The Rainy River and Lake of the Woods are home to one of the few remaining lake sturgeon populations in northwestern Minnesota. After decades of low abundance, a recent tagging study by the Minnesota Department of Natural Resources (DNR) provides further evidence that sturgeon abundance is on the rise in this system.
The 2004 study was a cooperative effort among sturgeon anglers, Ontario Ministry of Natural Resources (OMNR), Rainy River First Nations and the Minnesota DNR. Sampling was done on both sides of the international border.
A total of 1,739 sturgeon were tagged from April 1 to May 31, 2004, to learn more about the current status of the fishery.
This study would not have been possible without the help of sturgeon anglers, who provided more than half of the fish that were tagged. Gov. Tim Pawlenty even got in on the fun, tagging a fish during the 2004 governor’s fishing opener on Lake of the Woods.
Mark-recapture studies such as this are used to estimate the number of individuals in a population by comparing the number of fish recaptured with the number of fish marked initially.
A total of 659 fish were captured and examined for tags from June 22 to Sept. 2, 2004. Eight of those examined were tagged. This provides a population estimate of 59,050 lake sturgeon. A study done by the OMNR in 1990 estimated the population at 6,500 fish. This confirms what anglers have been seeing and DNR test nets have shown; sturgeon abundance is increasing in the Rainy River and Lake of the Woods.
The tagging study provided additional information that can be used to gauge the health of the fishery and measure progress towards recovery. Fin rays were collected from more than 500 fish to determine ages. The age structure of the sample suggests that natural reproduction began improving in about 1970 and has been very consistent since then.
However, healthy populations should have fish up to age 70 in the population. The oldest fish sampled in 2004 was 38. Similarly, there are few big fish (mature females) in the population. Only 5 percent of those sampled were greater than 55 inches, which is about the size female sturgeon start reproducing. This shows that while abundance is improving, the population still has a way to go to reach its full potential.
“The results of this study provide reasons for cautious optimism for the future of sturgeon and sturgeon fishing in Rainy River and Lake of the Woods,” said Kevin Peterson, International Falls area fisheries manager.
“If the we keep harvests at sustainable levels and protect their habitat, sturgeon should continue their recovery. Sturgeon fishing will continue improving and anglers will encounter more large fish as the population of fish over 55 inches expands.”
Sturgeon harvest in 2004 was estimated at 5,112 pounds, which was below the target level of 7,600 pounds. However, sturgeon harvest the previous year (before regulations were changed) was approximately 20,000 pounds, which is not sustainable.
Additional monitoring is planned for 2005. Creel surveys will provide information on angling effort and fish harvest. Some additional tagging may be done on the lower river. Follow-up studies will evaluate tag loss and handling mortality. These studies will become part of the long-term monitoring program to assess the health of sturgeon stocks in Rainy River and Lake of the Woods.
Sturgeon management has come a long way since the fish were dried and used to stoke the boilers of steamships in the 1800s. Much work remains to be done.
“It’s not a coincidence that as the water quality of the Rainy River improved, sturgeon began to increase,” Peterson said. “Cleaner water and revitalized spawning habitat improved conditions for sturgeon as well as for those who live and recreate on the Rainy River,” Peterson said. “The progress shows that good things happen when people work together to protect and improve our natural resources.”
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