Yellowstone National Park Requests Help In Preventing Spread Of Aquatic Invasive Species

Yellowstone National Park is reminding boaters and anglers to clean, drain and dry all boats, trailers and equipment prior to arriving in the park to help stop the spread of aquatic invasive species (AIS) into park waters. There is an increased risk of invasion by highly invasive zebra and quagga mussels in Yellowstone following recent detections in waterways within a day’s drive of the park (2025 upper Colorado River in Colorado; 2022 Pactola Reservoir in South Dakota; and 2023 Snake River in Idaho).

Yellowstone National Park straddles the Continental Divide and is located at the headwaters of the Yellowstone, Snake, and Missouri River drainages, which flow into the Gulf and Pacific Ocean drainages. Mussels have caused irreversible ecological damage and extensive impacts to infrastructure and recreation in waterways throughout the Midwestern and Eastern United States, as well as in the lower Colorado River Basin.

In both 2022 and 2023, Yellowstone’s AIS inspectors intercepted and denied launch to mussel-fouled watercraft, highlighting the urgency and severity of the threat. In 2025, inspectors at Grand Teton National Park south of Yellowstone intercepted a mussel-fouled watercraft that was bound for Yellowstone Lake.

To help prevent the spread of AIS, boaters should clean all plants, animals, mud, sand and other debris from your boat, anchor, boots and equipment using high-pressure, hot (120-140 F) water, if possible. They should also drain all water from the boat, including the motor, bilge, livewell and other compartments before arriving and dry all compartments and equipment in the sun until thoroughly dry.

To protect park waters and respond to the growing AIS threat, there is a 30-day dry time requirement for sailboats and certain motorized boats prior to launching. Non-motorized watercraft and vessels with outboard motors are exempt from this requirement. Large, trailered watercraft pose the highest risk of transporting and introducing invasive mussels and other AIS because they are difficult to inspect and less likely to be completely drained/dried or fully decontaminated. Manual decontamination with the use of hot water is not always 100 percent effective in removing all mussels, and a 30-day dry time will mitigate the risk.

Any motorized or non-motorized watercraft previously fouled by mussels, regardless of dry time, will be denied launch. The launch of fouled watercraft increases the chances of false mussel detection by routine environmental DNA monitoring of park waters, which could result in significant impacts to operations and public recreational opportunities.

These proactive measures are required to ensure the long-term ecological integrity of park waters and downstream mussel-free waters in Wyoming, Montana, and Idaho. Failure to prevent invasion by zebra and quagga mussels could result in widespread negative impacts to natural resources, recreational values and local businesses, and could undo over two decades of work to restore native Yellowstone cutthroat trout to the park. Prevention of an AIS introduction is critical because there are no effective eradication methods, and control/containment is both costly and environmentally consequential.