Assessing ecosystem-scale synchrony in Atlantic cod body condition

During the 1990s, the marine ecosystem around Newfoundland and Labrador experienced a regime shift following significant fluctuations in bottom-water temperatures and heightened fishing pressure. This study investigates the relationship between bottom-up processes and stock productivity as indicated by body condition of Atlantic cod ( Gadus morhua) across Northwest Atlantic Fisheries Organization Divisions 2J, 3K, 3L, 3N, 3O, and 3Ps from 1977 to 2021. We use generalized linear mixed-effects models applied to body weight measurements from bottom-trawl research surveys, to analyze variation in body condition across space, time, and size categories. Quantifying changes in condition across multiple cod populations can help identify broader trends in condition attributed to environmental change. We found regional stock synchronicity, suggesting that broad factors such as environmental temperature variations and capelin abundance greatly influenced the 1990s and mid-2010s biomass declines. Condition in April, May, and June showed large declines following the 1990s, possibly due to changing spatiotemporal overlap with prey. The smallest cod (15–30 cm) had lower condition compared to larger cod. Condition research across stocks enhances our understanding of the environmental mechanisms contributing to survival, ecosystem productivity, and drivers of stock resilience.