high abundance alternating in pseudo-cyclical fashion. These patterns have natural causes, and occurred long before any exploitation of forage fish started. This uncertainty presents management challenges, as traditional assessment methods and management strategies implicitly assume that variability in stock productivity is caused mainly by fishing, which is an inappropriate assumption for many coastal pelagic species. Management of the northern subpopulation of Pacific sardine (Sardinops sagax) is unique in that it directly uses environmental information for setting harvest quotas. Since Amendment 8 to the Coastal Pelagic Species Fishery Management Plan, harvest rate of Pacific sardine has been set as a function of the sea surface temperature at Scripps pier, based on the relationship between temperature and recruitment. By request of the Pacific Fishery Management Council, the relationship between environment and recruitment was re-evaluated and found to be still valid. A management strategy evaluation then showed that for a highly variable stock like Pacific sardine, a harvest control rule including environment and a minimum population threshold below which no catches occur is both precautionary and optimal for long-term catches maximization.