Cooperative Fish and Wildlife Research Units Program: Minnesota
Education, Research and Technical Assistance for Managing Our Natural Resources

The Great Lakes featured high abundances of Cisco (Coregonus artedi) until the early-1900s when their stocks began to collapse, with Lake Superior declining in the mid-1900s. Since that time, the stocks have rebounded in Lake Superior, although they once again appear to be in decline. The original decline in the mid-1900s was attributed to a variety of anthropogenic factors including overfishing, pollution, and introduced species. Even when stocks were abundant, it was noted that large spawning stocks did not necessarily lead to large recruitment classes and, similarly, small spawning stocks could sometimes result in large recruitment classes. Factors quantitatively linked to recruitment have been evaluated previously using Ricker stock recruitment models. We propose using three quantitative methods to investigate the relationship of biotic and abiotic factors with Cisco recruitment, including: (1) Multivariate Auto-Regressive State Space Models; (2) Empirical Dynamic Models; and (3) Bayesian Spatial Delta-glmm models. This work will be done in collaboration with local, federal, tribal, and state agencies working on Lake Superior. Our proposed outreach plan includes numerous meetings with stakeholders, presentations at professional societies, peer-reviewed publications, and quantitative workshops focused on teaching the three methods we will be applying. Building on hypotheses established by prior researchers, we will be looking at climatic and temperature variables, indices of predators, indices of competitors, indices of spawners, and measures of habitat quality.