Abstract
Measures of an organism's weight at a given length are often considered reliable indicators of energy reserves or ‘condition’, which can be related to fecundity and risk of mortality. Understanding the impact of environmental change on fish condition may therefore inform sustainable management of human activities in marine ecosystems. We investigated how changes in Canadian Pacific waters may be influencing the average condition of 35 commercially, culturally, and/or ecologically important demersal fish species. Because the condition of mature male and female, and immature individuals differs in its implications for population dynamics, ecological drivers, and measurement variability, we analysed these three maturity groups separately. We estimated density distributions, calculated Le Cren's relative body condition deviations, modelled spatiotemporal change in these deviations, and generated density‐weighted annual indices of body condition. We used Bayesian Dynamic Factor Analysis to identify common trends across species and tested for correlations with environmental variables. For most species, warmer sea surface temperature and lagged North Pacific Gyre Oscillation appeared neutrally or positively correlated with condition. Only the immature condition was also strongly correlated with primary production, but this effect was equally likely to be negative (e.g., Pacific Spiny Dogfish, Lingcod, and Sablefish) as positive (e.g., Quillback Rockfish, Southern Rock Sole, and Spotted Ratfish). Our approach propagates uncertainty from condition estimation through to environmental correlations to provide both ecosystem‐level and species‐specific inference. Robust estimates of relationships between condition and environmental variables can inform ecosystem approaches to fisheries management, including short‐term forecasts of weight‐at‐age or recruitment.