March 3, 2025
When lakes in the upper Midwest ice-over in the winter, it’s not just ice fishing enthusiasts who benefit. Coldwater fish species, like lake whitefish, may benefit from ice cover as lake ice is hypothesized to protect eggs from wind-driven currents and wave action. Consequently, changes in ice cover over time could potentially influence reproductive success of coldwater fishes in large lakes.
Lake whitefish are an economically and ecologically important species in the Great Lakes. They spawn in late fall and winter, and their eggs develop during winter and hatch in the spring. Winter storms can bring harsh waves that displace eggs or bury them under sediment, but these risks may be buffered by ice cover, leading to greater reproductive success for the fish. For some Great Lakes lake whitefish populations, reproductive success has been sporadic or has declined in recent decades. As a result, fishery managers are interested in understanding the factors that may influence lake whitefish survival and reproductive success.
Dr. Corbin Hilling of the U.S. Geological Survey (USGS) Great Lakes Science Center (GLSC) is leading a new research project funded by the Midwest Climate Adaptation Science Center to address this high-priority fishery management need. His interdisciplinary team of scientists recently launched fieldwork on Lake Erie to better understand the relationship between ice cover and hydrodynamics, or water movement, on lake whitefish spawning reefs. Dr. Cary Troy and undergraduate student Eli Bohlander of Purdue University, Dr. Lissa MacVean of the University of Michigan, and Dr. Sam Kelly of the University of Minnesota-Duluth are all part of the research team.
In December 2024, the journey to the field site began on the USGS Research Vessel (R/V) Muskie, which sailed from its winter berth in Cleveland to the USGS GLSC Lake Erie Biological Station in Huron, Ohio. At the station, research equipment was prepared, calibrated, and loaded onto the vessel. The R/V Muskie then sailed on through foggy conditions before arriving at Niagara Reef, part of the Western Lake Erie Reef Complex.
At Niagara Reef, the scientists and vessel crew members deployed three monitoring stations on the lakebed. Each station housed an acoustic Doppler current profiler, a tool which uses sound waves to measure characteristics of water movement, including current speed and direction, turbulence, wave height and period, and characteristics related to ice. Additional sensors measuring temperature, water depth, clarity, and light penetration were also appended to the stations to give a more detailed picture of the underwater environment. Dr. Hilling explained, “The data gathered by these instruments will measure hydrodynamics and other environmental parameters to better understand relationships among ice cover, lake hydrodynamics, and lake whitefish reproductive success.” The team also equipped each station with a remotely activated buoy that can be released at the end of the study period to aid in retrieval of the stations.
While the research team completed the equipment deployment, another USGS team surveyed adult lake whitefish in nearby using gill nets. The collection of spawning adult fish were present suggests the deployment of the monitoring stations was well-timed within the spawning window and that the stations will likely yield useful data throughout the winter while eggs develop. Another fortunate occurrence for the project is that ice cover on Lake Erie has been above average this winter; ice cover is uncertain on the lake from year to year but is critical to collecting relevant data for this project.
The research team is anxiously awaiting spring when they can retrieve the stations and begin analyzing data, but they intend to leave the stations in place to capture as much data as possible to support multiple needs of fishery managers. “We intend to continue data collection into the walleye spawning season, based on interest from our management agency partners,” Dr. Hilling said. Walleye are a popular sportfish in Lake Erie and, like lake whitefish, spawn on the Western Lake Erie Reef Complex, though they do so in the spring.
The results of this project will deepen our understanding of Lake Erie’s winter conditions with and without ice. This information can then support Great Lakes fishery managers in their efforts to maintain a resilient fishery by restoring or enhancing fish spawning habitats or populations in the most effective and efficient way possible.