BAY CITY, MI - “Don’t get hit” reads one of the rocks getting dumped into Saginaw Bay to create a new underwater reef. The note painted on the rock is from a student who learned about the project in school.

Nearly 23,000 tons of rocks are being used to create the offshore reef in waters northeast of Bay City. The $1 million project aims to revitalize walleye and other fish populations in Lake Huron and Saginaw Bay.

When it’s finished, the reef will cover about 3 acres and provide a rocky habitat to promote fish reproduction.

Sediment covers much of the bay’s bottom, a legacy of the area’s logging and agricultural industries.

15 Rock reef being built on Lake Huron

Walleye that lay their eggs in Saginaw Bay seek out rocky structure left by glacial deposits. When that habitat grew scarce, walleye eggs were left vulnerable and populations decreased rapidly.

According to DNR Fisheries Specialist David Fielder, the walleye population was also decimated by pollution in the 1940′s.

However, walleye numbers are on the rise today. Fielder said better land-use practices, environmental laws that cut pollution and years of stocking fish have helped to restore the fishery.

Saginaw Bay is home to about 5.5 million walleye age two or older, the DNR estimates.

“Most of the walleyes in Saginaw Bay spawn in rivers. Historically, Saginaw Bay had both reef spawners and river spawners. Today, we principally just have the river spawners left,” Fielder said. “What we’re trying to do is diversify the sources of reproduction and, in doing so, that generates more resiliency in the population.”

When walleye only spawn in rivers, a whole generation can be wiped out by river flooding or other environmental factors, Fielder said.

Planning and studying to determine if a rock reef would work in Saginaw Bay dates back to the 1990′s, Fielder said.

Man-made rock reefs are nothing new, especially in the Great Lakes. Rock reefs have been installed in Lake Michigan for cisco, in the Detroit River for sturgeon and already in Lake Huron for lake trout.

The site in Saginaw Bay chosen for reef restoration, the Coreyon reef, was picked after a 2016 study funded by the U.S. Fish and Wildlife Service showed that areas in the inner bay area suited for reef restoration and construction.

The reef will be about 5 feet tall in waters that are 18 to 21 feet deep. Though most boats should be able to navigate safely and there are far shallower areas in the bay, Fielder said the Coast Guard will have alerts out to warn mariners of the change.

Originally, two rock reefs were planned for the bay, but the project went forward with only the Coreyon reef.

Workers are placing 10 barges of limestone and two barges of glacial rock at the site to replicate a reef and are using GPS to track location and rock height.

The state of Michigan was granted $980,000 by the EPA for reef restoration in 2018 and a $25,000 grant from the Saginaw Bay Watershed Initiative Network. Michael Jury of the Michigan Department of Environment, Great Lakes, and Energy is the project manager for the reef and said the bid for the construction came in at $1,379,740. Funding to supplement the grants will come from the Office of the Great Lakes. Construction is underway and is expected to take 20 days to a month to complete. Construction is operating 24 hours a day.

Lake Huron Coordinator for Michigan’s Office of the Great Lakes Bretton Joldersma has been on the reef restoration project for around four years and helped coordinate the financing for the project. He said a rock reef today in the bay has a fair shot at lasting.

The passing of the Clean Water Act in 1972 and local efforts to keep sediment in the watershed on land has altered conditions in such a way that the new reef is expected to avoid the demise of its predecessor, Joldersma said. Members of the project are eager to see what fish will use the reef.

“I think that part of the experiment that we’re hoping to learn from.” Joldersma said. “There have been some improvements and we verified that through a modeling that indicated based off circulation patterns, the location of the reef that we’re restoring is in a place where we don’t see high sedimentation.”

In order to educate and inspire stewardship with local residents, members of the project went to classrooms to talk with students about the reef. Some students drew on rocks that are going into the bay and some made signs for construction.

Allison VanDriessche who teaches science at Western Middle School in Bay City said her students loved getting firsthand experiences of science happening in their own community. She said they highly enjoyed having field workers such as Fielder come into the classroom and allow them to participate in the project by designing signs.

“It gave them the opportunity for stewardship. It’s going to be their Saginaw Bay. It’s going to be their community and they’re a part of helping to restore some of the native habitat,” VanDriessche said. “I know that they all go home and they talk to their parents and then the parent’s community becomes educated as well and I think that’s also powerful, kids teaching their parents.”

Fielder said he was happy to go into classrooms of young people in the area and show them how even the big Great Lakes that have been here long before them and will be here long after, still need them.

“It’s really important that student and upcoming generations understand that these resources as big and vast as they are still require a great deal of caretaking stewardship and investment,” Fielder said. “They’re going to take over for us someday so they need to understand these things.”

Stewardship and monitoring will be the name of the game, Jury said. Efforts to fund studies to monitor what fish are using the reef and what it’s done for reproduction is the next step.

“If it’s successful we’d certainly want to build additional reefs in the bay. It’s going to be quite amazing,” Jury said. “It’s been a real labor of love and here we are finally, as I’ve told people, we’re close to getting out the champagne, we’re pretty darn close.”