A multi-model framework for evaluating and partitioning environmental change impacts on fish population dynamics: a case study with Lake Erie Yellow Perch

Environmental change influences fish populations through multiple demographic pathways, yet most studies either assess overall productivity without identifying mechanisms or examine individual processes in isolation. Here, we develop a multi-model framework linking environmental changes in population productivity to specific demographic processes. The framework integrates models describing environment-dependent recruitment, somatic growth, natural mortality, and surplus production. We apply this approach to yellow perch (Perca flavescens) in Lake Erie, where recent decades have seen substantial environmental changes, including shorter winter ice cover and reduced nutrient loading. Both ice-on duration and nutrient loading were positively associated with population productivity. Ice-on duration primarily enhanced productivity via increased recruitment and adult growth, while partially offsetting increases in natural mortality. In contrast, nutrient loading showed consistent positive effects on demographic processes, including higher recruitment, lower natural mortality, and increased adult growth. In turn, the combined effects of long-term reductions in ice-on duration and nutrient loading reduced yellow perch maximum sustainable yield by 40% during 1975-2020. Our proposed framework provides a structured approach for identifying the mechanisms linking environmental variability to fish population productivity.