By Kevin Bunch, IJC
Since 2004, nine artificial reefs have been constructed in the St. Clair and Detroit rivers. These reefs have aimed to replace fish spawning habitat destroyed decades ago when shipping channels were created. Even though there have been unexpected problems along the way, people involved with these projects say they’ve learned what worked and what didn’t and have applied those lessons to new projects.
The initial test reef was built in 2004 near Belle Isle on the Detroit River, with an eye toward boosting native fish populations – particularly lake sturgeon, lake whitefish, northern madtom and walleye, according to a report released in 2015. Since the 2004 project, the people behind those reefs now go through a more thorough process for siting and placement. This includes advice from sea lamprey control experts to make sure that habitat isn’t built for those species to spawn too, said James Boase, fish biologist with the US Fish and Wildlife Service. Fortunately, sea lampreys ignored the test reef, and have since been found favoring the natural reef near the headwaters of the St. Clair River.
The test reef also consisted of three kinds of rock. Based on monitoring data of fish spawning, successive reefs have settled on using 4-8 inch (10-20 centimeter) pieces of limestone for construction materials, being the most useful to native species. Limestone is also what the natural reefs consisted of along the rivers prior to the channels being dug out.
Siting is an important factor that has been refined over the course of several projects. Reefs have been built parallel to the water flow to reduce the risk of being disrupted from water or sediments washing downstream. But a 2012 artificial reef at the St. Clair River’s middle channel has been largely filled in by sediment in the years since it was built. Boase said about two-thirds of the reef there has been buried, though madtom catfish are continuing to use the remaining portions. Another reef built at Fighting Island in 2008 has seen similar problems with sediment on its eastern section.
“We’ve integrated (river expert) scientists from the University of Michigan and from the (US Geological Survey) folks out in Denver, Colorado, to assist with siting design, and looking at different reef shapes and locations within the corridor to prevent that (loss) from happening,” Boase said.
Ed Roseman, a USGS research fishery biologist, said those two reefs were constructed to go across the channel from shoreline to shoreline, in a bid to make sure that fish noticed they were there. Due to sediment plumes out of the Thames River in Ontario, however, silt was deposited in portions of the reefs.
The Fighting Island reef was expanded in 2013 toward the island side where sedimentation wasn’t an issue, following successful spawning of lake sturgeon, whitefish and walleye, said Claire Sanders, remedial action plan coordinator at the Essex Region Conservation Authority.
“It was successful almost immediately,” Sanders said. “It was an exciting project, with a huge number of partners, and was something that hadn’t been done before – at least on the Canadian side.”
Lake sturgeon require fast-flowing water and specific cobbled reef conditions for their eggs to stay oxygenated without being washed away. But moreover, fast-flowing water helps keep sediment from settling on the reef. Other native species that have been found spawning or using the reefs include white bass, suckers, smallmouth bass and trout.
Roseman said they’ve learned to study the hydrodynamics of the system to make sure the water won’t end up depositing silt or otherwise damage the reefs. There are ongoing studies to see if there is a way to affordably maintain and clean those buried Middle Channel and Fighting Island reefs on a regular basis – perhaps every two years – to give fish the opportunity to use them again, Roseman added. Scientists at the University of Michigan are researching if using high-pressure water jets to blast the sediment away would work, similar to technology used by ocean treasure hunters.
“There are a lot of reefs in the Great lakes and even beyond that could benefit from this,” Roseman said.
Money also needs to be taken into account on siting. The US Great Lakes Restoration Initiative (GLRI) has provided funds in the past for reef restoration projects, but those grants are only available for the work if the reef has been constructed within the US side of the waterway, Boase said.
The learning process continues, too – work is underway on a new reef near Historic Fort Wayne in Detroit. A test reef had been built in 2015, and is now being expanded to include another four acres. Boase said it’s a high-flow, deep segment of the river relative to other areas – about 40-55 feet deep – and freighter traffic periodically passes by overhead. That work should begin in fall 2017.
Boase said there were concerns initially that the ships passing by could cause the Fort Wayne reef to dislodge, but the test reef has remained intact and in great shape. US Geological Survey has been the lead agency in determining how water flows over that section of the river and the impact it has on silt and rock movement over time, while the US Fish and Wildlife (USFWS) has focused on how to best attract target species like sturgeon. USFWS also is providing money through its coastal program to purchase additional rocks for the reef. Once construction is complete, two years of assessments on how well it’s working are planned.
Looking ahead, there aren’t any other Detroit River reefs in the works, but Boase said habitat restoration lessons from those built so far are providing guidance for shoreline restoration around Celeron Island and Stony Island on the lower Detroit River.
Roseman said the lessons from the Detroit River also are being used in other locations. GLRI funds are being directed toward restoration of the Maumee River to restore lake sturgeon habitat there, first by restoring wetlands at the lower Maumee, building up a rearing facility to raise sturgeon fry and potentially adding artificial reefs. Veterans of the Detroit River projects are working with the US Army Corps of Engineers to help inform restoration work in the St. Marys River, helping determine the best way to release water through the Compensating Works (large gates that help make sure there’s ample water for ships to pass through the river) to promote fish spawning in the Main Rapids. And scientists around the Niagara River and even in the Baltics region of Europe have been in touch to see what worked in the Huron-Erie corridor for their own restoration projects, Roseman said.
Above all, he added, consistently checking the situation in the water before and after restoring reefs has potentially been the most vital lesson of all. There are dozens of other artificial reefs in the Great Lakes basin that weren’t monitored, and researchers don’t know what shape they’re in or if fish are even using them.
“The key thing is having a willingness to make a risky experiment,” Roseman said. “We didn’t know if fish were going to use these piles of rock material. The only way to figure out if they did was to monitor it.”
The work was done through the partnership of more than a dozen organizations and agencies, Sanders said, known as the St. Clair-Detroit River System Initiative. These include the IJC along with USGS, USFWS, Fisheries and Oceans Canada, environmental agencies for Ontario, Michigan and Ohio, the Essex Region Conservation Authority, the Ontario Ministry of Natural Resources and Forestry, and Environment and Climate Change Canada. Other partners include the Walpole Island First Nation, The Nature Conservancy, Wayne State University and the University of Toledo.
Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.