Method overview
We compiled bottom trawl survey data of fish biomass across marine ecosystems in the North Atlantic and Northeast Pacific. We analyzed the effect of temperature, and other environmental variables, on fish community biomass in four different ways. Using structural equation modelling, we examined whether relationships between net primary production and demersal fish community biomass are mediated by temperature, food-web structure, and the level of fishing exploitation. Subsequently, we used an explicit trophodynamic modelling framework to compare and explore the robustness of our empirical results and relate it to past investigations of fisheries catch (Friedland et al. 2012; Stock et al. 2017). Both analyses are focused on the drivers of cross-regional variation in fish community biomass and are performed at large geographic scales. In a third analysis, we used wavelet-revised model regression to analyze finer-scale fish biomass variability, both across and within ecosystems. Lastly, we examined the effect of temperature on fish biomass within ecosystems over time using different recursive biomass and surplus production models.