The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior

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The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior

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Invasive species are a global problem, impacting property, habitats, ecosystem function, and native species. Our ability to predict future habitat and spread of aquatic invasive species is limited because it is challenging to collect and integrate information regarding life history, movement, and habitat, especially across continents. Ruffe (Gymnocephalus cernua), a demersal, invasive fish, has caused substantial ecological damage. Given the potential for ecological impacts, such as native fish declines, ongoing concern regarding the spread of Ruffe in the Laurentian Great Lakes is warranted. But there are significant research gaps regarding life history, movement, and Ruffe distribution in the native and non-native range. Therefore, the overall goals of my dissertation were to acquire life stage-specific data for Ruffe, including dispersal, seasonal, and spawning movements and characterize their life cycle and to develop a lake-scale species distribution model at 30-m resolution. Regarding the first goal, I found that Ruffe has characteristics that allow them to adapt to a range of environments, including rapid maturation, relatively long life and large size, batch spawning, genotypic and phenotypic plasticity, tolerance to a wide range of environmental conditions, broad diet, and multiple dispersal periods. To address the second goal, I developed a species distribution model for Lake Superior because Ruffe has established in the lake but is not yet widespread. I found that a variety of species distribution models constructed to predict Ruffe suitable habitat based on environmental data resolved to a variety of scales all performed similarly but varied substantially in the area of habitat predicted, particularly the offshore habitat area classified as suitable. I conclude that to interpret the outputs of the Ruffe species distribution models, both model performance and the ecology of Ruffe must be considered to better characterize its fundamental niche. Broadly, I demonstrate the importance of synthesizing the life stage-specific biology and distribution of an invasive species with species distribution models to advance our ability to predict the future habitat of an invasive species.


University of Minnesota Ph.D. dissertation.December 2017. Major: Biological Science. Advisor: Joel Hoffman. 1 computer file (PDF); xi, 207 pages.

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Gutsch, Michelle. (2017). The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior. Retrieved from the University Digital Conservancy,

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