Five years later, zebra mussels' impact on Green Lake becoming clear
Water clarity harms walleye numbers, but recreation and economic activity remain robust
SPICER — It was July 21, 2014, when a property owner on the southeast corner of Green Lake found a single, adult zebra mussel on the post of his dock in four feet of water.
It was the first ever found in the lake.
One year later: “There are billions of them,” Mike Schoffman, of Mike’s Dock and Yard in Spicer, told the West Central Tribune as he removed docks from the lake in October 2015. “They are in every nook and cranny.”
That remains the case five years later too. We are only now learning what the arrival of this aquatic invasive species means for Kandiyohi County’s most popular recreational lake.
We can say this much for certain: Their arrival is bad news for the lake’s walleye and perch populations. Zebra mussels are accelerating changes in the lake that are reducing walleye numbers. The number of walleyes caught in gill nets by the Spicer-based fisheries crew with the Minnesota Department of Natural Resources has been declining for years, and walleye fell to their lowest numbers ever, according to Dave Coahran, fisheries supervisor.
On the other hand, the economic and recreational impacts have not been as great as once feared.
Originally, there were fears that zebra mussels would lower property values and fill beaches with drifts of razor sharp shells.
Neither of these scenarios has played out. “I don’t see it,” said Jane Vikse, of Vikse Real Estate of Spicer, when asked if zebra mussels have adversely affected property values along the lake.
Property values on the lake have risen in the last five years, and real estate sales have remained strong. “We haven’t seen any decline in sales,” said Sue Blumhoefer, West Central Association of Realtors.
She pointed to recent sales data showing that the median price of housing in the Spicer market has risen by 10 percent in the last year.
Val Skor, Kandiyohi County Assessor, confirmed that sales have been strong. There have been no downward market changes since the discovery of zebra mussels, she said. There are typically anywhere from eight to 20 sales around Green Lake each year.
Dean and Laura Anfinson have been managing Green Lake County Park on the lake’s north shore since well before the arrival of zebra mussels. When asked if zebra mussels have affected recreational activities at the popular campground, Dean Anfinson said, “not really.”
More kids are wearing water shoes when swimming these days, but that is about the only apparent change, according to Anfinson. Boat traffic, fishing, swimming and camping all continue at levels no different than before the arrival of zebra mussels.
“A moderate nuisance” is how Scott Carlson, president of the Green Lake Property Owners Association, described the impact of zebra mussels on activities associated with recreation in the lake.
All the same, the association remains as committed as ever to managing aquatic invasive species and educating people about them. The association continues to help fund research into controlling invasive species and their spread.
It's all for good reason too. Zebra mussels remain prevalent in the lake and are here to stay. It’s too early to know how abundant their numbers will remain in the lake, but their numbers can only be described as significant.
Gary Montz, an aquatic invertebrate scientist with the Minnesota Department of Natural Resources, has been conducting zebra mussel counts on the lake since 2016. He plans to continue to do so for another couple of years at least to get a better understanding of how they will fare in the lake.
Montz said there was the initial, big “pulse” in numbers when the newly introduced invasive species took hold in the lake. There was another big jump in smaller or younger zebra mussels in 2017. Last year, those numbers fell back to numbers closer to those of 2016, but they are still abundant.
Last year’s drop may be a sign that the population is stabilizing, said Montz, adding that it could also just reflect natural fluctuations that will continue for years to come. Three years of data do not provide enough information to make any predictions, he cautioned.
He is sampling zebra mussels at more than 50 locations in the lake, and expects to conduct this year’s count in a week or two. Zebra mussels are present at the test sites in significant numbers throughout the lake, with the exception of a few deeper locations with soft bottoms and no vegetation, he said.
They’re attached to aquatic plants and cover rocks and harder substrate throughout the lake, or wherever suitable habitat is found. “Which is a fair amount of Green Lake, at least from what we can tell from our samples,” Montz said.
In hopes of delaying the arrival of zebra mussels to Green Lake, Kandiyohi County had made itself a leader in working to prevent the spread of aquatic invasive species years before their arrival. The county remains committed to slowing their spread, but strategies are shifting.
The county is using a larger share of the $251,039 in state funds it received this year for public education work, and has reduced the number of inspections being conducted at water access sites.
The county is working to increase the use of its decontamination units by boaters, and is moving the two units around to different lakes this year, according to Russ Hilbert, county aquatic invasive species coordinator.
The Green Lake Property Owners Association was an early advocate for public education and efforts to slow the spread of aquatic invasive species. Along with funding research and control efforts for zebra mussels, the lake association also invests in herbicide treatments to keep Eurasian watermilfoil in check in the lake.
Association President Carlson said it’s true that zebra mussels are not the subject of worry that they once were. Instead, there is a greater worry in their place. The discovery of the invasive starry stonewort in Lake Koronis poses a very serious threat to Green and other lakes, he said.
Thick mats of the algae have the potential of disrupting boating and replacing native vegetation with monoculture patches of the algae. “It could make the other two (zebra mussels and Eurasian watermilfoil) look like child’s play,” Carlson said.