Environmental Influences on American Plaice (Hippoglossoides platessoides) Stock Dynamics.

Behan, Jamie¹, Lisa Kerr², ¹Gulf of Maine Research Institute, ²University of Maine

Over the last 40 years, northwest Atlantic waters have warmed at a rate more than three times the global average and the recent decadal warming in this region is among the fastest in the world. Fish population dynamics are strongly influenced by these changing ocean conditions and Northeast groundfish have exhibited sensitivity to changing thermal conditions with associated changes in productivity and distribution. We used generalized additive models (GAMs) to examine relationships between key aspects of American plaice (Hippoglossoides platessoides) stock dynamics (i.e., recruitment, distribution, and growth) and ocean climate variables. Time series of relevant environmental variables included sea surface (SST) and bottom temperature anomalies, Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation, and the Gulf Stream Index and were related to time series of stock variables. Recruitment analyses revealed significant, curvilinear relationships with AMO, suggesting higher recruitment under colder than average and between 0.1-0.2°C regional SST anomaly values. Distribution analyses revealed significant and mostly positive trends with bottom temperature anomaly and stock biomass, suggesting that plaice are shifting into deeper waters and more northward with increasing bottom temperatures and stock biomass. In analyses of growth over time, AMO was the most consistent significant variable with evidence of decreasing growth in American plaice with increasing AMO. These analyses provide insight on how changing environmental conditions are influencing American plaice stock dynamics. This research is critical to moving toward climate-informed stock assessment for American plaice and was used to inform the most recent stock assessment.