In situ evaluation of spawning lake whitefish eDNA detection in Lake Michigan’s Green Bay

Grant: # 1987

Grant Amount: $27,606.23

Board Decision Year: 2022

University of Wisconsin - Stevens Point - College of Natural Resources (Stevens Point)

College of Natural Resources

Homola, Jared ([email protected]) 517-214-7039

2022 Ecosystem Health and Sustainable Fish Populations: Ecological and Biological Research to Inform Management - Ecological and biological fisheries research to inform management

Project Details

Lake whitefish populations in the lower Great Lakes have generally experienced recruitment declines, with the southern Green Bay, Lake Michigan fishery remaining the most stable. Recently documented successful lake whitefish spawning in Green Bay tributaries cannot fully account for local abundance estimates, suggesting open-water reef spawning may be contributing substantially to local populations. This study explores the feasibility of using environmental DNA (eDNA) to identify these critical, yet unknown, spawning locations. We hypothesized that elevated eDNA concentrations would correlate with lake whitefish aggregations, allowing us to infer spawning site locations using spatially explicit modeling to hindcast eDNA sources. We conducted field sampling in Green Bay during spring and early summer, collecting water samples near the lake bottom to approximate spawning period conditions. Ambient eDNA concentrations were quantified at 50 randomly selected sites, establishing a baseline to differentiate aggregation-related spikes. Additionally, we sampled around commercial trap nets, serving as proxies for spawning aggregations, at varying distances and directions to characterize eDNA dispersal patterns. Our results revealed spatial heterogeneity in ambient eDNA concentrations, with an average ambient lake whitefish eDNA concentration of 11.9 pg/L in southern Green Bay. Sampling around trap nets demonstrated elevated eDNA concentrations, often forming detectable plumes. A Gaussian kernel model estimated that 68% of eDNA was within 3318 meters of the source, with a baseline concentration of 4.11 pg/L. Maximum likelihood models that incorporated fish biomass and dispersal dynamics accurately predicted eDNA distributions and source location with a precision of 46 meters. This study demonstrates the potential of eDNA as a viable tool for locating lake whitefish spawning sites in Green Bay. By combining eDNA sampling with hydrodynamic modeling, we can efficiently identify highprobability aggregation areas, guiding subsequent confirmatory studies such as egg sampling. Future research should focus on developing more sophisticated hydrodynamic models to improve spatial and temporal resolution, enabling broader application of eDNA surveys for targeted conservation and restoration of lake whitefish spawning habitats in the Great Lakes.

 

The final report for this project can be accessed at this link: final report