Drivers of walleye, brook trout, and lake trout abundance in Québec lakes

Inland fisheries provide essential ecosystem services, yet they face growing threats from anthropogenic activities and climate change. To sustainably manage these fisheries under global change, understanding the main drivers of freshwaters fish populations is key. Since the late 1980s, the Québec government has conducted standardized gillnet surveys to monitor game fish species and their habitats. Here, we identified the main drivers influencing the abundance of walleye, brook trout, and lake trout. Through random forest models, we analyzed 662 lakes and 38 predictor variables, revealing that fish community composition shaped the abundance of the two salmonid species. The best model performance was for brook trout (R2=0.54), followed by lake trout (R2=0.46), and walleye (R2=0.44). Brook trout populations were larger in allopatric lakes, while lake trout abundances were smaller in association with large piscivores. On the other hand, climate was more important for walleye. The dominant explanatory variables varied across species, suggesting different ecological niches. Our findings deepen understanding of fish population drivers in Québec lakes, highlighting the need for management plans to consider fish community context.