Impact of an Environmental Index of Recruitment on the Stock Assessment for Petrale Sole ( Eopsetta jordani Lockington, 1878) in the California Current Ecosystem

ABSTRACT Stock assessments provide key scientific input for managing fisheries. Age‐structure information is important for these assessments because it provides the foundation for estimating recruitment, which impacts estimates of future spawning biomass and other assessment parameters that inform management. For some species, like petrale sole ( Eopsetta jordani Lockington, 1878) along the US West Coast, the younger cohorts are poorly sampled, which leads to uncertainty in estimates of recent recruitment. We used recruitment deviations from the most recent petrale sole stock assessment and oceanographic indicators derived from the GLORYS oceanographic model to develop an environmental index of recruitment. We then tested the impact of including the index in the assessment using Stock Synthesis. Quadratic relationships for degree days during the larval stage and alongshore transport during the pelagic juvenile stage explained 66% of the variation in recruitment deviations for 1993–2018 (the training period). We then included the index predicting the 2019–2022 (forecast period) recruitment deviations in the assessment model and compared the output to the 2023 base model without this index. Including the index provided information to capture recent recruitment variability and improved near‐term forecasting, leading to more accurate estimates of recruitment, spawning biomass, and projected catch—assessment estimated quantities that inform management decisions.