Invasive plant battle appears won at one lake

Indiana DNR Release:

The invasive Brazilian elodea, a plant commonly used in home aquariums, appears to have been eradicated from Griffy Lake, a 109-acre impoundment near Bloomington, after a multi-year battle waged by the Department of Natural Resources, pointing to chance for success elsewhere in the state.

"The last Brazilian elodea observed at the lake was at the beginning of the 2007 treatment season," said Doug Keller, aquatic invasive species coordinator with DNR's Division of Fish and Wildlife. "We've performed extensive searches on numerous occasions each year since the plant was last seen, and we have not been able to locate any sign of it again.

"With all the work and money put into this project to eradicate an invasive plant species new to Indiana, it is exciting to be able to claim a victory."

The suspected source of Brazilian elodea establishment in Griffy Lake was an aquarium dump likely done in the early 2000s. Cost of the project was approximately $150,000 ($1,400 per acre), including herbicide and its application, and intensive monitoring and surveys.

The DNR applied whole-lake herbicide treatments in 2006 and 2007, an aggressive plan that initially depressed the entire plant community of the lake, and that some feared might cause permanent damage to both native plant life and the fishery. Signs are that plant and fish communities are now as healthy as before the invasive plant's proliferation.

"Fortunately there is a native plant seed bank in the sediment that was just waiting to explode once the controls ceased," Keller said. "Prior to the eradication project there were typically six to seven native aquatic plant species in the lake. In the three plant surveys performed this year there were six and seven plant species again observed and they were well spread through the available habitat."

Water clarity has also improved dramatically, from 8 feet of visibility before the eradication to 13 feet this year.

Reducing aquatic vegetation, often using herbicides, is a fisheries management tool commonly employed to improve growth of panfish as a result of increased predation by bass. Dave Kittaka, DNR fisheries biologist, recently surveyed the fish community at the lake and found positive signs.

"Bluegill and redear sunfish growth and size structure increased dramatically compared to an earlier survey performed in 2004," Kittaka said. "The likely reason for the improvement was the reduction in vegetation coverage in 2006 and 2007."

The DNR will do occasional monitoring of Griffy to detect if the plant returns or other undesirable species are introduced and continue the fight elsewhere, as needed, both with treatment and education.

DNR has also eliminated Brazilian elodea from a number of smaller bodies of water, mostly in Southern Indiana, where the plant was introduced before DNR implemented regulations banning outdoor use of the plant.

"There remain a few bodies of water with Brazilian elodea we have yet to tackle but fortunately we have found tools that appear to successfully put an end to this very aggressive plant," Keller said.

The plant remains a popular species for indoor aquarium use, and that's where it needs to stay in order to prevent future costly eradication projects.

"Aquarium owners must realize the damage they can cause as a result of a seemingly innocent act such as releasing plants and fish that they have nurtured for so long," Keller said. "When no longer wanted, aquarium plants should be disposed of in household trash and unwanted fish should either be given to others who have the ability to care for them or else euthanized.

"They should never be dumped in any body of water."

Otherwise, an apparently successful, but long and expensive process may have to be redone at Griffy Lake or started at another body of water.