By Chris Niskanen
Muskies live atop Leech Lake's piscatorial food chain, but the inimitable game fish is a bottom-dweller -- a creature of the lake's plant beds. "All life stages of the muskellunge have some association with aquatic vegetation,'' says Jerry Younk, Department of Natural Resources fisheries research biologist.
Female muskies lay eggs in chara, a genus of algae. Large chara beds serve as nurseries for muskie fry and fingerlings that bulk up on insects and minnows. When they become adults, the predatory muskies hang out in shallow aquatic plant beds, or what many anglers call "cabbage."
When Al Maas, who has fished for muskies on Leech Lake for 40 years, talks about the disappearance of "lake weeds," his voice reflects a personal loss. A Leech Lake bed of native vegetation is a treasured muskie haunt for Maas; when one disappears, it's as if a familiar neighborhood has been razed for freeway expansion.
"The Big Pelican Island weedbed is gone,'' Maas says. "The Gull Island weedbed is gone. The Cedar Point weedbed -- gone. Several small weedbeds by Bear Island -- they're gone too. They've all disappeared since I started fishing."
The loss of Leech Lake aquatic plants is no longer just one angler's lament. Maas' prized aquatic plant beds are playing a prominent role in a new conservation project that proposes a better way for protecting critical aquatic habitat in and around Minnesota lakes. Leech Lake has become the crucible for a new way of managing lakeshore development.
The need is urgent. With Minnesota's population projected to grow by 1 million people during the next 20 years, DNR biologists and county planners are anticipating more housing development along lakeshores. Unless native vegetation is protected, water quality and fishing opportunities in Minnesota lakes will be significantly degraded.
The Intra-Lake Land Use Reclassification Pilot Program is the first comprehensive, science-based inventory of shorelines -- from offshore plants to upland wildlife -- conducted in the state for habitat protection. The data collected in the inventory will be helpful in protecting environmentally sensitive areas in and around lakes, says John Sumption, director of the Cass County Environmental Services Department. The project is a collaboration between the DNR, Cass County, and the Leech Lake Band of Ojibwe.
"We've been under a lot of pressure as new developments have been proposed,'' says Sumption of Leech Lake and other Cass County lakes. "It became clear we need a set of objective criteria to protect sensitive shoreland areas."
For the past four years, the Intra-Lake program has inventoried aquatic vegetation, habitat, fish, and wildlife along the shores of Leech Lake and several other lakes to assess the sensitivity of shorelands to development.
"It's not only aquatic plants, but the presence of wetlands and hydric soils, animal use in the area, and the presence of rare and endangered species,'' says Paul Radomski, the DNR senior fisheries research biologist heading the project. "We're bringing new and existing information together. It's a look at the big picture."
Sumption says the data from the aquatic plant, shoreline, and upland inventory will provide the scientific basis for new Cass County zoning ordinances. For sensitive areas needing protection, that might mean requiring bigger lot sizes -- increased from the current minimum of 30,000 square feet to 80,000 square feet -- and greater setbacks for homes from shorelines. It might also mean implementing new rules for developing shoreland, such as allowing a subdivision to include only one dock on a shoreline rather than several. Fewer docks -- which means a reduced footprint from human activity in critical near-shore areas -- would give greater protection to shallow pondweeds and algae where muskies spawn, Sumption says.
To protect plants, people first must know where they are. And data about the plant beds in Leech Lake has been sparse, until now. The last survey of Leech Lake's aquatic plants was conducted in 1924, and its data was sketchy.
"It was all we had,'' says Donna Perleberg, DNR aquatic plant ecologist. "It is a few paragraphs that give you a nice description that, yes, there are aquatic plants in shallow bays."
So Perleberg devised the state's first aquatic plant survey of Leech Lake -- a significant undertaking because Minnesota's third largest lake is 114,000 acres with 195 miles of shoreline. A survey using scuba gear would have been impractical -- too expensive and time consuming, Perleberg says. Instead, she divided the lake into sections and enlisted the help of other biologists from the DNR and the Leech Lake band, student interns, and several volunteers from the Leech Lake Association.
Using global position system units and a modified garden rake, two- and three-person teams set out to sample lake-bottom plants during four summers. Every 200 meters, basin by basin, survey crews recorded water depth. They tossed the rake head into the water, dragged it back to the boat with a rope, and then identified the plants on the rake. They marked plant locations on the lake map. The crews took 9,800 samples around the lake, but not all samples brought up plants. About 61 percent of the lake has naturally low populations of plants or none at all.
"Leech Lake actually contains a healthy plant community," Perleberg says. "It's very diverse."
Not only is there abundant chara -- the algae that serve as critical muskie spawning habitat -- but there are also 25 other submerged plant species, including 11 species of pondweeds. Submerged plants host the aquatic invertebrates such as caddisfly and dragonfly larvae that form the foundation of the lake's ecological food web. Clasping-leaf pondweed is the most common species, but Leech Lake also has beds of flat-stem pondweed, large-leaf pondweed, and whitestem pondweed. Perleberg discovered that what anglers often call "cabbage," a favorite muskie haunt, was actually any number of pondweeds.
The crews also cataloged wild celery, wild rice, coontail, and northern milfoil. These submerged plants grew as deep as 24 feet but were most common in less than 10 feet.
Unfortunately, the survey could not solve the mystery of what happened to Al Maas' favorite muskie "weedbeds" because it could only look at what plants exist today. And the crews only sampled plants every 200 meters.
"With small site changes, we're out of luck," Perleberg says. "It's a huge lake, and your favorite fishing bed might occur between our 200-meter data point."
"The survey gives us our first comprehensive, scientifically repeatable survey of Leech Lake vegetation," says Pat Rivers, a DNR assistant area fisheries supervisor. "It gives us a baseline to start larger comparisons for the future."
The Intra-Lake pilot project is now surveying Ten Mile, Birch, Washburn, Sand, and Woman lakes. Radomski hopes the DNR will conduct similar surveys of Cass County's 17 largest lakes. The hope is that scientific surveys can help prevent the loss of aquatic plants and detect losses early enough to avert further harm.
"All these weedbeds are important to us fishermen,'' Maas says. "We have to stay on top of it. We have 114,000 acres that are too valuable to screw up."