A dead invasive quagga mussel was found on the shoreline of Prineville Reservoir in Central Oregon in early June. This is the first time the thumbnail-sized, freshwater mussel has been spotted near a body of water in Oregon.

“We are taking this finding extremely seriously, but also cautiously as we work to confirm what we’re seeing at Prineville Reservoir,” Keith DeHart, the aquatic invasive species coordinator for the Oregon Department of Fish and Wildlife, said in a statement. “We are coordinating closely with our state, federal, tribal, and local partners, and preparing to move quickly based on the evidence we find.”

Quagga mussels can reproduce extremely quickly, posing both an economic and environmental threat. They can attach to any hard surface, such as boats or hydroelectric infrastructure, clog up irrigation systems that farmers depend on and disrupt aquatic ecosystems by outcompeting other native mussel species and fish.

But crews with Portland State University’s Center for Lakes and Reservoirs only found the one single adult quagga mussel during their routine invasive species survey on June 6. The Oregon Department of Fish and Wildlife does not know how the mussel ended up on the shore of the reservoir

So far, crews have not found any more mussels on Prineville Reservoir shorelines. And test results from water samples have shown no signs of invasive mussel larvae.

The quagga mussel came from Eastern Europe to the Great Lakes in the 1980s. It’s about an inch long when it reaches adulthood and triangular in shape with brown and tan stripes on its shell.

Over the last few years, quagga mussels have been found across the country, including in California, Nevada and Utah. The Pacific Northwest has been largely spared, though in 2023, the mussel was discovered in Idaho along the Snake River by Twin Falls. Environmental state agencies there have spent millions of dollars to fight the invasive species.

Monitoring crews will continue routine sampling efforts to ensure early detection and subsequent rapid response if quagga mussels are present in the Prineville Reservoir, according to ODFW. The agency will increase monitoring at watercraft inspection stations for boats entering Oregon, which is already required. This includes boats, canoes, kayaks and even paddleboards.

A roving check station will also periodically be at boat ramps around Prineville Reservoir and Central Oregon to inspect watercraft for invasive species.

“Continued vigilance and cooperation from the public are vital to protecting Oregon’s waters and keeping recreation areas open,” DeHart said.

There are no plans to close Prineville Reservoir for now.

Because recreational boats are one of the primary sources of freshwater invasive mussel spread in the U.S., ODFW officials are recommending boaters clean their boat, drain it and allow it to dry before launching it into a new lake or river.

People can report any suspicious mussel sightings to the Oregon Invasive Species Hotline at 1‑866‑INVADER or online at the invasive species hotline website.

News Source : https://www.opb.org/article/2026/06/24/invasive-quagga-mussel-found-on-central-oregon-reservoir-shoreline/