Mapping Lake Michigan Spawning Reefs
TNC and our partners completed a report mapping spawning reefs for whitefish and other species in Lake Michigan
The word “reef” may conjure images of tropical corals and brightly colored marine life, but reefs are important structures in the cold water of northern Lake Michigan, too. Like their coral cousins, Lake Michigan’s rocky reefs provide critical spawning and forage structure for native lake species including lake whitefish, lake trout, walleye and cisco.
Great Lakes fisheries managers and natural resources agencies have recognized the importance of reef restoration to rebuilding fish populations, but little was known about their overall distribution and condition in the lake. The Nature Conservancy, working with the Michigan Department of Natural Resources, the Grand Traverse Band of Ottawa and Chippewa Indians, and the U.S. Geological Survey this year completed a comprehensive multi-year study of spawning reefs in northern Lake Michigan to inform future reef restoration efforts.
Analyzing navigation charts, historic fish spawning reports, and mapping data from NOAA, and gathering data from underwater cameras and on-site dives, the team identified core habitat and produced detailed maps of 27 potential spawning reefs. The maps detail the size and physical characteristics of the reefs, the fish that use them and other species observed, including invasive species like quagga mussels, round gobies and rusty crayfish.
Invasive quagga mussels have blanketed the Great Lakes bottomlands and filter out the food that young fish need to grow from eggs to adults. Stocks of lake whitefish and cisco have plummeted as they’ve been deprived of food at critical growth stages, while invasive rusty crayfish and round gobies eat native fish eggs. Combined with our efforts with partners to restore tributary spawning behavior for whitefish, reef restoration can help rebuild populations of whitefish and cisco by giving them a place to spawn and grow.
Whitefish and cisco are essential native species to the Great Lakes ecosystem, which also contribute to communities which rely upon them, including Tribal and non-Tribal commercial fishers, markets that sell and restaurants that serve whitefish, and the cultural tradition of eating whitefish in lake communities.
Up until now, studies of spawning reefs have focused on individual reefs, like the Elk Rapids Reef we helped restore with many of the same partners in 2015. This study helps us scale our work from a single reef to inform restoration efforts at the system level across the Great Lakes. The study filled critical information gaps needed by agencies and fisheries managers to prioritize and plan reef restoration projects for the fish that need them and the people who rely upon the fish.
Explore the Great Lakes
Great Lakes Fisheries
In the Great Lakes, native fisheries are the foundation of a $7 billion commercial and recreational fishing industry, as well as a living indication of the health of the entire freshwater system.
Returning Whitefish to the River
On the banks of the Jordan River, scientists and conservationists work to revive river-spawning lake whitefish, aiming to restore the Great Lakes ecosystem and support local communities.
The Search for Lake Whitefish
Spend a day in the field with TNC Conservation Fellow Alex Verdeja-Perez as she journeys in the rain and snow in search of lake whitefish—a crucial species for the biodiversity of the Great Lakes.