Game and Fish concerned about zebra mussel discovery in South Dakota

Pactola Reservoir nearest water to WY with invasive mussels

7/21/2022 8:22:12 PM

Cheyenne - The threat of zebra and quagga mussels to Wyoming’s waters is closer than ever before. Last week zebra mussels were discovered in Pactola Reservoir, located 13 miles west of Rapid City, South Dakota, in the Black Hills. The reservoir is only 27 miles from the Wyoming border and is a popular boating destination for Wyoming and South Dakota residents. 

The westward expansion of invasive mussels is significant as Wyoming remains one of the few states yet to have the destructive species. The Wyoming Game and Fish Department is concerned about the potential impacts the nearby zebra mussels could have on Wyoming, especially the inadvertent movement of invasive mussels into the state.

“We’re confronting this threat head-on. said Josh Leonard, Game and Fish AIS coordinator. “Game and Fish is increasing our diligence to inspect watercraft for mussels and other AIS in northeast Wyoming. We urge boaters to take extra time to practice good Clean, Drain, Dry protocols and stop at checkstations to keep Wyoming — and the waters they like to visit — safe.” 

This is the first time zebra mussels have been found in a natural water body this close to Wyoming’s border. The discovery is especially concerning as many boaters frequent waters on both sides of the state line.

“Many boaters from South Dakota pop over to Wyoming for the day and vice-versa,” Leonard said. “The risk mussels could spread is the highest it's ever been.”

Mussels can spread easily, even in their microscopic state, from just a little water left standing on a boat.  If AIS — or the possibility —  is found on watercraft, Game and Fish will decontaminate the boat and educate boaters on how to reduce transmission of these threats themselves to make the next inspection quicker. 

It’s state law that all boaters must stop when coming upon an AIS inspection station — even if they stopped at one prior. Any watercraft transported into Wyoming from March 1-Nov. 30 must undergo a mandatory inspection by an authorized inspector prior to launching on any Wyoming waterway. A list of inspection locations is available online.

If boaters entering Wyoming do not encounter an open AIS check station on their route of travel, it is the boater’s responsibility to seek out an inspection. Further, if the watercraft was used on a water suspect or positive for invasive mussels in the last 30 days, it must be inspected prior to launching year-round and may require decontamination. Full rules are available online. 

Game and Fish will be closely monitoring the impacts of zebra mussels in Pactola Reservoir and make adjustments to Wyoming’s boater requirements, if needed, to stave off mussels.

“The threat is real — and it is here. It’s our top priority to keep mussels out of Wyoming — for our natural resources, recreation and livelihoods,” Leonard said. “We need your help so please help us protect our state by stopping at our watercraft checkstations.”

(Sara DiRienzo, Public Information Officer - (

- WGFD -

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