The discovery of a juvenile sturgeon on the St. Louis River on Wednesday morning offers more evidence that adult sturgeon probably are spawning in the river, said a fisheries biologist with the Minnesota Department of Natural Resources.
Biologists doing an annual assessment netting on the river found the 24-inch sturgeon in a gill net, said John Lindgren, DNR fisheries specialist senior at French River. According to his estimate the fish would be 7 to 8 years old. Because the last stocking of fingerling sturgeon in the river occurred in 2000, Lindgren said he believes the fish is the result of natural reproduction by adult sturgeon.
Lindgren said the find left him with two emotions.
“Joy,” he said. “And relief.”
Until now, just five tiny sturgeon have been found in the river, four in 2011 and one in 2013. All were fry, tiny fish just out of their egg sacs. The discovery of the 24-incher on Wednesday indicated that adult sturgeon may have been spawning for longer than biologists had expected.
“Almost certainly, it’s a naturally recruited fish,” Lindgren said. “We’d like to see a few more. We’d like to see far more of these young fish than we are.”
The Lake Superior and St. Louis River sturgeon population was effectively extirpated as a result of overfishing and pollution, Lindgren said. DNR officials in both Minnesota and Wisconsin worked together to stock about 145,000 fingerling sturgeon in the river from 1983 through 2000 to re-establish a breeding population But it’s a slow process. Adult sturgeon don’t mature to spawn until they’re 20 to 25 years old. Stocking was discontinued after 2000 so biologists could determine whether natural reproduction was occurring.
Brian Borkholder, a fisheries biologist with the Fond du Lac Band of Lake Superior Chippewa, had found the previous sturgeon fry in the river. He, too, believes the 24-incher found Wednesday probably is a product of the river. Some sturgeon drift in and out of the river, he said, but so far all of them have been adults.
The sturgeon found Wednesday was captured near Spirit Island. Despite being caught in a gill net, it was not injured and swam away when released, Lindgren said. A spine from the pectoral fin of the fish was taken so that biologists could officially age the fish, he said.
The successful spawning of sturgeon in the river may have been aided by a major habitat restoration project below the Fond du Lac Dam in August 2009, although the fish found Wednesday would have been spawned before that project, which was a joint effort between the Minnesota DNR and the Nature Conservancy.
