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Monday, September 12, 2011

Sturgeon Get Help From New Reef

Lake sturgeon will find prime spawning grounds next spring thanks to a new reef underway  in the St. Clair River.  The reef is being constructed of limestone and other types of rock and is modeled after a reef installed three years ago at the head of Fighting Island in the Detroit River International Wildlife Refuge.  The Fighting Island reef was the 2008-2009 Featured Project of the Michigan Wildlife Conservancy and the first Canada-U.S. jointly funded fish restoration project in the Great Lakes.  The Conservancy was the only U.S. non-profit organization to make a substantial financial contribution to the Fighting Island Reef and also provided valuable technical assistance during the design and cost analysis phases of that unique project. 

The Conservancy is also playing a key role in the St. Clair River reef construction, administering a $75,000 construction grant from the U.S. Fish and Wildlife Service’s Coastal Grant Program.  The Conservancy is working with University of Michigan Sea Grant Program personnel as well as the Fish and Wildlife Service.  The total cost of constructing the reef will be more than $335,000.  Most of the cost is being covered by other federal grants which will also fund a long-term research project to evaluate the cost-effectiveness of reef building in the Great Lakes.

Once common and widespread, the lake sturgeon dramatically declined around 1900; it now has a limited distribution in the Great Lakes region, and is a threatened species in Michigan waters.  Inland populations in Michigan are sparse and restricted primarily to the Manistique, Menominee, Sturgeon, and Indian Rivers in the Upper Peninsula, and the Cheboygan River (including Burt, Mullet, and Black Lakes) in the Lower Peninsula.  Occasionally, sturgeon show up in other rivers such as the Kalamazoo, Grand, Muskegon and Saginaw.

Lake sturgeon spend a lot of their time in waters 20 to 40 feet deep.  They spawn in May or June in a variety of depths, typically 6 to 28 feet.  While on river spawning grounds, sturgeon often break the surface with porpoise-like jumps.  Females lay several hundred thousand eggs at a time, become sexually mature at 25 years of age and spawn every 4 to 6 years. Males mature at age 15 and spawn every other year.  Some individual sturgeon have lived 150 years.  Sturgeon feed on sand or muck bottoms where they suck in bottom organisms including crayfish, snails, and larvae of mayflies and other insects.

The new reef is located at the head of the Middle Channel in the St. Clair River delta.  Project planners with the U.S. Geological Survey and the U.S. Fish and Wildlife Service consider the site nearly ideal.  The water currents and bottom type are well-suited for reef construction.  The site is near an old coal cinder dumping grounds that lake sturgeon have been spawning on and just upstream from a large wetland complex which will ensure that larval sturgeon will be carried to good nursery habitat as they leave the spawning beds.

The St. Clair River historically served as an important spawning grounds for many other native species as well as sturgeon.  But channelization, loss of coastal wetlands, filling/armoring shorelines, water pollution, and dredging limestone bedrock and gravel caused the sturgeon population to drop to less than one percent of its former abundance.  Many conservationists doubted whether the area’s once famed lake sturgeon fishery could ever bounce back.  However, with improvements to water quality over the past 40 years, federal scientists have begun to test whether small, strategically-placed spawning reefs can benefit the unique species.  The Fighting Island reef’s success helped pave the way for the St. Clair River reef and this new effort may be a catalyst for a series of reef projects in the future.  Young sturgeon are already coming off the reef at Fighting Island and planners expect the St. Clair reef to also be successful.

The St. Clair River reef will likely benefit walleyes, whitefish, the endangered northern madtom  and other fishes in addition to sturgeon.  “We will continue to monitor the Fighting Island reef as well as thoroughly evaluate the St. Clair River reef,” said Jim Boase, a fisheries biologist with the U.S. Fish and Wildlife Service.  The slow growth and longevity of the sturgeon requires long-term studies to determine impacts of reefs on the population, but we will gradually gain important clues.”

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