Ironies shown in Lake Mallalieu management-plan research
Researchers outlined several ironies about Lake Mallalieu’s plant density, water quality and fish populations at an informational meeting on the lake’s new management plan last week.
--The feared invasive plant, Eurasian water milfoil, and white water lily were by far the lake’s most dominant vegetation during a survey last year. But that was actually a good thing, since few noninvasive plant species remain to provide fish habitat and food for other organisms, and to help keep the water clean.
“Eurasian water milfoil is an invasive plant, but it’s not acting invasive at this time,” said state Department of Natural Resources water-quality specialist Patrick “Buzz” Sorge after a report by fellow specialist Jody Lepsch May 19.
“It is habitat. It is providing some structure, and other plants aren’t there.”
Lepsch had reported that only 29 percent of Lake Mallalieu supported aquatic vegetation in 2013 -- mostly near the shorelines -- compared to 80 percent in healthy Wisconsin lakes. About 62 percent of Lake Mallalieu’s vegetation area was home to white water lily, while about 20 percent contained Eurasian water milfoil.
Another irony at last week’s meeting, which was organized by the Lake Mallalieu Association after four years of work on the management plan with St. Croix County and DNR experts:
--A 1998 lake drawdown improved water quality, but a follow-up in 2005 apparently contributed to the vegetation and fish-habitat problem by harming noninvasive plant species amid continued phosphorus runoff.
“So drawdowns are not really an option” for management in the near future, Lepsch said.
She added: “Your water quality problems are coming from phosphorus,” largely from agriculture near the watershed north of Lake Mallalieu.
A 20-30 percent reduction in phosphorus runoff will be needed to bring the lake’s water quality under control, Lepsch said.
Lake Mallalieu Association vice president Doug Meyers emphasized in an interview after the meeting that “no one is pointing any fingers” regarding the phosphorus problem, and he noted that county officials are working with local farmers on a balanced solution.
“There are no bad guys here. We all are good guys,” Meyers said. “The association is more trying to educate lake owners on how to do their part.”
Still another irony from the informational meeting:
--The lake’s 2013 largemouth bass and pan fish densities were down from 2001, and pike fish populations continued to be low -- invasive rusty crayfish, the declining plant community and past drawdowns amid phosphorus runoff were cited among likely culprits. But Lake Mallalieu fishing is still among the best in the state, said DNR fisheries biologist Marty Engel.
“Lake Mallalieu is known for outstanding bass fishing in trophy proportions,” he noted in his report, which ranked the lake’s smallmouth-bass population in Wisconsin’s 92nd percentile and its largemouth-bass population in the 66th percentile.
He added that in the absence of healthy aquatic-plant diversity and density, fallen trees, for example, can provide longstanding alternative habitat for many fish species, including pike.
However, most shoreline residents are discouraged from allowing fallen or cut-down trees to remain in the water near their properties, Engel said.
More than 60 people attended the May 19 meeting at the Hudson House Grand Hotel, and while the discussion on 2013 surveys and other research occasionally grew a little testy, many eyes appeared to have been opened.
Given the complexity of the lake’s problems and the variety of circumstances around its 289 acres, “balance” was a frequent watchword at the meeting where future management is concerned.
“We all tend to think the conditions near our own places are typical of Lake Mallalieu, but it’s really like 50 different lakes,” said one man, for example.
Immediately after, Sorge added of the experts’ and association’s research and management efforts to date: “The beauty of this kind of information is that instead of venturing a guess … we can say, ‘This is how the lake has changed.’”
Meyers listed lake-property chemical runoff control, shoreline protection and erosion reduction among management steps that association member will be asked to consider as the new management plan moves forward.
Lake Mallalieu was designated by the U.S. Environmental Protection as an impaired body of water in 2004, which allowed the DNR to work with St. Croix County to work on runoff and other problems using Total Maximum Daily Load funding.
TMDL funding for the new management plan was approved in 2010.
The association, which has formally adopted the plan, was founded in the early 1980s and got its first DNR planning grant in 1991.
Other grants followed in 1998, and a previous lake-management plan was published in 2001.