Another attempt to restore ‘dinosaur fish’ in St. Louis River – Duluth News Tribune

Along the street. LEWIS RIVER — The goal for the past 40 years has been to restore a population of Lake Superior’s native sturgeon, which call the river here home, but despite years of stocking, that has yet to happen.

Biologists from the Minnesota Department of Natural Resources and the U.S. Fish and Wildlife Service stocked 375 6-inch-long sturgeon in the mouth of the river at Duluth’s Chambers Grove Park — the first stocking of sturgeon in the river since 2000 — in hopes they will grow… Great and helpful. Population enhancement.

Another 375 sturgeon are going to the Fond du Lac area of ​​Lake Superior Chippewa for stocking in the upper St. Louis River.

The prehistoric fish, which has been part of Lake Superior’s ecosystem for thousands of years, could live for 100 years and grow to 100 pounds. Sturgeon, once cherished by indigenous people here, have been decimated by dams, pollution, overharvesting and habitat destruction on the rivers where they spawn and spend their first years — not just in the Twin Ports but in most rivers surrounding the Great Lakes and Minnesota. . They disappeared, and were extirpated, by the early twentieth century.

More than 145,000 estuary sturgeon were stocked here over a 13-year period between 1983 and 2000, and many of these fish are thriving, growing slowly and becoming large. Some are more than 60 inches long. But they have not reproduced well yet; They do not produce enough juvenile sturgeon to push the population to a self-sufficiency level.

Contributed/Minnesota DNR

“The guideline now is we probably need 25 years of stocking to bring back sturgeon around Lake Superior, and we’ve only been at 13, so the idea is to do more stocking over the next several years,” Dan Wilfond said. , the Minnesota DNR state fisheries biologist who is heading the effort.

Because sturgeon do not reproduce every year, even when they reach maturity, it will take a larger number of adult fish to ensure that each year’s offspring, called year-class, are large enough to maintain the population.

“We just need more of them to get this work done,” Wilfond said. Fisheries biologists call it better recruitment.

Jed Carlson / Superior Telegram

All 375 juvenile sturgeon stocked here — taken from the Sturgeon River in Michigan’s Upper Peninsula — are equipped with small internal tags that, if recovered, will allow biologists to wave a scanner over the fish and know not only when it’s been caught. It was stored but also if it was male or female. Officials hope to install a device in the river that will allow them to track the fish without having to catch them every year.

Over the next few years, thousands of additional sturgeon will come from the sturgeon river where the remaining population has always held up and is now doing very well.

Gary Meader/Duluth News Tribune

“I think the Sturgeon River was far enough away to avoid a lot of the problems other rivers have seen,” said Ed Baker, a biologist with the Michigan Department of Natural Resources. “It has very good numbers of sturgeon, and there are enough to allow us to share.”

Baker noted that fish using the Sturgeon River have more than 45 miles of river to spawn before reaching the dam, and have a large outfall into Lake Portage, which is warmer and more fertile than Lake Superior.

Crews cast nets into the sturgeon river in May, caught recently hatched baby sturgeon, then raised them over the summer in tanks. Some of these fish also go to the Fond du Lac Band of Lake Superior Chippewa for stocking in the upper St. Louis River, above hydroelectric dams, and to the Ontonagon River in the UP.

In the coming years, crews plan to take the sturgeon out of the Michigan River and milk them for thousands more fry, then raise them in hatcheries over the summer with up to 3,000 fish stocked in the St. Louis Estuary each fall.

Jed Carlson / Superior Telegram

For years it was thought that lake sturgeon would begin to reproduce here at age 25 for females and 15 for males, as they do in many other river systems. But many of the sturgeon in the St. Louis Estuary are now past that age and are still not breeding well. Biologists now say that many sturgeon take many years before they begin laying eggs.

In 2017, for example, of 138 sturgeon caught near Fond du Lac Dam by DRC officials, only three were female. Some research has shown that female sturgeon only lay eggs once every three to five years even after they have matured.

“We’re dealing with almost the coldest and least fertile lake in the world, so it may take longer for females to reach full reproductive maturity,” Wilfond said. “We’ve had some natural reproduction. It’s not enough.”

Jed Carlson / Superior Telegram

That’s frustrating for Lake Superior sturgeon advocates as they watch sturgeon in warmer, more fertile places throughout the region — such as the Rainy River, the Red River to the north, Big Stone Lake in Minnesota and the Wolf River system in Wisconsin — all getting bigger. Faster and reproduces at younger ages.

Wilfond also noted that early sturgeon stocking in the 1980s occurred while the St. Louis River was still largely polluted, before cleanup efforts had fully taken hold, especially efforts to better treat industrial and residential wastewater.

“The river was still quite turbulent when the first sturgeon were stocked, and it was probably unsuccessful in those first few years,” Wilfond noted.

The good news is that an extensive study of sturgeon tissue conducted by scientists found little to no problems with ancient contamination that lingers in the river sediments, things like PCBs, mercury or other chemicals that might thwart reproduction.

“These legacy contaminants are not the problem, which is good news,” Wilfond noted.

Jed Carlson / Superior Telegram

Sturgeon spawn in April below the Fond du Lac Dam on the river. Some live in the river most of the year, while others migrate to Lake Superior and spread along the south shore to Chequamegon Bay.

Although fishermen have been unintentionally catching and releasing sturgeon into the St. Louis River for many years, it became legal to target the species starting in 2015. All sturgeon caught by fishermen must be released into the river. Anglers have caught sturgeon at least 60 inches long, and Wilfond has caught them up to 67 inches long.

Renewable storage efforts were scheduled to resume in 2019, but were hampered by several factors, from flooding along rivers to bureaucratic errors to the COVID-19 pandemic. Now the effort appears ready to take off again.

“We’ll know they’re breeding well when we start catching more (naturally bred fish) than our stocked fish,” Wilfond said. “We’re looking forward to it. But with sturgeon, it’s a long game. We’re in this for the long term.”

Jed Carlson / Superior Telegram

The Fond du lac of Lake Superior Chippewa has been stocking sturgeon in the upper St. Louis River, above a series of dams, for 25 years. Band biologists hope the river’s relatively warm waters will allow these fish to reproduce at a younger age than those that call Lake Superior home.

“We’re excited about it, and we think we should see some spawning very soon,” said Erik Torvinen, a fisheries biologist with the band’s Natural Resources Division.

Crews have already seen 44-inch sturgeon swimming between dams downstream in Cloquet and as far upriver as Island Lake Dam on the Cloquet River and as far as Floodwood on the St. Louis River.

“They move around and do well. They use a lot of different habitats,” Torvinen said.

Contributed by the Fond du Lac Band of Lake Superior Chippewa

Trovinen noted that band members who catch sturgeon while fishing for other species collaborate with biologists to report the location and size of the fish after it is released. As is the case with estuarine sturgeon in Minnesota and Wisconsin waters, it is illegal to keep any sturgeon in the St. Louis River system.

Biologists have placed a scanning device in the river, which will record whenever a tagged sturgeon crosses, providing data on the age and sex of each sturgeon. This will help biologists track how long and where the sturgeon are surviving.

“Sturgeon are a culturally important traditional food source for the people of Fond du Lac, and are also important for ceremonial harvest,” Torvinen said. “So bringing these fish back is a very big deal.”

The lake sturgeon is a primitive fish with a cartilaginous skeleton, according to the Minnesota DNR. It has five rows of prominent bony plates, called scutes, on its body. Lake sturgeon have a flattened snout that bears large, bristle-like sensory organs called barbels. The fish’s soft mouth is located at the bottom of the head.

Sturgeon feed by gently dragging their arms along the bottom in search of prey. Their diet includes insect larvae, other invertebrates, snails, leeches, small mussels, and small fish.

The lake sturgeon, sometimes called the living dinosaur of the fish world, is a remnant of an ancient and primitive group of fish that nearly disappeared from Minnesota in the early 1900s. During the 19th century, sturgeon were considered a nuisance fish because they easily penetrated commercial fishing nets. They were taken out of the rivers and lakes they inhabited and piled up on the shores like logs; Sturgeon were also used to power steamboats because their meat has a high oil content. In the late 19th century, sturgeon eggs were recognized as a delicacy. They were harvested by the thousands for caviar until their numbers crashed in the early 1900s. This dramatic harvest combined with major habitat changes around sturgeon spawning areas has driven nearly the entire U.S. population to extinction.

Lake sturgeon are listed as a species of special concern in Minnesota and have strict harvest regulations.