Lake Norman & Mooresville

Carp to make a meal of hydrilla menace

Lake Norman, one of the state's premiere waterways, attracts tens of thousands of boating, swimming and fishing enthusiasts each year.

However, there's something else which the lake also attracts annually in the thousands: hydrilla, recognized as the most problematic aquatic plant in the United States.

In an attempt to contain the invasive submersed hydrilla plant, the Lake Norman Marine Commission will stock the lake with sterile grass carp again this year. The fish consume the hydrilla, according to Bob Elliot, chairman of the Lake Norman Marine Commission's hydrilla committee.

It's an ongoing effort to keep the threat in check.

"Consistent annual use of carp is the most cost-effective way to control the hydrilla," said Elliot. "I would expect that we will be putting 1,200 carp into the lake by the end of May."

Elliot says this will be the sixth year carp have been introduced into the lake in order to control hydrilla growth.

This year, the carp supply should cost about $7,200 with the expenses shared between the state, Duke Energy, Charlotte Mecklenburg Utilities and the four counties that border the lake.

Hydrilla is native to central Africa but is now found in temperate and tropical regions around the world. It apparently entered the United States as an aquarium plant, and was sold to retail aquarium dealers across the country.

In 1960 it was first discovered growing wild in Florida. Since its introduction in Florida, hydrilla has spread across the southern United States from the Atlantic Coast as far north as Washington, D.C., across the Gulf Coast into Texas, and west into Arizona and California.

Hydrilla is usually a submersed plant, but it can grow to the surface and form dense mats thick enough for ducks to walk on. The plant stems are slender, branched and up to 25 feet long.

It was first found in Lake Norman in 2000.

Elliot says there have been parts of the lake where the concentration of hydrilla has been so thick it has prevented boats from reaching docks behind waterfront homes.

"Without identifying specific locations, I know that their presence has had an impact on the sale of some waterfront homes in the Lake Norman area," said Elliot.

In addition to the economic impact, hydrilla can make swimming, boating, fishing and water-skiing difficult and dangerous, clog water intake systems, shade out desirable aquatic plants and provide breeding habitat for mosquitoes and other pests.

The carp that officials use to battle the pesky growth live for as long as six years and will grow to sizes of 4 feet to 5 feet. The fish are sterile and it is illegal to catch and keep them.

Lake Norman is by no means the only waterway in North Carolina where hydrilla can be found. Officials at Lake Wylie have been wrestling with the weed for several years with limited success, using a combination of carp and herbicides.

"Herbicides are expensive and essentially worthless," Elliot said.

"The best approach, in my opinion, is what we do: Stock the waters with carp year after year."

According to the N.C. Agricultural Extension Service, the long life expectancy of the sterile carp makes them "a very attractive alternative to expensive herbicides."