With the summer boating season officially underway, invasive species check stations in Montana have already intercepted three mussel-contaminated watercraft traveling through the state.

In a Monday press release, officials from the Blackfeet Nation stated that a boat headed for the Flathead Valley was stopped May 21 by inspectors at the reservation’s watercraft inspection station in Seville, and was found to have remnants of mussels attached.

The interception of the boat, which was owned by a Montanan but traveling from mussel-infested waters in Michigan, was in addition to a pair of mussel-encrusted boats that were stopped at check stations over the Memorial Day weekend. One of those boats was also destined in-state, while the second was en route to British Columbia.

The boat owner took the boat to a car wash to dislodge the mussels on the boat prior to entering the Blackfeet Reservation, but did not take the boat for a professional decontamination,” the release notes, adding that inspectors detected byssal threads from mussels near an intake on the vessel.

“Native mussels do not have byssal threads — the invasive mussels use their byssal thread to attach to boats and hitch a ride to mussel-free water bodies,” the release added.

The boat was decontaminated by the Whitefish Lake Institute, which confirmed the byssal threads and also detected a zebra mussel shell in on of the compartments.

The owners agreed to not launch the vessel for a month to ensure the boat would pose no risk to local waters, the release stated.

Caryn Miske, executive director for the Flathead Basin Commission pointed to the detections as evidence that boaters need to up their vigilance in ensuring that their watercraft are properly decontaminated and free of aquatic invasive species. The commission has partnered with the Blackfeet Nation since 2015 to bolster the region’s invasive-species prevention efforts.

“Kudos to the inspectors for their diligence,” Miske stated in the release. “We in the Flathead are very fortunate to have the Blackfeet protecting our northeastern flank, since this is not the first mussel-fouled boat bound for the Flathead that the tribe has intercepted.”

Invasive mussel larvae — either quagga or zebra — were confirmed to be present in Montana waters for the first time last fall, after water samples taken from Tiber Reservoir over the summer tested positive for the invasive species. In response, the state passed legislation earlier this year to more than double the number of check stations in the state and strengthen regulations for boaters traveling from out-of-state or crossing the Continental Divide into the Columbia River Basin.