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.