Date

Fall 2025

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Anticipating climate-change impacts on fisheries requires understanding how marine species respond to future ocean conditions. The productivity and abundance of fish populations are largely shaped by the survival of early life stages, which are highly sensitive to ocean conditions. Variation in ocean conditions can influence early stages of fish species by influencing reproductive output of adults and/or larval health, survival, and retention. The goal of this study was to understand how oceanographic variables can impact reproduction and recruitment of a nearshore rockfish species, gopher rockfish (Sebastes carnatus), helping to forecast potential climate change impacts on the population. I assessed historical relationships between estimated gopher rockfish recruitment from the stock assessment model, and regional biogeochemical variables, physical drivers, and large-scale climate indices. The Pacific Decadal Oscillation (PDO) was the most consistent and significant predictor of recruitment, particularly during the late gestation and early larval periods in March. Warmer, more stratified conditions during positive PDO phases were associated with elevated dissolved oxygen (DO), pH, and temperature in nearshore waters, which in turn coincided with increased year-class strength. Results from the first chapter support the hypothesis that source water properties, particularly DO, pH, and temperature, are likely to influence adult fish health, thereby affecting total larval output and year-class strength. The second chapter of this thesis presents a laboratory study designed to examine the influence of low DO and pH on total larval production of gestating female gopher rockfish. A log-linear model incorporating maternal length and a combined stressor of pH and DO reveal that maternal body size scaled exponentially with fecundity and exposure to lower DO/pH conditions significantly reduced fecundity. When these results were extrapolated to the population level, the log deviation between the environmentally informed models, which incorporate the influence of pH and DO on fecundity, and length-only models accounted for 21–26% of the variation in historical recruitment deviations, highlighting the potential role of oceanographic conditions in shaping year-class strength via total larval output. When the same total larval output model is projected into the future, there is a 10-30% decline in population level total larval output by the end of the century. These findings highlight the importance of incorporating environmental drivers into fisheries models to better understand and predict population dynamics under changing ocean conditions.

Download

Share

COinS