Within the Laurentian Great Lakes, lake whitefish Coregonus clupeaformis metapopulations have fluctuated in size over the last 100 years driven by habitat degradation, sea lamprey predation, and unsustainable harvest (Jensen, 1976, Wells and McLain, 1973). To our knowledge, this represents the first documentation of successful lake whitefish larval production from Green Bay tributaries and suggests tributary spawning populations contribute to the greater abundance of lake whitefish observed in recent years. We estimated tributaries produced 452,000 larvae in 2017 and 721,000 larvae in 2018. Larval production was documented on each tributary using active trawl ichthyoplankton sampling, and larvae were observed outmigrating to open water environments. Locations of egg deposition mirrored areas of high observed fish densities. Spawning areas consisted of cobble substrates, and site-specific fish densities were primarily correlated with river flows between 0.3 and 1.0 m/s, with specific values varying by tributary and year. Highest abundance of adults was observed in the month of November as temperatures declined below 8 ☌. Here, we use hydroacoustic imaging along with egg and larval surveys to evaluate this novel riverine spawning in 20. Many knowledge gaps still exist with respect to the chronology of adult river migrations, including the physical characteristics of upstream habitats selected for reproduction and the extent of larval production by these riverine ecotypes.
Furthermore, after over 100 years of extirpation, adult lake whitefish are found spawning within major Wisconsin tributaries to Green Bay. Lake whitefish ( Coregonus clupeaformis ) within the waters of Green Bay, Lake Michigan have recently shown a substantial increase in abundance.
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