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Invasive Aquatic Species

 Hydrilla Sign at lake warning of Giant Salvinia Water Hyacinth

In order to manage and conserve our natural resources, Texas Parks and Wildlife Department enforces laws to protect our state waters against the introduction of exotic aquatic species. Fish, shellfish, and aquatic plants that are not native to Texas may compete with native animals and plants for food and space. Because introduced species lack natural enemies in their new environment, they can multiply and spread at an alarming rate, interfering with boat traffic, affecting water quality, and causing a range of other problems.

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Zebra mussels Giant Salvinia

The two species currently of greatest concern are zebra mussels and giant salvinia.

Zebra mussels

Zebra Mussels (shown here clinging to the shell of a common mussel) have been spotted in these Texas waters. If you find zebra mussels in any other Texas water body, use the report form at to alert authorities. They latch onto any hard surface in water, including rocks, rope, pipes, and other bivalves. Zebra mussels can shut down a city’s water supply by colonizing inside pipelines. They can filter out an aquatic ecosystem of its smallest nutrients, leading to declines in the fish population. They can also sink buoys and docks and damage boats, and other structures in the water. Millions of dollars are spent each year to control, clean, and monitor zebra mussels in the U.S.

Zebra Mussel Facts 



Giant Salvinia

Giant Salvinia damages aquatic ecosystems by outgrowing and replacing native plants that provide food and habitat for native animals and waterfowl. Additionally, it blocks out sunlight and decreases oxygen concentrations to the detriment of fish and other aquatic animals. When plant masses die, decomposition lowers dissolved oxygen still further. Giant salvinia infestations often expand very rapidly. It can double in about a week under the right circumstances.

Stop Aquatic Hitchhikers! Clean Recreational Equipment

Exotics often travel from one water body to another by "hitching a ride" on a watercraft. To curb the spread of these invasive species, boaters in Texas are required by law to remove harmful plants and animals from boats and trailers before leaving the vicinity of a lake, river, or bay.

Giant Salvinia clinging to a boat trailerZebra mussels on boat motor Zebra mussels on boat motor

Follow These Simple Steps

Clean- Remove all plants, animals, and mud and thoroughly wash everything, including crevices and other hidden areas.

Drain- Eliminate all water before leaving the area, including wells, ballast, and engine cooling water.

Dry- Allow time for your boat to completely dry before launching in other waters.

If your boat has been in infested waters for an extended period of time, or if you cannot perform the required steps above, you should have your boat professionally cleaned with high-pressure scalding hot water (>140°F) before transporting to any other body of water.