Cross-basin analysis of lake whitefish and cisco recruitment dynamics in the Great Lakes

Taylor Brown (PhD student), Andrew Honsey, Brian Weidel (USGS), Suresh Sethi, Lars Rudstam, and others (funded by Great Lakes Fishery Commission)

Understanding the factors that regulate recruitment across spatiotemporal scales and biophysical gradients is critical for predicting how fish communities will respond to ecosystem change. Across the Great Lakes basin, lake whitefish and cisco populations are the focus of restoration and management targets. However, many populations have experienced a lack of consistent recruitment success in recent decades, with few exceptions. This project is investigating the important suite of factors driving recruitment variability across populations and species in collaboration with biologists from across the Great Lakes region. In 2024, we published a synthesis of current knowledge regarding which biophysical processes are hypothesized to be most important for driving contemporary recruitment between species, among lakes, and across life stages, and the mechanisms by which those drivers regulate recruitment at key life stages. We also completed an analysis of lake whitefish and cisco recruitment across the Great Lakes and Simcoe, which involved integrating 38 long-term surveys to reconstruct over half a century of recruitment dynamics and investigating the degree to which recruitment was synchronized between species, among lakes, and through time. Our analyses revealed that lake whitefish and cisco exhibit differential recruitment dynamics that are likely regulated by species-specific factors. Next steps for this project include finalizing our ongoing statistical analyses aimed at identifying which hypothesized biophysical drivers of recruitment best explain observed recruitment variability for each species across space and time. Collectively, this research contributes to our understanding of the status of contemporary lake whitefish and cisco stocks and the anticipated trajectory of the fisheries they support with continued ecosystem and climatic changes.