Fish & Wildlife Today: Minnesota DNR

It’s early October, and John Lindgren has his hands full of small lake sturgeon. The DNR biologist, based in Duluth, has spent the last week tagging the 6-inch-long fish so they may be identified years later after release.

From a plastic tub, he carefully lifts what looks like the result of a shark mating with a sucker. It’s a goofy-looking fish. Lindgren, however, is enamored. “This is a perfectly evolved body design that hasn’t required changing since the Jurassic era, and I can’t imagine anything more beautiful.”

Five rows of overlapping plates, called scutes, run the length of the sturgeon’s body. On small sturgeon, the scutes can be sharp, so Lindgren handles each fish cautiously as he presses its snout into a short needle protruding from a lunchbox-sized device that inserts a 1-millimeter-long microtag.

“Every other year,” says Lindgren, “we’ll conduct fish population investigations on the St. Louis Bay, and by using a tag detector we’ll be able to determine if each sturgeon we net had been stocked as a fingerling or a fry, which are too tiny to microtag.”

Comparing the effectiveness of stocking sturgeon fingerlings to stocking fry is just one component of a project begun in 1983 to restore lake sturgeon to the St. Louis River estuary. So far, results of the stocking effort have been encouraging, and biologists are hoping that, within a few years, they will see some of the first naturally reproducing sturgeon on the St. Louis in more than 100 years.

Biologists are also reporting success with sturgeon recovery and restorations on other Minnesota waters, such as the Ottertail and Rainy rivers. Once beleaguered by pollution, dams, and overfishing, Minnesota’s sturgeon populations appear to be making a comeback.

Big and old

The largest freshwater fish in North America, the lake sturgeon is also the longest lived. A fish caught in Manitoba in the 1800s and photographed is estimated to be 14 feet long and 400 pounds. Specimens have been aged at more than 150 years. Like other long-lived animals, such as elephants, lake sturgeon reproduce late in life and infrequently. Females reach sexual maturity around age 25 and spawn only every four to eight years.

Reproducing at such a low rate, lake sturgeon are vulnerable to overfishing. Being migratory, they also need free-flowing rivers to reach shallow spawning waters. And relatively clean water is necessary for the survival of the vulnerable sturgeon young as well as sturgeon food such as mayfly nymphs.

Lake sturgeon populations throughout Minnesota plummeted in the late 1800s due to overfishing, dams, and pollution. On the Rainy River, the slow-growing sturgeon couldn’t reproduce fast enough to sustain a yearly harvest that reached over 1.75 million pounds per year. “The population crashed in the mid-1890s and didn’t begin recovery for more than 70 years,” says Tom Mosinday, a sturgeon expert with the Ontario Ministry of Natural Resources.

Sturgeon disappeared entirely from the Otter Tail River and other tributaries of the north-flowing Red River after a dozen dams built in the early and mid-1900s to control floods blocked the fish from reaching spawning waters on tributaries.

On the St. Louis, dust from sawmills covered the river bottom. When the organic matter decomposed, it sucked away dissolved oxygen in the water needed by baby sturgeon and invertebrates.

“In the 1890s there were 10 sawmills on the St. Louis River, sometimes set up right on the water,” says Lindgren. “By the beginning of the 20th century, sturgeon had been extirpated [made extinct] from the St. Louis River and western Lake Superior.”

Clean water led to recover

Recovery became possible in the early 1970s in large part due to clean water resulting from federal regulations. On the Rainy, sturgeon have also been helped along by netting bans. Minnesota closed commercial sturgeon fishing in the 1930s, and in 1995 the Canadian government finally bought out commercial operations. That same year the Rainy River First Nations Band of Ojibwe put a moratorium on its commercial fishing operation, which had been harvesting roughly 3,000 pounds of sturgeon each year.

In 1997, the DNR began transferring several hundred 20- to 30-inch (3- to 5-year-old) Rainy River sturgeon and stocking them on the Otter Tail River, a tributary of the Red River of the North, near Fergus Falls. In 2017, the females should reach sexual maturity and head upstream to spawning riffles. “We’re hoping they’ll come back up the Red to the Otter Tail,” says Arlin Schalekamp, area fisheries supervisor at Fergus Falls. “But that won’t happen until we can remove or bypass these dams.”

Dams on the Red River have been blocking sturgeon upstream migration for more than 60 years. But now the DNR and other agencies are working cooperatively with local communities to modify the structures.

Over the past several years, the DNR has built three fish bypasses on dams on the Red and the Otter Tail and other tributaries, with several more in the works.

Luther Aadland, a research scientist with DNR Ecological Resources who designed the structures, says a series of step pools and a corrugated culvert allow the fish to get through the dam and reach spawning riffles upstream.

Meanwhile, on the St. Louis Bay, biologists with the Minnesota and Wisconsin departments of natural resources have been stocking lake sturgeon since 1983. At first, the only sturgeon available were from Lake Winnebago in Wisconsin. Since 1997, however, Minnesota and Wisconsin have been raising sturgeon from the eggs of females netted in the Sturgeon River, a Lake Superior tributary in Michigan.

Eggs from Lake Superior fish are considered more genetically suitable for a Lake Superior restoration effort than eggs from inland Wisconsin sturgeon.

The Sturgeon River progeny will be stocked until 2002, with fry stocked some years and fingerlings others as part of an experiment to see if the less-costly fry will survive. Then biologists will discontinue stocking to see if stocked lake sturgeon are beginning to return to historical spawning areas to reproduce naturally.

“Already we’re hearing reports from anglers on the St. Louis that they’re hooking some big sturgeon in late winter around the spawning grounds,” says Lindgren. “We suspect those are some of the 16- and 17-year-old males, which reach sexual maturity earlier than the females.”

He says the male sturgeon are staying in the upper estuary in preparation for spawning in the spring.

“There probably aren’t any females yet, so the males will just have to wait,” Lindgren says. “But in a few years, we’re hoping that some reproduction will be occurring.”

After 2002, Minnesota and Wisconsin DNR crews will set up fine-mesh nets below likely spawning sites hoping to catch sturgeon fry drifting downstream. Lindgren can’t wait to see naturally reproduced sturgeon fry in their historic waters.

“One hundred years ago,” says Lindgren, “we drove the St. Louis River sturgeon population to extinction. And now, after 20 years of cooperation between fisheries management agencies, we are on the verge of re-establishing a self-sustaining population. That is a good thing.”

Editor’s note: Interested in knowing more about efforts to restore lake sturgeon in the Great Lakes basin? The U.S. Fish and Wildlife Service (USFWS) has created a new web site that consolidates information from various states, universities, and USFWS field stations working on sturgeon restoration and research.

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