Contemporary Spatial Extent and Environmental Drivers of Larval Coregonine Distributions across Lake Ontario

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Coregonine fishes are important components of Laurentian Great Lakes food webs and fisheries and are central to basin-wide conservation and management initiatives. In Lake Ontario, binational management objectives include conserving and restoring spawning stocks of cisco (Coregonus artedi) and lake whitefish (C. clupeaformis), but the spatial extent of contemporary coregonine spawning habitat and which environmental factors are currently important for regulating early life success lake-wide are not well characterized. In Spring 2018, we conducted a binational ichthyoplankton assessment to describe the contemporary spatial extent of coregonine spawning habitat across Lake Ontario. We further characterized a suite of physical, climatic, and biological variables hypothesized to influence coregonine early life stage success and regressed them against observed species-specific catches using GAMMs and multimodel inference to quantify the relative importance of biophysical drivers. Between 10 April – 14 May, we collected 1,092 ichthyoplankton tows and captured over 2,350 coregonine larvae, including in historical spawning habitats without recent catches of coregonine early life stages. However, over 95% of larval catches were restricted to the eastern basin and were dominated by cisco, with lake whitefish representing less than 6% of captured coregonines. Observed catches of both species were strongly and similarly associated with ice cover duration, but the importance of site-specific characteristics varied, such as distance to shore and site depth for cisco and lake whitefish, respectively. These results highlight the importance of climatic drivers operating at large spatial scales and of local environmental habitat characteristics reflecting species-specific niche differentiation that may act in concert to regulate early life stage success. Furthermore, strong regional and cross-species differences in larval distributions emphasize the importance of lake-wide monitoring for assessing the status of cisco and lake whitefish population trajectories.
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66 pages
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cisco; coregonine; early life history; Great Lakes; Lake Ontario; lake whitefish
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Rudstam, Lars Gosta
Sethi, Suresh Andrew
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Weidel, Brian C.
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Natural Resources
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M.S., Natural Resources
Degree Level
Master of Science
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Government Document
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dissertation or thesis
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