Aquatic Invasive Species

zebra mussel
Zebra Mussel

US Geological Survey - Amy Benson

Zebra Mussel Alert!!
Samples collected from Lake Amistad in December 2018 tested positive for zebra mussel DNA. These findings don’t indicate that live adult zebra mussels are in the waterbody. These findings place Amistad in the inconclusive status for zebra mussels, which means that there is not a reproducing population of zebra mussels at this moment at Lake Amistad.
We are providing this information to our visitors now as a reminder that boaters need to be extra careful on prevention measures when traveling to and from lakes.
In Texas, it is illegal to possess or transport zebra mussels, dead or alive. 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, this is a battle we cannot give up on!!!

A Zebra Mussel status map and full list of Texas lakes can be found on the TPWD website;
Boat Ramp sign about aquatic invasives
Boat Ramp Stencil, Box Canyon


The U.S. 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 non-indigenous to North America. Since their introduction conservation-oriented agencies 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 AMIS 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 that highlight the threat of zebra and quagga mussels (in English and Spanish since we are an international water body). Park staff gives presentations to the public, especially at fishing tournament meetings. The park also installed zebra and quagga mussel information stencils and signs during 2015 and 2016.

Person doing TOW Sampling
Amistad intern doing Tow Sampling


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 collects 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.
people doing a boat inspection
Boat inspection


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.).
Lake Amistad at Amistad National Recreation Area has 5 major boat ramps that are open to the public and selected for inspections – Box Canyon, South Winds 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 iss 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 drain their boats. From the beginning of the program in 2015 until November 2017, the park has inspected 1,415 boats. At times, the park also uses specially trained dogs to inspect for invasive mussels.

Last updated: April 2, 2019

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10477 Highway 90 West
Del Rio, TX 78840



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