After months of frozen stillness, mercifully warm sunshine sweeps across the North Country, melting thick sheets of lake ice, causing waters to mix and churn and turn over. In a nearby forest, spring raindrops fall, first hitting the tree canopy, then cascading pinball-style down through leaves and branches, and finally soaking into the spongy soil. The filtered rain is gradually fed back into deep, clear lakes, many of which are home to a shimmering silver fish called the tullibee.
Since its inception, the Tullibee Lake Watershed Forest Stewardship Project has resulted in hundreds of landowners contacted, and nearly 200 of them have received low-cost private forest stewardship plans for a total of more than 20,000 acres. It also has provided over $100,000 in financial assistance for private land enhancements, such as tree planting and erosion control, that benefit water quality.
Each new stewardship plan costs the landowner a flat fee of $200, which is 40 to 70 percent less than the typical cost, depending on the size of the property. Included in the plan are things like which tree species to plant, which stands to thin, and when. The forester who writes the plan can also advise on how to set up a sustainable timber harvest to generate income and improve forest health. Armed with a stewardship plan, a landowner may then choose to enroll in Minnesota's Sustainable Forest Incentive Act. The program provides an annual payment of $7 per acre to owners who set aside 20 or more qualifying acres of forest land for at least eight years.
Link in the Food Chain
The tullibee, a member of the salmon family, is a rich and high-energy food for large game fish. The DNR analyzed 3,713 northern pike from 112 Minnesota lakes to learn how factors such as available prey species affect growth rates of the toothy predators. "We found a clear indication that the larger pike were being grown in lakes with tullibees," says Pete Jacobson, DNR fisheries research supervisor. "At a certain size, pike in these lakes switch from primarily eating yellow perch to eating tullibees, and then their growth rates really take off." Trophy pike appeared to benefit from the same cool, well-oxygenated water tullibees need to survive.
Veteran Leech Lake fishing guide Al Maas knows firsthand the importance of tullibees to big muskies. When late summer conditions cause tullibees to die off, muskies go on the prowl. "If you go into these areas and watch your graph, you'll see those muskies sitting right underneath the schools of dying tullibees," Maas says.
Since the 1950s, Maas has witnessed changes in tullibee abundance. "I don't see the numbers anywhere near what they used to be," he says. He has also noticed a trend toward smaller tullibees and fewer large "humpbacks" that used to be a common catch during ice fishing season. On the bright side, Maas reports that Leech still holds a sizeable tullibee population, and their numbers may have even increased over the last couple of years. "That's good news for big pike and muskies," he says.
Minnesota has about 650 tullibee lakes, more than any other state in the lower 48. Many of these waters are prized by anglers because tullibees (also known as ciscoes, or lake herring in Lake Superior) provide a high-energy feast for walleye, northern pike, muskellunge, and lake trout. Changes in land use and climate are causing many lakes to lose tullibees. Keeping forested land intact can help maintain water quality in lakes with tullibees and other cold-water species. That's why the Department of Natural Resources Forestry Division launched a special project. The Tullibee Lake Watershed Forest Stewardship Project is engaging owners of private woodlands and other conservation partners to protect vulnerable waters in north-central Minnesota.
Pete Jacobson, DNR fisheries research supervisor, has been studying Minnesota's declining tullibee population since 2006. "The statewide decline has been rather steady for the last 30 years," he says. "Average statewide abundance, as measured by our survey nets, has declined by about 60 percent over that time period."
Jacobson cites two main threats to tullibees. The first is climate change because it is warming the waters of this cold-water species. The second is eutrophication of lakes. With an influx of nutrients like nitrogen and phosphorous running into lakes from the surrounding land, algae and other aquatic plants proliferate and deplete oxygen. The combined effects of these two threats can cause large numbers of tullibees to die during late summer.
"In the spring of the year, when the water turns over, that's when a deep lake gets all of its oxygen in the lower depths," Jacobson explains. Once the surface water warms, the upper and lower layers of the water column become stratified by temperature. Dissolved oxygen below the middle transition layer, or thermocline, is locked away until the water turns over again in the fall.
This deep-water oxygen vault is vital to tullibees. They can't tolerate warm surface water—76 degrees is lethal and 54 degrees is optimal—so from roughly June until September, they need to stay deep. Trouble is, the oxygen down there can run out by late summer, especially in lakes that contain excessive algae.
"If a lake has too many nutrients coming in, algae thrive near the surface," Jacobson says. "When the algae dies, it literally rains down into the deep water, decays, and sucks out all the oxygen." Tullibees then become sandwiched between the lethally warm surface layer and the asphyxiating depths of the lake, a predicament known as oxythermal stress.
If climate change continues to extend the summer season in Minnesota, limited supplies of cool, oxygenated water will have to last longer each year. Good tullibee habitat is bound to disappear from many lakes—but not all of them. The DNR conducted a joint study with University of Minnesota professor Heinz Stefan and colleagues to identify cold-water refuge lakes that should be able to support tullibees several decades from now. The researchers predicted that 176 Minnesota tullibee lakes will continue to harbor enough dissolved oxygen and cool water temperatures during late summer when tullibees are most likely to die of oxythermal stress. The refuge lakes are spread throughout much of northern Minnesota, from deep within Superior National Forest to the outskirts of St. Cloud. The future of tullibees in the state depends on keeping these high-quality lakes clear of oxygen-depleting nutrients, and this is a prime function of healthy forests.
What's in a Watershed? DNR fisheries researchers have found that phosphorous levels, which spur algae growth in lakes, increase significantly if the watershed has more than 25 percent disturbance from urban or agricultural use.
Development in a watershed poses a risk to water quality, particularly when forest cover is replaced by lawns, roads, and impervious surfaces that send nutrient-laden sediment or fertilizers straight into lakes when it rains.
"From forest stewardship plans to perpetual easements, there are all kinds of tools out there to help landowners," says Gary Michael, DNR private forest management supervisor. "And if we can keep 75 percent of the watershed as a working forest, then we reduce the threat to tullibee."
DNR aquatic habitat specialist Heather Baird knows water quality is largely affected by land you can't see from the dock.
"If we only focus on the shoreline and walk away, we're missing an important piece of the puzzle—and that's the watershed," says Baird. Water drains into a lake from land that can stretch miles into the surrounding landscape.
Watersheds in the popular vacation area of north-central Minnesota contain forested tracts of private land, which could be developed. Therefore, urgent conservation efforts are underway in Aitkin, Becker, Cass, Carlton, Crow Wing, Hubbard, Itasca, and Otter Tail counties.
"This is an area of the state where we still have several lakes with really good water quality and fish habitat, but yet there is driving pressure to develop the land," says Baird. "If we don't act now, the opportunity might be lost to protect these lakes before the watersheds become disturbed."
Private Land Solutions. In late 2011, the Minnesota Forest Resources Council began to collaborate with DNR fisheries and forestry staff on how to increase private forest management within tullibee watersheds.
"Keeping forested lands forested—especially those on privately owned lands, which are the most at risk of conversion or development—keeps fish in our lakes and wildlife in our watersheds, and provides wood for our mills," says Lindberg Ekola, the council's landscape program manager. "And we know that when we give landowners the right tools to manage their properties, they are much more likely to keep the land forested instead of selling or developing it."
The Tullibee Lake Watershed Forest Stewardship Project began in 2013 with funding made possible by the Clean Water, Land and Legacy Amendment. The project helps pay for private land management within the watersheds of 64 tullibee refuge lakes. DNR Forestry oversees the project in partnership with the Board of Water and Soil Resources, which enlists local soil and water conservation districts to contact landowners, answer questions, and sign up interested parties.
Working Forest. Jim Ballenthin knows his trees. The retired Twin Cities attorney owns 260 acres of mixed forest land on Ponto Lake at the headwaters of a Cass County watershed that also includes Girl Lake, a tullibee refuge lake. With funding from the project, he recently hired a private forester to update the stewardship plan for his property.
Ballenthin contracted a logging company to harvest 13 acres of aspen to benefit golden-winged warblers. He's also had selective thinning done on stands of white pine and white spruce. These and other improvements have helped boost wildlife habitat while ensuring the forest contributes to a healthy watershed.
Now he and his wife are considering a permanent conservation easement. The DNR, along with other agencies and nonprofit groups, enters into easement agreements with willing landowners who retain ownership and agree to keep the land forested.
"We'd like to keep the land the way it is and allow it to be a working forest in perpetuity without any development on it," Ballenthin says. "We feel it's important to do our share to ensure this world is a better place, while we're here and after we're gone, than it was before we came."
Other Partnerships. Lindsey Ketchel, executive director of the Leech Lake Area Watershed Foundation, works with conservation-minded landowners like Ballenthin to protect watersheds. She expects development interest in the region to increase. "There are going to be a lot of people who are retiring and will be converting their cabins to year-round homes or bigger homes. We know these things are coming," she says. "The encouraging part is, with a little a bit of resources, we can go a long way toward sustaining the water quality of these really important recreational lakes."
In 2014 the foundation launched a program called Clean Water Critical Habitat, using a grant from the Outdoor Heritage Fund to purchase permanent conservation easements from landowners within the watersheds of 38 tullibee refuge lakes. Each watershed has less than 25 percent land disturbance, making 75 percent protection an attainable goal.
In a related effort, the DNR is working to secure permanent working forest easements within the watersheds of five tullibee refuge lakes: Ten Mile Lake in Cass County, Kabekona and Big Sand in Hubbard County, and Big Trout and Pelican in Crow Wing County. Known as Minnesota Forests for the Future, the easements allow sustainable timber harvesting while permanently protecting the land from development. The Outdoor Heritage Fund is providing support for this project.
The Anderson family's cabin overlooks the south end of Kabekona Lake. Nestled behind it are 34 acres of aspen forest they plan to enroll in a Forest for the Future easement. Graced with a labyrinth of former logging trails and aptly named spots like "grouse corner," the land holds special meaning for Per Anderson. He and his siblings decided to preserve it as a tribute to their late father, Albert, who was passionate about conservation. "It's just an amazing opportunity to invest in a sense of place and fulfill our father's desire to make sure the land was always protected for the right reasons," says Anderson.
DNR Forestry identified the property as having high conservation value, since it borders the Paul Bunyan State Forest and is just a stone's throw from Kabekona Lake, a 133-foot-deep tullibee factory. The lake's most recent fisheries survey turned up more than 20 tullibees per net, nearly 10 times the statewide average.
"The thing I love about the program is that it has the requirement for a management plan that goes with it," says Anderson. "So you don't just acquire some value, but you're also taking on a commitment to a science-based plan for the conservation and improvement of the land."
It will take much planning and commitment to sustain healthy tullibee populations in the coming decades. Fortunately, many private landowners have already realized this simple truth: How we treat our lands is how we treat our waters. And with their help in keeping forested watersheds intact, tullibees may continue to haunt the depths of Minnesota lakes.