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Invasive zebra mussels found in South Dakota reservoir 27 miles from Wyoming border


CASPER, Wyo. — Zebra mussels, an invasive aquatic species, were discovered in Pactola Reservoir west of Rapid City, South Dakota, last week and the Wyoming Game and Fish Department said Thursday that the finding is cause for concern in Wyoming.

Pactola Reservoir is 27 miles from the Wyoming border and is a popular destination for both Wyoming and South Dakota residents, Game and Fish said. Wyoming is one of the few states where invasive zebra and quagga mussels have yet to be discovered. If the species get into Wyoming waters, it could mean destructive consequences for Wyoming’s native species and habitat, according to Game and Fish.

Mussels can easily be spread, including in their microscopic state, from even small amounts of water left standing in a boat, Game and Fish said.

“Many boaters from South Dakota pop over to Wyoming for the day and vice-versa,” Josh Leonard, aquatic invasive species coordinator with Game and Fish, said. “The risk mussels could spread is the highest it’s ever been.”

Boaters must stop at aquatic invasive species check stations in Wyoming under state law. They must stop even if they’ve previously stopped at another station.

“We’re confronting this threat head-on,” Leonard said. “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 check stations to keep Wyoming — and the waters they like to visit — safe.” 

If invasive species are detected or if their presence is suspected to be possible on a boat, Game and Fish will decontaminate it at check stations and educate people on how to reduce the likelihood of spreading invasive species.

In addition to stopping at check stations, boats transported into Wyoming between March 1 and Nov. 30 must undergo an inspection by an authorized inspector prior to launching on any waterway in the state. Game and Fish provides a list of inspection locations 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,” the department said. “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 said it will closely monitor impacts of zebra mussels in Pactola Reservoir and may make adjustments to boating requirements if necessary to help prevent the introduction of mussels to Wyoming.

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