Ivnasive Species

The Invasive Species Group is composed of Ana, Jessica, Itajha, Glen, and Flor T. This group studies the invasive species that are present in Sheldon Lake, including plants and animals. They research many different facts pertaining to their history, where they came from, the reason they are invasive and ways they are controlled.

What is an Invasive species?
"Exotic or invasive species are organisms-microorganisms, plants and animals-that have moved beyond their natural habitat and are competing with native species for food and territory. Invasions can be accidental or intentional, but the risk to native species is great in either instance. Exotic species compete with native species, alter habitats, change predator/prey relationships, and transmit foreign diseases or parasites. Exotic species also can cause a myriad of problems (food chain disruption, reduced biodiversity, clogging of water intakes, increased weed growth) and cannot be eliminated from a system without causing increased harm. Early detection and rapid response are essential to prevent major damage to ecosystems and the economy."

Species	Where did it come from?	How is it invasive?	How is it being controlled?
Grass Carp	It is native to rivers in China and the Soviet Union. They were brought to the U.S. In the early 1960's to control overgrowths of aquatic plant material in waterways.	It has the potential to do incredible damage to native plant species and natural habitats because they consume the aquatic vegetation in large amounts.	It is being controlled by being stocked in designated body of water of Texas, like Lake Conroe.
Nutria	It was brought from South America to Louisiana in the 1930's. Since then, they have stretched out and gone as far as to the wetlands of the Gulf of Mexico's coastal borders.	They are very destructive grazers of wetland marshes because they dig up and feed upon the root systems of mash plants.	Their populations are usually small and controlled. They are mainly controlled by the large populations of alligators that eat them.
Chinese Tallow Tree	The plant was purposely introduced into Southeastern U.S. as early as the 1700's. It comes from China where it has been cultivated for about 1,500 years as seed crop.	It spreads rapidly, is difficult to kill, and takes over large areas by out competing native plants. It can even thrive in well drained uplands and bottomlands. It is continued to be sold in plant nurseries.	Severe population of the Chinese Tallow can be controlled with broadcast application of Grazon or Tordon in the spring or fall. Individual plants may be controlled with spot application of Velpar or with basal stem treatment.
Water Hyacicnth	Water hyacinth is thought to be native to the Amazon River basin of South America. It was introduced to the United States in 1884 at the Cotton States Exposition in New Orleans, Louisiana. It spread across the southeastern U. S. and was identified in Florida in 1895. It was reported to be in California in 1904.	It forms dense mats that interfere with navigation, recreation, irrigation, and power generation. These mats competitively exclude native submersed and floating-leaved plants. Low oxygen conditions develop beneath water hyacinth mats and the dense floating mats impede water flow and create good breeding conditions for mosquitoes.	Three insects have been released for the biological control of water hyacinth. These include two weevil species and a moth. Instead insect predation reduced plant height, decreased the number of seeds produced, and decreased the seasonal growth of the plants. This, in turn, allowed better boat access into plant mats, reduced use of herbicides, and resulted in less plant problems.
Salvinia	First reported as established outside of cultivation in the United States in 1995 in a pond in Southeastern South Carolina. It was first observed in Texas in 1995.	It floats on top of the water making it difficult for other species to get sunlight. It gets its nutrients directly from floating roots in the water taking away nutrients from other species in the ecosystem. They are asexual so they can take over an area quickly.	The Salvinia weevil is a biological control agent for the Salvinia. It causes damage to plants by tunneling through rhizomes and feeding on terminal buds.
Hydrilla	It originated from Southern India. The monoecious type is from Korea. It was introduced to the Tampa and Miami, Florida areas as an aquarium plant in the late 1950's. By the 1970's it was established throughout Florida. It spread to Texas by boats and trailers as fragments.	It forms dense stands from the bottom to the top of the water, sprawling across the surface. It shades out ecologically important native plants. It clogs irrigation and flood-control canals. It interferes with boating and prevents swimming and fishing. It alters the water chemistry and oxygen levels.	Million of dollars are spent each year on herbicides and mechanical harvesters in effort to place Hydrilla under "maintenance control". They are removed from the lakes, and then the plants die and decompose. Mechanical harvesters and chopping machines remove it from the water and transport it to a disposal shore. Biocontrol is also used with fish and insects. They eat the Hydrilla.

Invasive Species of Sheldon Lake