EDITOR’S NOTE: Why are we sharing information about invasive mussels in Prineville reservoir? As the “land of many waters”, it’s important to protect our waterways, and during the summer, boaters are traveling throughout Oregon enjoying are many waterway opportunities. Let’s keep invasive mussels and other invasive species – Clean, Drain and Dry your vessels.
(PRINEVILLE, OR) – A single dead adult quagga mussel was found out of water on the shoreline at Prineville Reservoir on June 6 during a routine survey for aquatic invasive species. This marks the first time that this highly invasive freshwater mussel species has been found in or near an Oregon waterbody.
Only the single quagga mussel was found. Additional intensive surveys by Portland State University (PSU) Center for Lakes and Reservoirs did not find any other mussels along the shoreline at Prineville Reservoir. Test results from water samples and environmental DNA (eDNA) tests by PSU that came back late last week also showed no sign of invasive mussels. It is unknown at this time how the quagga mussel ended up on the shore of the reservoir.
On June 6, PSU crews were conducting surveys at Prineville Reservoir and nearby waterbodies as part of their regular aquatic invasive species surveillance work around the state. On that day, surveyors located the single dead adult quagga mussel (Dreissena bugensis) on shore in sand about one meter above the waterline. They collected it and contacted ODFW, Oregon State Marine Board (OSMB) and the Oregon Invasive Species Council per established protocols.
Since the June 6 detection, ODFW and OSMB, together with federal, state and local partners, have been working under the Oregon Invasive Freshwater Mussel Rapid Response Plan. They have formed a Unified Command to coordinate continued surveillance, sampling and outreach efforts to boaters in Central Oregon and around the state.
This discovery is a serious environmental and economic concern for Oregon and the Pacific Northwest. Invasive quagga mussels are small non-native freshwater mollusks that have caused major problems in the United States since their introduction in the 1980s. They can reproduce extremely quickly and can seriously damage Oregon’s waterways. They attach to any hard surface to colonize, clog water intake systems, outcompete native species, and disrupt recreation and aquatic habitats and infrastructure.
“We are taking this finding extremely seriously, but also cautiously as we work to confirm what we’re seeing at Prineville Reservoir. We are coordinating closely with our state, federal, tribal, and local partners, and preparing to move quickly based on the evidence we find,” said Keith DeHart, ODFW Aquatic Invasive Species Coordinator. “Our top priority is protecting Oregon’s waters while making sure every action we take is grounded in the best available information.”
During surveys by PSU crews conducted in late May and early June 2026 at Prineville Reservoir, technicians completed six dock inspections covering 182 meters and surveyed 22 shorelines totaling nearly 1,500 meters. They also performed 57 mussel larva (veliger) tows—53 boat-based and four stationary near the dam—filtering more than 296,000 liters of water overall. All surveys and laboratory results from the water samples as well as Environmental DNA (eDNA) samples were negative for invasive mussels.
On June 18, ODFW staff completed inspections of two floating restrooms and their associated buoys as well as two moored vessels on Prineville Reservoir with all checks following standard invasive species protocols. No invasive freshwater mussels were detected on any structures or vessels during the survey.
Monitoring teams will continue routine intensive sampling efforts moving forward to ensure early detection and subsequent rapid response if quagga mussels are present.
Clean, Drain, Dry Recreational boats are known to be a major source of freshwater invasive mussel spread in the United States. Inspections have intercepted boats fouled by live invasive mussels prior to launching in Northwest waters a number of times in recent years. In April, ODFW staff at the Ashland Boat Inspection Station found golden mussels on a watercraft headed from the Sacramento River Delta to Oregon and were able to decontaminate the boat before it reached an Oregon waterbody.
To prevent potential dispersal of freshwater invasive mussels, boaters should: CLEAN all boats, trailers, and other equipment after leaving a lake or stream. DRAIN all water from vessels and allow them to DRY before launching into another waterbody.
Boaters are also reminded that they are required to stop at check stations for inspection. Check stations are currently located in Brookings, Ashland, Klamath Falls, Ontario and Umatilla. A roving check station will also be at boat ramps around Prineville Reservoir and central Oregon periodically in coming weeks to inspect watercraft for invasives.
Check stations and other invasive species surveillance are funded by proceeds generated by the Aquatic Invasive Species Permit and Waterway Access Permits.
ODFW and partners will continue to monitor the situation at Prineville Reservoir and regional waterbodies, allocating additional resources as needed. Expanded water and shoreline surveys are being conducted to facilitate early detection and rapid response to any signs of invasive mussels.
Public outreach including watercraft inspections is increasing. Inspections along with education materials and signage are intended to reinforce the Clean, Drain, Dry protocol with Oregon boaters.
“Continued vigilance and cooperation from the public are vital to protecting Oregon’s waters and keeping recreation areas open,” said DeHart.
There are no plans to close Prineville Reservoir at this time, as all structures and vessels inspected showed no visible mussels or signs of invasive freshwater species.
While it remains unlikely that reservoir users will encounter mussels, the public is encouraged to report any suspicious sightings to the Oregon Invasive Species Hotline at 1‑866‑INVADER or online at https://oregoninvasiveshotline.org to support ongoing monitoring and early detection efforts.
