Status and trends of the Lake Huron prey fish community, 1976-2025

The U. S. Geological Survey-Great Lakes Science Center has monitored annual changes in the offshore (depth > 9m) prey fish community of Lake Huron since 1976.  Assessment of prey fish populations in Lake Huron is based on a bottom trawl survey that targets demersal species (i.e., those predominantly or intermittently associated with the lake bottom) and an acoustic-midwater trawl survey that targets pelagic species and life stages.  Prey fish abundance and species composition in 2025 was generally consistent with trends observed over the past decade.  Overall status of main basin prey fish community was rated as ‘fair.’  Bloater (Coregonus hoyi) and Rainbow Smelt (Osmerus mordax) remain the first and second most abundant species in the main basin followed by Alewife (Alosa pseudoharengus), whose populations consist mainly of low numbers of age-0 individuals.  Abundance of Rainbow Smelt is higher, and abundance of Bloater lower, in Georgian Bay and the North Channel than in the main basin, which suggests dynamics of these species vary by basin.  Native sculpin communities consist primarily of Deepwater Sculpin (Myoxocephalus thompsonii) due to the reduced abundance and distribution of Slimy Sculpin (Cottus cognatus).  In contrast, biomass of the exotic Round Goby (Neogobius melanostomus) in 2025 was the second highest observed in the bottom trawl time series.  Evidence of strong Bloater and Rainbow Smelt year classes in 2025 and continued recovery by Cisco (Coregonus artedi) in the North Channel were interpreted as positive community trends, whereas growth and expansion of Round Goby populations and low species diversity of pelagic prey fish communities merit concern.  Use of complementary surveys (bottom trawl, acoustics) remains important for evaluating prey fish status in Lake Huron, where prey fish community dynamics vary by basin and prey fish responses to changing environmental conditions depend on species and/or habitat.