Abstract
` Temperatures in the Gulf of Maine have increased over the past four decades and are influencing key biological processes of marine fishes. We examined relationships between key aspects of American plaice ( Hippoglossoides platessoides ) stock dynamics (i.e., recruitment, distribution, and growth) and environmental variables to explore the effects of changing ocean conditions. Time series of relevant environmental variables included sea surface (SST) and bottom temperature anomalies, Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), and Gulf Stream Index (GSI). Spawning stock biomass (SSB) was included in some models to represent density dependence. Generalized additive models (GAMs) were used to evaluate relationships between these independent variables and stock dynamics over time. Recruitment analyses (age 1 abundance and R/SSB) revealed significant relationships with AMO, suggesting positive recruitment under colder and slightly warmer than average regional SST conditions. Distribution shifts in mean depth and latitude were mostly significantly and positively related to NAO, bottom temperature anomaly, and SSB, indicating movement into deeper and more northerly waters with warming and increasing biomass. Growth analyses (weight at age and condition index) revealed a significant negative relationship with AMO, suggesting decreasing somatic growth with increasing AMO values (North Atlantic-wide SST). SSB and bottom temperature anomaly also exhibited a significant positive relationship with weight at age, suggesting increased somatic growth with increasing SSB and bottom temperature. These analyses demonstrate the likelihood that changing ocean conditions are influencing American plaice stock dynamics and could be used to inform climate-integrated stock assessment modeling for American plaice.