CASPER, Wyo. — A watercraft harboring live, invasive zebra mussels was intercepted on Sept. 22 at the northeast Wyoming border by the Wyoming Game and Fish Department, the agency announced on Wednesday.
The watercraft had been moored for several months in South Dakota’s Pactola Reservoir, where a population of mussels was discovered in 2022. This was the first watercraft with verified live mussels discovered at a Wyoming check station this year, Game and Fish said.
The highly invasive zebra and quagga mussels can wreak havoc in freshwater ecosystems and can clog dam systems, municipal water pipes, irrigation systems and treatment facilities. “An infestation in just one of Wyoming’s water treatment facilities could cost hundreds of thousands of dollars annually to remove mussels, keep water flowing and mitigate damage — costs that could be passed on to all water users,” Game and Fish said.
Live adult mussels can start reproducing the moment they hit the water if the conditions are right, so a watercraft harboring these animals could easily start a new population, WGFD said. Wyoming remains one of only five states in the continental United States that are mussel-free, with every state bordering Wyoming, except Montana, having at least one waterbody containing mussels.
State law says that anyone with a watercraft, including a kayak or canoe, must stop when coming upon an open aquatic invasive species inspection station — even if they stopped at one prior or do not intend to launch in Wyoming.
Game and Fish said the owner of the incoming watercraft was stopped at the Beulah check station when the mussels were discovered. Inspectors removed live zebra mussels in multiple water intakes, along the pontoon and in other areas of the inspected boat.
“The findings of the mussel-fouled watercraft is a stark example of the importance of watercraft inspections,” Game and Fish said. “Prior to the program’s expansion, inspection stations in Wyoming would have been closed for the season at this point in the year, and the boat may have gone unnoticed.”
Any watercraft transported into Wyoming from March 1 to Nov. 30 must undergo a mandatory inspection by an authorized inspector prior to launching on any Wyoming waterway.
Watercraft inspectors statewide have inspected over 73,000 boats and conducted 1,121 decontaminations this year. They also intercepted 43 other boats containing non-viable invasive mussels.
