When 300 Asian grass carp are released in Lake Wylie on May 12, they will have an important job.
The sterile, plant-eating fish eat Hydrilla, an aggressive aquatic plant that, when left unchecked, can choke the lake and cause environmental and economic damage, said Ken Manuel, a senior scientist at Duke Energy.
In the United States, it is estimated that invasive aquatic plants account for loses of $120 billion per year, according to the Council for Agricultural Science and Technology (CAST).
Every segment of Hydrilla that breaks off can create a new infestation, Manuel said. Hydrilla is capable of infesting lakes 20-25 feet deep. In Lake Wylie, the potential for growth spans 3,400 acres.
The plant can grow so dense that it can clog water sources and make recreational and economic activities impossible. It also can clog drainage systems and lower the dissolved oxygen in the water that fish and other sea life needs to survive.
Duke Energy partners with the N.C. Wildlife Resources Commission, the N.C. Department of Environment and Natural Resources - Aquatic Weed Program, and the Lake Wylie Marine Commission to keep Hydrilla and other invasive aquatic plants in check, Manuel said.
The South Carolina Department of Natural Resources and other stakeholders was consulted about the Lake Wylie Marine Commission Management plan that had been approved by N.C. natural resurce agencies, according to the Marine Commission.
Thanks to the efforts of the involved parties, Hydrilla has been kept under control in Lake Wylie, said George Medler, a Lake Wylie Marine commissioner for York County.
“We’re pretty well protected and covered here because of the efforts being made by the Marine Commission and Duke,” he said. “We’ve got it well under control.”
Hydrilla also can pose threats to the water crucial for Duke Energy to produce electricity, Manuel said. It also can affect municipal drinking water.
“We have to constantly pay attention to our water sources,” he said.
Through Duke Energy’s Mosquito Control Program, which sends boat crews on Lake Wylie in May through October to control mosquito populations and check for invasive plant species, Hydrilla was first spotted in Lake Wylie in 2006, Manuel said.
“We figured it would be just a matter of time before we saw it,” he said.
Efforts to get rid of the plant began immediately with crews spraying herbicide, Manuel said. The initial infestation was estimated at 90 acres. Herbicides slow growth, but it’s an expensive control method, Manuel said. In 2008, Duke coordinated with the North Carolina Marine Commission and N.C. Wildlife REsources Commission to stock sterile grass carp in Lake Wylie to eat the Hydrilla.
The grass carp eat the leafy part of Hydrilla, but can’t reach the tubers, the part of the stem that grows beneath the soil, Manuel said. It can take years to completely eradicate the nutrients packaged in the tubers.
Since 2008, 3,376 grass carp have been put in Lake Wylie, Manuel said.
He said Hydrilla growth has not reached the South Carolina side of the Lake Wylie.
The Lake Wylie Marine Commission, N.C. Aquatic Weeds Program, and Duke Energy share the costs of controlling Hydrilla, with the state picking up half the cost, said Rob Emens, N.C. Aquatic Weed Control Program manager.
The cost for adding 300 grass carp this year will be $2,640, Manuel said.
North Carolina’s Shallow Draft Navigation Channel Dredging and Lake Management Fund allows for up to $500,000 to be used for the state’s Aquatic Weed Program, according to the N.C. Department of Environment and Natural Resources.
The state is considering a vegetation survey of Lake Wylie to see what may need to be done, Emens said. That would cost about $7,000, which would be shared between the state, Lake Wylie Marine Commission and Duke Energy.
“We are overdue for that,” he said.
The key to invasive plant species control along Lake Wylie is “early detection, rapid response,” Manuel said.
Amanda Harris is a freelance writer. Have a story idea for Amanda? Email her at firstname.lastname@example.org.
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Because Hydrilla can survive six to eight hours outside of the water and often attaches itself to boats and ramps, the most common way the plant gets into other bodies of water is through human transport, Manuel said.
▪ Remove visible aquatic plants, animals and mud before leaving the water access point.
▪ Report new infestations of aquatic plants or animals to the N.C. Department of Agriculture and Consumer Services.
▪ Drain water from boats, motors, live wells and bait containers.
▪ Dispose of unwanted bait and aquatic plants in the trash
▪ Spray recreational equipment and boats for nonvisible species before leaving the water access point and before entering another body of water
Source: Stop Aquatic Hitchhikers, an effort of the Aquatic Nuisance Species (ANS) Task Force sponsored by the U.S. Fish and Wildlife Service.