Fisheries crews from the Minnesota Department of Natural Resources recently wrapped up their annual assessment of spawning sturgeon on Lake of the Woods and Rainy River.
For a fisheries biologist, this is the glamorous part of the job, getting up close and personal with big fish that can tip the scales at 100 pounds or more.
"We just don't see fish like this in any of our other surveys," said Tom Heinrich, large lake specialist for the DNR in Baudette, Minn. "It's cool to see a big walleye, but big is 30 inches. That doesn't even make it on the sturgeon scale."
Sturgeon populations on Lake of the Woods and Rainy River are on the rebound after nearly being wiped out in the early 1900s by overfishing and declining water quality in the river where many of the fish spawn. Numbers have been increasing since the 1960s, when the United States and Canada enacted clean-water legislation that led to improved spawning habitat.
Slow-growing fish, sturgeon can live upward of 100 years and don't begin spawning until their teens.
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The DNR and Ontario's Ministry of Natural Resources earlier this spring announced the sturgeon population on the border waters has reached short-term recovery goals -- male sturgeon to age 30 and females to age 50, along with sturgeon larger than 70 inches and 30 age-classes in the population.
Heinrich said the annual spawning survey is a key tool in monitoring the population.
"A big part of what we're doing is measuring our goals toward complete sturgeon recovery," he said. "One of the outcomes of the sampling is we were able to show we've met our short-term recovery, and now we're working on the long-term goals."
Long-term goals include male sturgeon to age 40 and females to 70 years old, with 10 percent to 15 percent of the population longer than 80 inches. There also would be 40 year-classes of sturgeon in the population.
About the survey
As part of the most recent survey, Heinrich said, fisheries crews set nets near the mouth of the Rapid River at Clementson, Minn., where sturgeon stage to spawn. The Rapid River is a tributary of the Rainy River.
Crews also tag sturgeon as a way to estimate the population and track annual mortality. Since 1990, the DNR and Ontario's MNR have tagged about 6,500 sturgeon in various studies, Heinrich said, including 100 fish this spring; 3,405 of the tagged sturgeon were longer than 45 inches.
Based on the most recent estimate in 2004, there are about 60,000 sturgeon of 40 inches and longer in the population, up from 15,000 during the previous estimate in the early '90s. Plans call for repeating the population estimate every 10 years, with the next survey scheduled for 2014.
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Heinrich said he has received 1,779 reports of tagged sturgeon from anglers since tagging began, including 200 this spring; DNR crews have encountered another 525 tagged fish during population surveys.
Sturgeon mortality is very low, he said, so it is difficult to estimate over a short time span.
"Ten years is a short time in sturgeon management, while it is a whole generation for walleye," Heinrich said. "I really don't have a good idea of what kind of mortality rate sturgeon have. My best guess is perhaps as high as 5 percent per year, though I wouldn't be surprised if it was lower."
When conditions allow, Heinrich said crews also try to sample sturgeon in tributaries such as the Big Fork and Little Fork rivers farther upstream, but water levels this spring were too low.
"We like to explore new areas because it gives us an opportunity to sample a larger number of fish," Heinrich said. "It becomes very important when we do things like population estimates. The more fish we tag, the better off we are."
New targets
Heinrich said the biggest fish they sampled this spring was a 69½-inch female with a 31½-inch girth and an estimated weight of 93 pounds. They recaptured the sturgeon a few days later after she had spawned, and the girth had dropped to 21½ inches.
"That was quite a change," he said. "When you see a sturgeon out there that looks like a hot dog, you're probably seeing a recently spawned fish."
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Ontario doesn't allow sturgeon fishing in any provincial waters, but anglers on the Minnesota portion of Lake of the Woods and Rainy River can keep one sturgeon annually. The take is closely monitored, with a limited catch-and-keep season and a limit of one sturgeon annually. Anglers must buy a tag to keep a sturgeon, the fish must measure 45 to 50 inches in length and all harvested fish must be reported within 48 hours.
Heinrich said the DNR until recently managed the Lake of the Woods and Rainy River sturgeon fishery with a target harvest of 7,600 pounds annually. But with the population now at short-term recovery goals, he said, the target has increased to 11,600 pounds. The change won't affect seasons or limits, Heinrich said.
Dokken reports on outdoors. Reach him at (701) 780-1148; (800) 477-6572, ext. 148; or email bdokken@gfherald.com .
