Laura Butterbrodt

The Watertown Public Opinion

July 19, 2020

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South Dakota Game, Fish and Parks’ July 10 announcement of the zebra mussel infestation in Day County’s Pickerel Lake has sounded the alarm for many people in the Glacial Lakes region.

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“It’s one of those things you just hope is not going to arrive at your doorstep, but it did,” said Dave Pearson, president of the Pickerel Lake Conservancy. “My initial reaction was I was angry and concerned. Zebra mussels are a very troublesome species. There’s no known program for eradicating or managing them effectively in a freshwater lake, so once they get established, they’re very difficult to control.”

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Pickerel is the first lake in northeast South Dakota in which the invasive species has been found. GFP Fisheries Supervisor Mark Ermer said one of the mussels was already an inch and a half in size, which indicates it has been growing there for at least two years already.

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Ermer said GFP staff immediately set out to search other area lakes, including Waubay, Kampeska, Pelican, Poinsett, Roy, Bitter, Enemy Swim and Clear. So far no other mussels have been found.

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“We did make a pretty concerted effort to go around to all of our boat ramps at our very high-use lakes and take another good look like we did at Pickerel,” Ermer said. “We had to look pretty hard at Pickerel to find them, so we did that same type of search at these other lakes to see if we had them and we didn’t know yet. So far we haven’t come up with one… Doesn’t mean they’re not there.”

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The problem with containing zebra mussels is they reproduce through microscopic larvae called veligers, which can survive in standing water or flow downstream into other bodies of water before settling on a surface to grow.

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Pickerel Lake is the headwaters of a chain of lakes called the Waubay Lakes Basin. Waubay Lake is next in the line of drainage, which means it is very likely veligers have already drifted downstream into the lake. However, GFP has not found any mussels.

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“It’s common practice for us, when we have a lake that’s infested and it flows directly into the next downstream lake — we’re probably going to identify Waubay Lake as a likely infested lake,” Ermer said.

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The South Dakota Game, Fish and Parks Commission has scheduled an emergency meeting July 27 to determine which lakes in the chain will be put on the list of likely infested lakes, and also to determine what kind of containment and treatment should be considered.

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For now, the following regulations will be put in place for Pickerel Lake:

• All boats departing Pickerel Lake will be required to be cleaned and drained.

• Boats remaining on the lake for three or more days will need to be decontaminated before the boat can be launched on any South Dakota body of water. Decontamination can be accomplished using a 140-plus degree power washer or keeping the boat out of the water for at least five days.

• Wake boats with ballast tanks containing at least one gallon of residual water will need to have the tanks decontaminated along with the rest of the boat.

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The regulations will be put in place once GFP finishes the process of formally designating Pickerel Lake as an invasive species-contaminated water.

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Clean, Drain, Dry

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It’s almost certain that Pickerel Lake became infested because of boaters who didn’t properly clean their boat and equipment after visiting a lake with zebra mussels, then unknowingly introduced veligers into Pickerel Lake.

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Ermer said GFP has been working for years now to educate the public with the Clean, Drain, Dry campaign. Boaters should walk around the boat on the trailer to look for any vegetation, mud or growths. All drains must be removed and motors must be put into a vertical position to drain. Finally, any remaining standing water in the boat needs to be soaked up with a towel or sponge.

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“It’s more of us training all boaters to have a different way of doing things. It’s almost like a common practice that we’ve got to get them used to doing,” he said. “If everybody does that, we will be much more successful in containing these things where they’re at and not seeing new infestations happen.”

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Pearson said the Pickerel Lake Conservancy had worked with GFP for years to increase signage at boat launches, as well as educating members about the dangers of invasive species to the lake. Because of those efforts, the discovery of the zebra mussels came as a surprise to him.

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“We hoped that people would take those warnings seriously and be responsible for how they transport their boats from one place to another,” Pearson said.

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He said he believes most boaters know about the Clean, Drain, Dry practice, but they don’t all actually do it.

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Ermer said GFP has transitioned from an educational approach of enforcing Clean, Drain, Dry to a more aggressive enforcement by issuing tickets and having more employees working full time to inspect boats on roads and at boat launches. There are mandatory inspection stations throughout the region that all vehicles pulling boats must stop at, and if law enforcement officers see a boat on a roadway with a plug intact, they can pull the driver over and issue a ticket.

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“I think that South Dakota is doing better, but there’s a lot more that could be done,” Pearson said. “And part of the problem is money to staff the state parks and put more people there to inspect boats and that sort of thing.”

 

Effects on lakes

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Pearson said the conservancy is reaching out to other lake associations that are dealing with zebra mussels to learn about their approaches and what they have learned so far.

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One conservancy member, Dan Loveland, shared photos of a boat lift covered in zebra mussels at Green Lake near Spicer, Minn.

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“No doubt this will eventually be in our future as well,” he wrote in an email. “There has been an email circulation around the lake suggesting that perhaps zebra mussels might not easily attach to aluminum structures. Doesn’t seem to be the case. We should assume that they can and will attach to just about any hard surface as the population proliferates.”

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This is true — and is the cause of many of the negative effects the mussels have on bodies of water. According to the Minnesota Department of Natural Resources, zebra mussels reduce boat efficiency by encrusting motors and hulls, which is costly to clean and repair. They also clog water intakes.

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Their sharp shells can cut the feet of swimmers and pets when attached to rocks, docks, rafts or ladders.

And they set an imbalance to the water’s natural ecosystem. They filter the water, which might make lakes look clearer, but it removes particles that aquatic creatures need for food. The clarity of the water can also increase the growth of aquatic plants.

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Zebra mussels are in other South Dakota bodies of water, including the Missouri River reservoirs Lewis and Clark Lake near Yankton and Lake Sharp near Pierre. They have been found in all of the Great Lakes since 1990.

There is currently no known way to safely remove zebra mussels from a lake or river without damaging the rest of the aquatic ecosystem.

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Zebra mussels can grow up to 2 inches in size and live for four to five years. According to the U.S. Fish and Wildlife Service, female zebra mussels can lay more than 40,000 eggs in a reproductive cycle and up to 1 million in a spawning season. The larvae emerge within three to five days after the eggs are fertilized and are free-swimming for up to a month.

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“The easy part that people can remember coming out of this is if they can just change their practices when they leave a lake — when they think of this stuff and try to follow that Clean, Drain, Dry — then we’ve eliminated a lot of the possibilities and the vectors for these things to get moved around,” Ermer said.

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