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Saginaw Bay on the rocks

September 4, 2019

Historic rock reefs of Saginaw BayThe Saginaw Bay rock reef restoration project is the culmination of years of work to restore historic fish spawning habitat within inner Saginaw Bay. The first major step in this habitat restoration effort concluded in 2016 with the completion of a multi-year assessment of several potential reef restoration sites. This U.S. Fish & Wildlife Service funded project provided resource managers with the information needed to determine the feasibility of restoring rock reef habitat within Saginaw Bay. The results of the assessment found that conditions in the inner bay are suitable for restoration and helped to identify two reefs as priority restoration sites. With this finding, federal, state, and local partners are taking the next major step and constructing and restoring rock reef habitat at these reefs.

Historically, rock reefs formed in the Great Lakes as glacial deposits and provided important spawning habitat for many native fish species. This critical spawning habitat was largely lost within Saginaw Bay due to increased sedimentation resulting from land use changes including logging and agriculture. The loss of inner Saginaw Bay's rock reefs contributed to the collapse of Saginaw Bay's walleye fishery in the 1940s and impacted local populations of other species. This project will mimic these naturally-formed reefs by placing approximately 5,000 cubic yards of rock material at each restoration site. This will create an approximate one-acre pile of rocks rising between two to four feet from the lake bottom. The height of the rock pile may vary to ensure adequate water depth is maintained to prevent navigational hazards.

When complete, this project will restore a one-acre rock reef at both sites (restoring two acres in total). These restored reefs will create important spawning habitat for many native fish species including both spring (walleye, smallmouth bass, suckers) and fall (lake whitefish, cisco, lake trout, burbot) spawning species. During spawning, the gaps formed between the rocks will create a sheltered environment protected from predators where fish eggs can incubate. The goal of this reef restoration project is not simply to create additional spawning habitat, but also to help facilitate a resilient and diverse fish population and to serve as a demonstration project, which can be evaluated and used to help inform future reef restoration throughout the Great Lakes.

Funding for this project is being provided through a $980,000 U.S. Environmental Protection Agency (EPA), Great Lakes Restoration Initiative grant and a $20,000 Saginaw Bay Watershed Initiative Network grant. The Michigan Department of Environment, Great Lakes, and Energy is the grantee for the EPA grant. Restoration of the reefs is anticipated to occur during the 2019 construction season and be completed by the fall of 2019.

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