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Cisco assessment in Lake Ontario

Taylor Brown (MSc/PhD student), Suresh Sethi, Lars Rudstam, Brian Weidel (USGS), and others (Funded by USGS)

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. 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.  The 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. The paper from this project will be published in 2022 in the Journal of Great Lakes Research (Brown et al. 2022).