Conflicts in Science and Management: The Case for Pacific Sardine

Pacific sardine is a dynamic population that undergoes natural boom-and-bust cycles. Despite sardines’ ecological and economic importance, the variability that governs population changes remains poorly understood. Understanding the influence of oceanography on the life history, migration, and population dynamics of sardines is important for fishery management. Over the history of the California Current sardine fishery, numerous studies have attempted to explain why the US and Mexican portions of the sardine biomass off the West Coast should be divided into Northern (Cold - NSP) and Southern (Temperate - SSP) subpopulations. Since 2015, a habitat model including a Sea Surface Temperature (SST) threshold has been used to delineate subpopulations. The assessment and management of the NSP is conducted by the US (using an SST threshold of 16.7° C), while that of the SSP is conducted by Mexico (using a threshold of 17°C). Meantime, new population genetics and stock structure studies have found that the reproductive ecology of Pacific sardine reflects a single, panmictic population spread over a wide geographic range and influenced by environmental forcing, suggesting that assumptions regarding the two-subpopulation hypothesis be reconsidered, along with the influence of oceanography on sardine population dynamics. The implications of finding a single sardine population are significant, as this could result in a review of current US fishery management policies and reference points used to set the annual fishing quotas. In this paper we discuss the importance of the California Current’s influence on the population dynamics of sardine, current fishery management, and management implications.