Paul Simonin, Lars Rudstam, Patrick Sullivan, Donna Parrish (Univ. Vermont, USGS), Bernie Pientka (Vermont Fish & Wildlife), Allison Hrycik, Tim Mihuc (SUNY-Plattsburgh), (Funding from Champlain Sea Grant)
Alewife invaded Lake Champlain in the early 2000s and this project was created to study the interactions between nonnative alewife and native rainbow smelt. Historically, rainbow smelt were the primary food for native salmonids and walleye, and the primary predator of native mysids. Lake Champlain is also one of the few lakes where rainbow smelt are native, and where they spawn in the lake and reach uniquely large sizes. We studied the effect of alewife on rainbow smelt using stage structured and spatially-explicit models of predation and cannibalism. Differing amounts of spatial overlap between adults and young-of-year, and associated differences in cannibalism and predation on larvae, are the likely mechanisms explaining the increase in alewife in this system. However, a large year-class of rainbow smelt was observed in the main lake section of Lake Champlain in August 2014, suggesting alewife are not displacing rainbow smelt entirely. Our model predicts that this will be the case, because cannibalism rate is a function of fish densities and overlapping distributions of adult and young of each species, and thus large adult populations will lead to increased cannibalism rates. This understanding of rainbow smelt-alewife interaction will help explain the dominance of alewife over smelt in other Great Lakes, and assist with forecast of future population densities. Project results are being shared with state and federal management agencies in New York, Vermont and throughout the Great Lakes region.