Aquatic Invasive Species

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4 minutes, 51 seconds

This video provides a brief overview of Amistad National Recreation Area's aquatic invasive species program. The park would like to thank the Del Rio High School CTE Media Tech Program students from the 2021-22 academic year for their outstanding work on this video.

Zebra mussel with thumb tip and forefinger tip. Mussel is about the same size as the finger tips. Credit: USGS / Amy Benson
Though they are small, AIS--like this zebra mussel--multiply very quickly causing damage to native fish populations and civil and agricultural infrastructure, like hydroelectric dams and crop irrigation equipment.

USGS / Amy Benson

In Texas, it is illegal to possess or transport quagga or zebra mussels, dead or alive. To comply with the laws, boaters are required to drain all water from their boat and onboard receptacles before leaving or approaching a waterbody to prevent the transfer of invasive species.

Please clean, drain, and dry your boat to help prevent the spread of these mussels and other aquatic invasive species!

Amistad National Recreation Area has also been implementing various early detection and intervention measures that include sampling and testing, vessel and trailer inspections, and tools boaters can use to reduce risk of contamination.

Boat Ramp stencil about aquatic invasives stating "Stop Zebra Mussels. Clean, drain, and dry your boat. It's the law."
Reminders about how you can help protect Amistad Reservoir can be found throughout the park, like this stencil at the Box Canyon boat ramp.

NPS Photo

The United States has been invaded by two species of freshwater mussels: the zebra mussel (Dreissena polymorpha) and the quagga mussel (D. bugensis). Both are freshwater, bivalve mollusks that have a small, triangular shaped shell. Zebra and quagga mussels are Eurasian species that are not native to North America. Since their introduction, conservation-oriented bureaus, such as the National Park Service, have attempted to protect unaffected lakes from invasion and to slow the spread of mussels to new areas. A prevention program specifically targeting zebra and quagga mussels (ZQM) has been in place at Amistad National Recreation Area since 2014, beginning with public outreach and education as the first step in the collective efforts to prevent the introduction of Dreissena mussels.The park has brochures in both English and Spanish that highlight the threat of zebra and quagga mussels. Park staff give presentations to the public, especially at fishing tournament meetings. The park also installed zebra and quagga mussel information stencils and signs in 2015 and 2016.

Woman with white net doing Tow Sampling at the end of a dock with Amistad Reservoir in the background.
Amistad intern performing tow sampling.

NPS Photo

Early detection is one of the most important steps to initiate containment activities, which will help prevent the spread of invasive mussels to other water bodies. Resource Management staff have settlement samplers, which are inspected monthly at docks and deep water areas adjacent to the boat ramps and Amistad Dam. In addition to the settlement samplers, park staff collect water samples to be tested for zebra and quagga mussel veligers (microscopic larvae). Vertical plankton tows are used to collect samples for analysis using Cross Polarized Light Microscopy (CPL) and/or quantitative Polymerase Chain Reaction (q-PCR) analysis at independent laboratories. Water sampling efforts have been concentrated near marinas, boat launches, and Amistad Dam.

Dog handler in orange shirt and blue jeans with black lab sniffing motor of trailered boat on a road.
Boat inspection with a Mussel Dog specially trained to detect these aquatic invasive species.

NPS Photo

Another element of early detection and intervention, Amistad National Recreation Area launched a watercraft inspection program in 2015. The goals of the program include inspecting incoming boats for zebra and quagga mussels, educating boaters about the risks of invasion, notifying boaters of recent regulations, and gathering information relevant to zebra and quagga mussel spread from boaters (i.e. how well they clean their vessel, how often they visit infested/suspect lakes, etc.).

Amistad Reservoir has 5 major boat ramps that are open to the public and selected for inspections – Box Canyon, Southwinds Marina, Diablo East, Black Brush, and Rough Canyon. Inspectors stop incoming boats for a survey and a brief entrance inspection to look for mussels. If a boat is exceptionally dirty or has visited an infected/suspect lake in the last 30 days without decontamination, it is deemed “high risk” and is given a more rigorous search. Boaters that are leaving the lake are also surveyed and are reminded to clean, drain, and dry their boats. From the beginning of the program in 2015 until September 2023, the park has inspected 14,269 boats. At times, the park also uses specially trained dogs to inspect for invasive mussels; to this day, the park has completed 6,295 of these inspections.

Thirty-one Texas lakes across five river basins are currently (as of August 2022) classified as "infested" by Texas Parks and Wildlife with zebra mussels, meaning that the water body has an established, reproducing population. Compare this to 24 Texas lakes classified as infested in March 2021, less than a year and a half earlier.

An invasive mussel status map and full list of Texas lakes can be found on the TPWD website:

More about Lake Amistad's status can be found at

Permanently mounted AIS CD3 unit with hoses lights and ads with statements "Stop Invasive Species," "Clean. Drain. Dry.", and "Everyone Likes a Clean Boat" on attached panels.
Amistad's CD3 Unit at Box Canyon

NPS / J Guindin

Providing an additional layer of early intervention, Amistad has installed several free, watercraft cleaning systems that help keep the boater in compliance with Clean, Drain, and Dry principles. These waterless, boater-operated units are located at the Diablo East, Southwinds, Rough Canyon, and Box Canyon boat ramps. Often called "CD3 Units" (for Clean, Drain, Dry, and Dispose -- the last "D" being a reference to bait), these units have the tools necessary to help a boater minimize the risk of contamination from their watercraft and trailer, including a wet-dry vaccuum, blower, grabber, and brush.

We need your help to slow the spread of aquatic invasive species. Please use all the tools available at Amistad National Recreation Area and other bodies of water when boating at these locations.

Amistad National Recreation Area

Last updated: September 5, 2023