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Wyoming Battles Invasive Species on Trailered Boats

Cheyenne – Wyoming remains free of invasive mussels after a challenging year protecting the state from aquatic invasive species.

Over the summer season, Wyoming Game and Fish Department watercraft checkstations inspected more than 68,000 boats across the state to protect Wyoming’s waters from invasive aquatic plants and animals. Game and Fish personnel decontaminated 924 boats, and inspectors found live mussels on two. It’s the highest number of decontaminations ever since the AIS program was established in 2010 by the State Legislature and the first time live mussels were found on boats at Wyoming’s checkstations.

“Checkstations were extremely busy in 2020, and we stayed that way in 2021,” said Josh Leonard, Game and Fish AIS coordinator. “It was another record-breaking year, but this time it was because we intercepted more risk.”

AIS checkstations are regarded as the first line of defense against invasives entering the state or being spread between Wyoming’s waters. Those range from invasive plants like curly pondweed, which Wyoming does have, to species that the state has managed to keep out, like Asian carp and zebra or quagga mussels.

In Wyoming the law requires any watercraft transported into the state from March 1 through Nov. 30 must undergo a mandatory inspection by an authorized inspector prior to launching. Any watercraft that has been in a water infested with zebra/quagga mussels within the last 30 days is required to undergo a mandatory inspection by an authorized inspector prior to launching during all months of the year. All watercraft must stop at any open watercraft check station on their route of travel, even if not intending to launch in Wyoming.

As more states and waters turn up with AIS, particularly mussels, the threat to Wyoming continues to swell. Decontaminations in 2021 were more than double the 480 conducted in 2019. In 2021, checkstation inspectors found mussels on 54 boats; in 2019 only 19 boats were intercepted with mussels.

While there’s a growing threat of AIS, Leonard said more public awareness of AIS in general led to increased compliance to stop at required watercraft checkstations, and ultimately the record-breaking numbers. Leonard attributes that partially to a partnership with Wyoming Department of Transportation to use highway signage reminding boaters to stop at checkstations — flashing ALL BOATERS MUST STOP for most of the summer months.

The other reason he suspects more adherence to the rules is due to the unfortunate identification of zebra mussels in moss balls, a popular aquarium plant, in pet stores this last spring. That discovery thrust AIS into the spotlight.

Game and Fish and the Wyoming Department of Agriculture led a Governor’s response team to remove moss balls from retail shelves, monitor municipal water treatment plants for traces of zebra mussel DNA and get the word out to Wyomingites to watch for AIS in their homes. Through a robust communications campaign, residents were encouraged to dispose of any moss balls they owned by boiling the plants and the tank water, and then pouring it outside on grass or soil.

“The outreach around moss balls and zebra mussels created a lot more awareness about the threat of AIS to our state,” Leonard said.

Invasive mussels are one of the most destructive forms of AIS and it is very unlikely to eradicate mussels once they are established in natural water. While the state was the most vulnerable it’s ever been to a mussel infestation, Wyoming remains free of zebra and quagga mussels. Game and Fish monitors for mussels and other invasives by sampling 20 waters twice per year and an additional 50 waters once per year. This year, municipal water testing was also added to that list to make sure mussels didn’t find their way into pipes from aquariums. The department also finalized rapid response plans in 2021 to quickly respond if mussels are ever found in the state’s 23 most vulnerable natural waters.

“There’s still a place in the United States that doesn’t have mussels — it’s Wyoming — and we’re doing all we can to keep it that way, with inspectors working very hard to keep AIS out.” Leonard said. “Wyoming has wonderful, diverse water resources, and we need to protect them.”


(Sara DiRienzo, Public Information Officer – (

– WGFD –

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