Working with partners to restore lake sturgeon to the Ontonagon River
August 8, 2018
A young lake sturgeon that was reared in a streamside rearing trailer on the Ontonagon River in the Upper Peninsula of Michigan. Photo by USFWS.
Once an abundant resource, the Ontonagon River lake sturgeon population is now the focus of an exciting multi-agency restoration effort. We at the U.S. Fish and Wildlife Service are partnering with the Michigan Department of Natural Resources, Ottawa National Forest, Upper Peninsula Power Company, Fond du Lac Band of Lake Superior Chippewa, Keweenaw Bay Indian Community and U.S. Geological Survey to help bring these magnificent fish back to the river.
The Ontonagon River is one of the largest rivers along the south shore of Lake Superior in the upper peninsula of Michigan. For nearly 10,000 years lake sturgeon from Lake Superior ascended its turbid waters each spring to spawn over rock and boulders left by the retreat of glaciers. This once vibrant and diverse fishery was eventually extinguished by a multitude of factors including over-harvest, habitat loss, degraded water quality and the construction of dams, which impeded fish passage.
The Michigan Department of Natural Resources initiated lake sturgeon stocking in the Ontonagon River in the late 1990s, but assessment work by our biologists starting in 2005 revealed that these efforts were largely unsuccessful. This is in part due to the vulnerability of young lake sturgeon to degraded habitat and water quality, and predators.
The migratory nature of lake sturgeon created an additional hurdle to recovery efforts. It is now known that lake sturgeon will imprint on their birth waters, and in 15 to 25 years when they are sexually mature, will return to the same rivers where they were born to spawn. Therefore restoring lake sturgeon back to the Ontonagon River meant that biologists had to not only protect young lake sturgeon, but also create a rearing environment where they could grow and imprint in water from the river.
In 2013, partners placed a streamside rearing unit built by our staff from Genoa National Fish Hatchery on the west branch of the Ontonagon River to improve survival rates of newly hatched lake sturgeon. A streamside rearing unit is a retrofitted trailer that protects young sturgeon in a controlled environment. A pump system connects the trailer to the river and is used to circulate river water through the trailer’s fish tanks.
Each year since the construction and placement of the streamside rearing unit, our staff from the Ashland Fish and Wildlife Conservation Office work with partners to collect and fertilize eggs from the nearby Sturgeon River, rear sturgeon in the trailer, tag each sturgeon raised, and eventually release the fish into the Ontonagon River.
Preliminary findings are encouraging. In 2016, 25 of the largest lake sturgeon reared in the trailer were tagged with small acoustic transmitters. They were then released along with 500 other young lake sturgeon at two locations within the Ontonagon River, more than 20 miles from Lake Superior. Of the 25 stocked sturgeon that were outfitted with the transmitters, more than half of the fish were found to have reached the river mouth at Lake Superior within a month of stocking. The findings demonstrated that young lake sturgeon reared in the streamside trailer were successfully navigating the river and finding their way out to the lake where they will live and grow into adulthood.
Today, work continues to gather information about the movement of lake sturgeon in the Ontonagon River and evaluate the progress of stocking efforts. Sturgeon recently captured in gill nets set off the mouth of the Ontonagon River in Lake Superior were outfitted with acoustic transmitters and released back into the wild. Over the next 10-years their movements will be tracked by acoustic receivers set along the shoreline of Lake Superior from Duluth, Minnesota to Sault Ste. Marie, Michigan. Work also continues to monitor for sturgeon stocked in the late 1990s, which are now reaching maturity and are expected to return to the river to spawn. Our staff also conducted a spring spawning run assessment in the Ontonagon River this year in which three large, but non-spawning, lake sturgeon were captured. This is one of several hopeful signs that the river’s historic sturgeon population may one day return.