|(c)Engbretson Underwater Photography|
(This article appeared in the Iron Mountain Daily News Saturday-Sunday July 26-27 2014, and in the Florence Mining News Wild Rivers Guide Summer 2014. It details how the application of chemical herbicides to treat Eurasian Watermilfoil led to unexpected consequences for one Wisconsin Lake.)
Imagine a town consisting entirely of seniors. The town has no children, no teenagers, and no young adults. All the schools, playgrounds, and sports fields have closed. The town is eerily empty and still. And every year, as seniors pass on, the town’s population grows smaller and smaller. With no young people to replace the departed, the town will simply disappear from the map. A grim future indeed.
Until last year, this same sad demise seemed destined for Lake Ellwood in Florence County, WI. In its waters, bluegill and largemouth bass had grown old. For the better part of a decade, no young fish were surviving to replace them. But now it seems that a corner has been turned and the news is good. Today, Ellwood is a lake on the brink of recovery. The story of the lake’s resurrection is a tale that involves invasive plants, a dedicated fisheries biologist, and a host of scientists working against the clock to save a small but beloved piece of Florence County.
A healthy lake gets a steady stream of newborn fish every year, and the newborns that survive to maturity constantly enlarge the adult population. Fish biologists call this process recruitment. Of all native fish, largemouth bass and bluegill are both extremely prolific and they have shown outstanding talent for recruitment. Unlike walleyes, which require very specific conditions to reproduce, largemouth bass and bluegills thrive even when conditions are far less than ideal. Typically, when two years pass without largemouth bass and bluegill recruitment, fish managers become concerned, and Lake Ellwood has now seen seven consecutive years with failed recruitment. Dr. Andrew Rypel is the state’s lead panfish researcher for the Wisconsin Department of Natural Resources. “It’s an eyebrow-raiser to be sure. What’s happened on Lake Ellwood has gotten our attention. It’s very weird.”
Greg Matzke is the DNR’s senior fish biologist for Florence and Forest Counties. When I visited him in his office at the Florence Resources Center a year ago, he was eager to discuss Lake Ellwood. “The fisheries biologist position for Florence was vacant for three years prior to my arrival,” he told me. “By the time I got here in year 2010, many of our lakes hadn’t been surveyed in a while. When we got around to looking at Lake Ellwood in 2012, the fish population hadn’t been surveyed for a decade. What we found was a lake with few young fish. By the end of our spring survey it was clear to me that something was wrong with some of the major fish populations in Lake Ellwood.” What Matzke documented in 2012 was an almost total collapse of the fish community. In Wisconsin, a failure of this magnitude in largemouth bass and bluegill recruitment is utterly unprecedented.
Matzke typed excitedly on his keyboard as a graph flashed onto the screen. Compiled from the data he had collected, the graph showed a sudden drop in northern pike recruitment after 2004, followed by bluegill and largemouth bass recruitment failures after 2006. Northern pike and largemouth bass recruitment had not occurred at all since 2004 and 2008 respectively, while bluegill recruitment fell off and became insignificant after 2006. “We surveyed that lake extensively, with 44 fyke net lifts and 7 complete electrofishing surveys totaling 20.22 miles (on a lake with 2.8 miles of shoreline) and couldn’t find a single fish younger than five, six and eight years of age, for largemouth, black crappie and northern pike. Not one.” said Matzke. “Nobody has ever seen anything like it.” In total Matzke spent 19 days surveying the fishery in one small lake, which is a great deal of time and effort, and I wondered how many lakes earn such scrutiny. “Not many,” said Matzke. I asked the big question: “What happened to the fish?” He paused and exhaled. In a reflective mood, he lowered his voice: “At first I had no idea, but after gathering and analyzing all the data it’s quite clear…. I believe it has to do with the milfoil treatments out there.”
THE MILFOIL CONNECTION
In the bars of Spread Eagle, fishing is a hot topic among the locals. It fills the air in the summer months, when local businesses are booming and lakefront owners are spending more time on the water. Between rounds, someone mentions the fish crash in Lake Ellwood, and explanations flow like beer from a freshly-tapped keg. On a steamy night last July at the Chuck Wagon Restaurant, the fate of the lake engaged almost every person in the room. Barroom biologists blamed culprits ranging from low water levels to fish cribs and even invasive Eurasian watermilfoil (EWM) sucking the oxygen out of the lake.
Back in their offices, Matzke and his colleagues considered these possibilities and decided none of them were credible because these same conditions exist on hundreds of lakes throughout Northern Wisconsin, and none of the lakes has shown collapses in fish as was documented in Lake Ellwood. In their opinion, the crash stemmed from chemical herbicides applied to control the invasive plant Eurasian watermilfoil.
Eurasian watermilfoil (EWM) was discovered in Lake Ellwood in 2002. Treatments started during the next spring. The Lake Ellwood Association contracted with a lake management firm to monitor and treat the lake every spring thereafter with very good success. As chemical treatments continued, invasive plants began to subside. Encouraged by their success, the lake association continued treatments in the hope of eradicating small but persistent areas that would materialize. An unintended consequence was that native plants were also being killed by the herbicide.
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