FARGO - Old is new again in Big Stone Lake.

The narrow, 26-mile long lake along the Minnesota-South Dakota border about 125 miles south of Fargo-Moorhead recently got another influx of lake sturgeon, a prehistoric-looking fish common to Big Stone's waters for centuries before water-quality degradation and damming of the Minnesota River that flows out of the lake caused their demise.

"They were native to the lake, but the last ones we saw in the lake were probably in the 1940s," said Minnesota Department of Natural Resources fisheries biologist B.J. Bauer, based in Ortonville. "So this is pretty cool."

The DNR and the South Dakota Department of Game, Fish and Parks have partnered since 2014 to reintroduce sturgeon to Big Stone. They stocked 4,705 fingerlings in the lake Aug. 30. That's in addition to 21,174 sturgeon stocked from 2014 to 2017.

With bony plates along their back and a long, slender body that goes from a bullet-shaped head to a shark-like tail, lake sturgeon have been described as "armored torpedoes." They are bottom feeders, eating insect larvae, worms, leeches and other small organisms.

And, no, sturgeon are not a threat to walleyes. They have a sucker-like mouth on their flat bottoms and rarely eat fish.

That doesn't stop sturgeon from growing to monstrous sizes. The Minnesota record is a 94-pound, 4-ounce behemoth caught from the Kettle River in 1994. An angler set the state's catch-and-release record last spring with a 73-inch sturgeon from the Rainy River, a popular early-season destination for anglers trying to catch a once-in-a-lifetime fish.

Bauer said DNR records show a lake sturgeon netted in 1911 was eight feet long and weighed 236 pounds.

The sturgeon stocked in Big Stone aren't anywhere near that size yet - and may never be, of course - nor is there a legal season on them. Anglers on the popular walleye and perch lake, though, have been catching sturgeon incidentally the past couple of years and Bauer said DNR crews netted a 25-inch long fish last fall.

"They are growing fast. They show up in our nets when we are doing surveys and we see pictures anglers have when they catch them accidentally," Bauer said. "We're sort of in uncharted waters here. We had an expectation based on other lakes how fast they would grow, but Big Stone Lake is very productive and everything grows fast. It will be fun to see how big these sturgeon will get."

The re-expansion of sturgeon into Minnesota lakes and rivers is a conservation success story. Historically common in many lakes and bigger rivers, they were nearly eliminated from the state because of water pollution and damming of rivers. Sturgeon need free-flowing rivers to migrate to good spawning areas.

In Big Stone's case, it was a combination of both. Located in a heavy agriculture area, the lake's waters became too turbid from decades of runoff. And dams on the Minnesota River, which flows from Big Stone's south end, prevented sturgeon from swimming into the headwaters.

Now, though, the lake's waters have become clearer with changes in land use.

"The lake is cleaner. There's more vegetation. Things have really changed," Bauer said.

It was a similar story to many other bodies of water like the Red River that flows through Fargo-Moorhead, Otter Tail Lake and the Otter Tail River, Big Detroit Lake. All were once prime lake sturgeon territories where the fish disappeared because of dams, loss of habitat, pollution or overharvest.

The DNR in the late 1990s put together a long-range plan to re-introduce sturgeon to their historic area. The Red River, Otter Tail Lake, five tributaries and six other lakes have been stocked with 2.6 million sturgeon in a cooperative effort between the DNR and the White Earth and Red Lake Indian nations.

Henry Drewes, the DNR's regional fisheries manager based in Bemidji, has said removal of dams was one of the most important steps in the sturgeon's recovery.

"To date we have restored over 400 miles of river as a free-flowing stream in the state of Minnesota," he told the Minnesota Conservation Volunteer magazine last year.

Big Stone Lake isn't in the Red River watershed, but sturgeon have taken enough of a foothold that news of an angler catching one barely moves the needle anymore.

"It's becoming more and more common," Bauer said. "It's kind of neat because when individuals started catching some of these fish, we'd get a picture in the office and it was very exciting. Now, it's sort of like, 'Yeah, it's just another fish.' We love it and we know the anglers are excited to catch them, but it's not so much a rarity anymore."