Water managers in the Rainy-Lake of the Woods watershed have worked to create ideal conditions to help lake sturgeon successfully spawn this year in the Rainy River.
Lake sturgeon are endangered or threatened throughout Canada and the United States due to historic overfishing and the species’ slow growth rate. In Minnesota and western Ontario, the species is considered “of special concern” and “threatened,” respectively. These designations essentially mean the species is uncommon and must be carefully monitored and managed to ensure populations don’t shrink.
“The population is a fraction of what it was historically 100 years ago,” said Matt DeWolfe, engineering adviser to the International Rainy-Lake of the Woods Watershed Board’s Water Levels Committee.
After years of stocking the river each spring with sturgeon fry from the Manitou Rapids Hatchery, however, the population has been on the rebound, reaching 92,000 in 2014. The annual spring spawning along the Rainy River is key to the population’s continued improvement.
The Rainy Lake system features a dam along the Rainy River. This dam controls flow in the Rainy Lake system, providing benefits to residents but also impacting the natural flows that, in turn, can impact the ecology of the system.
In the spring of 2013, operations of the dam at Rainy Lake sharply reduced flow into the Rainy River below, leaving sturgeon eggs along the river exposed to the air, resulting in egg loss. Following a review of what happened, the board’s Water Levels Committee created an informal arrangement to avoid similar events from occurring in the future.
Known as the Sturgeon Protocol, this approach brings together the committee, Ontario Ministry of Natural Resources and Forestry, Minnesota Department of Natural Resources, dam operators at Rainy Lake (Packaging Corp. of America and H2O Power), the hatchery and local anglers to actively monitor the status of the spawn and adjust dam operations, where feasible, to ensure stable flows during the critical stages of egg and fry development.
Under the protocol, water temperature data is monitored and distributed daily to committee members, agency representatives, Rainy River First Nation, the Sports Fishing Club and dam operators.
When two days of consecutive 12 degrees Celsius (53.6 Fahrenheit) water temperatures are reported, it’s extremely likely that sturgeon spawning is underway. This activates the role of the observers along the river, to verify that spawning is indeed happening and ensure that special attention is given to limiting outflow reductions from Rainy Lake.
In 2019, DeWolfe said water temperatures reached the target spawning range on May 31. Following confirmation of spawning by observers, and as flows across the watershed were in decline at that point, the committee directed dam operators to postpone planned flow reductions and maintain stable flows into the Rainy River in keeping with the protocol. DeWolfe said this continued until June 19, when observers indicated that risk to the spawn had passed.
DeWolfe noted that protocol is only needed when water flows into the river system are on the decline or relatively low, as safety and structural issues take precedence. Any directives by the Water Levels Committee are made taking into account other interests and the objectives of the Rule Curves for Rainy Lake, which are a band of water levels that dam operators try to maintain through the year by adjusting water flows in the system.
While there have not been any follow-up investigations to see if spawning was successful, DeWolfe said weather conditions were favorable this year, so it seems likely that the fish were able to successfully lay their eggs without exposure to air.