Expanding efforts to document and understand Great Lakes coregonine river spawning

Andrew Honsey (USGS, ahonsey@usgs.gov), Todd Hayden (USGS), Brian O'Malley (USGS), Marc Chalupnicki (USGS), Ralph Tingley (USGS), Chris Davis (OMNRF), Wendylee Stott (DFO), Matthew Herbert (TNC), Philippa Kohn (TNC), Jason Smith (Bay Mills Indian Community), Dimitry Gorsky (USFWS), Amanda Ackiss (USGS)

Our project team sampled five Great Lakes tributaries in fall 2022 and spring 2023 to assess evidence of tributary spawning by coregonines, such as cisco Coregonus artedi and lake whitefish C. clupeaformis. Specifically, we sampled the Chaumont River, Niagara River, Irondequoit Creek (all tributaries to Lake Ontario), Escanaba River (tributary to Lake Michigan), and Spanish River (tributary to Lake Huron). Our methods included electrofishing and environmental DNA sampling during the spawning period, larval sampling in the spring, and requests for citizen input (e.g., if coregonines were observed by fishers in tributaries). We discovered a spawning run of cisco in the Spanish River about 0.5-1.5 km downstream of the dam in Espanola, Ontario, Canada, the first scientifically documented spawning aggregation of cisco in a Great Lakes tributary since the 1880s. We have published a manuscript in the Journal of Great Lakes Research documenting and describing the demography and morphologies (body shapes) of this aggregation, and, herein, we present results of genetic analyses indicating that this aggregation is genetically differentiated from two lake spawning populations in northern Lake Huron. We also captured six lake whitefish in the Escanaba River (including the first female that had been captured in the previous five years), supporting the notion that a relatively small spawning aggregation exists there. Finally, we detected coregonine (likely lake whitefish) environmental DNA at multiple locations in the lower Niagara River. Collectively, these findings highlight the potential importance of tributaries as spawning habitats for coregonines and are useful for informing ongoing conservation and restoration efforts.