Texas Parks & Wildlife Magazine   


Know These Nuisances

By Earl Chilton

Help keep alien plants from spreading through Texas waters.

Nuisance plants can be ecologically detrimental to fish and wildlife resources, and limit access for fishing, hunting and other recreational activities. For example, researchers have found that overabundant vegetation can decrease the growth and average size of largemouth bass.

In general, aquatic plants that have become nuisances in Texas are not native to the state. None of Texas' three most troublesome aquatic plants - hydrilla, water hyacinth and giant salvinia - are native to North America.

Want to help protect boating, fishing, hunting and swimming in Texas? Then make sure you can identify nuisance plants and are not introducing them into other bodies of water.

Here's how to identify these top three aquatic nuisance plants:

  1. Water hyacinth (Eichhornia crassipes): This large floating plant is often called the world's worst aquatic weed. Water hyacinth reproduces by budding daughter plants, or by producing seeds when its beautiful purple flower blooms. Populations may double in size every six to 18 days. Water hyacinth can shade out beds of submerged vegetation, eliminate plants that are important to waterfowl, and induce low oxygen concentrations that precipitate fish kills. The combination of large leaves and hanging roots can cause the loss of up to 13 times as much water to the atmosphere as normal evaporation without the plant.
  2. Hydrilla (Hydrilla verticillata): A submerged plant species, hydrilla has small (1/2 to 1 inch) leaves arranged in whorls around the stem. Hydrilla can grow very fast (up to 1 inch per day), producing dense surface mats that may cause fluctuations in dissolved oxygen levels, pH and temperature, as well as inhibiting water flow, boating, fishing and swimming. Overabundant hydrilla can reduce plant and animal diversity, and stunt sport-fish populations. Nearly half of fragments with at least a single leaf whorl can grow into a new plant. Hydrilla tubers can dry out for several days and still remain viable. Buried in wet sediment, they can live for years.
  3. Common salvinia (Salvinia minima) and giant salvinia (Salvinia molesta): Both common and giant salvinia are small, floating aquatic ferns with oval leaves that have tiny hairs on the upper surface. Common salvinia is readily distinguished from giant salvinia by its leaf hairs. In common salvinia, the hairs are split four ways near the tip, whereas in giant salvinia, the hairs are also split, but they come together at the tip, forming an egg-beater-like structure. Typically, the mature leaves of giant salvinia are about twice the size of common salvinia. Giant salvinia damages aquatic ecosystems by outgrowing and replacing native plants. Additionally, giant salvinia has been known to grow up to three feet thick, blocking out sunlight and decreasing oxygen, and thereby killing fish and other aquatic species.

To ensure that you're not adding to the spread of invasive species, follow these procedures:

  1. Remove any visible plants, mud, fish or animals before transporting equipment.
  2. Eliminate water from equipment before transporting.
  3. Clean and dry anything that came in contact with water (boats, trailers, equipment, etc.).
  4. Never release plants, fish or animals into a body of water unless they came out of that body of water.

For more information on invasive species and aquatic hitchhikers, visit www.protectyourwaters.net.

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