When you think of reefs, the Great Lakes don’t immediately come to mind; instead, most people picture the coral reefs associated with tropical waters and colorful fish. But Saginaw Bay once had many rock reefs, created by glacial activity, that provided an important type of habitat for the bay’s aquatic species. Over time, reef habitat was lost, buried by sediment due to logging, manufacturing and agricultural activity in the area. To restore this lost reef habitat, the DNR and many partner organizations worked together on a portfolio of reef habitat projects, including the recently completed Channel Island Reef.

A nearshore reef, Channel Island Reef is constructed in the bay near Channel Island (aka Spoils Island). It is made of natural rock that rises several feet from the bottom but still sits a few feet below the surface of the water. Locally sourced limestone was used, which creates crevices and ledges perfect for spawning fish to deposit eggs into and for young fry (newly hatched fish) to hide from predators. The reef will get lots of wave action, which will keep sediment from building up and wash oxygenated water over fertilized fish eggs, increasing their survival.

“Restoring rocky reefs can help make native fish species – like lake whitefish and walleye – more resilient,” said Jeff Jolley, the DNR’s Southern Lake Huron Fisheries Management Unit manager.

These species use reef habitat for spawning, making it essential for supporting strong fish populations, especially whitefish, which are in decline elsewhere in the Great Lakes.

Jolley said that while walleye are now thriving in the bay, much of the population currently relies on river spawning. That makes it vulnerable—if just one or two river systems experience a disaster, blockage or habitat decline, the effects could ripple across the entire population. By restoring and enhancing diverse spawning habitats, biologists aim to build resiliency into the population.

“It’s similar to diversifying an investment portfolio,” said Jolley. “Spreading the ‘risk’ across multiple spawning areas helps ensure the walleye population remains strong even if one site falters.”

In the coming years, fisheries biologists will study activity at the reef, learning more about how fish use the reef and its beneficial effects on the ecology of Saginaw Bay.

Learn more about the project: Channel Island Reef: Increasing fish spawning habitat and resilience in Saginaw Bay | Michigan Sea Grant.

Questions? Contact Jeff Jolley at 989-686-2678.