Corps Requests Funds For Grass Carp Study To Battle Clarks Hill Hydrilla

After more than five years of studies and discussion, the U.S. Army Corps of Engineers will ask Congress to fund an Environmental Assessment to determine if sterile grass carp can be introduced to Clarks Hill Lake to control hydrilla.

Hydrilla at Clarks Hill has been linked to an algae bloom and neurotoxin responsible for the deaths of 76 bald eagles. The 70,000-acre reservoir is one of just 17 waterways across the southeast where the condition— known as avian vacuolar myelinopathy, or AVM—has been confirmed. The deadly algae grows on hydrilla, which is a favored food for coots, which are then eaten by bald eagles. The algae-born AVM creates lesions inside the brain that cause fatigue, disorientation and death.

Despite efforts to control hydrilla after its discovery in the lake in 1995, the initial 55-acre path has expanded steadily to cover an estimated 7,300 acres today, said corps conservation biologist Ken Boyd.

The use of grass carp to reduce or slow the spread of hydrilla has been discussed for several years. Such a step, however, is both costly and controversial, since it would add a large new species to the lake.

Scott Hyatt, the lake’s operations project manager, cited a 2013 survey by the University of Georgia in which stakeholders in the region were supportive of stocking the carp.

Corps biologist Ken Boyd with a clump of hydrilla from the Cherokee Recreation Area at Clarks Hill, where the weed was first identified in 1995. It has expanded to more than 7,300 acres.

“Generally, users were in support of reducing hydrilla, with 84.5 percent of respondents preferring either less hydrilla or only native aquatic plants,” the survey concluded. Users were also largely receptive to stocking grass carp, with 74.3 percent either “indifferent” to or “in support.”

On the downside, the dense mats of hydrilla create cover favored by fish—and fishermen. Hydrilla has also attracted ducks to Clarks Hill. Concerns have also been aired over whether grass carp would also eliminate native aquatic plants.

Introducing the fish would require input from authorities on both sides of the lake, which straddles the Georgia-South Carolina border along the Savannah River. It would also require funding for enough fish to do the job.

The next step in the process, Hyatt said, will be a request for funds for a formal environmental assessment. The request will be incorporated into the project’s fiscal 2016 budget request, which is under preparation this year. Even if funds for an assessment were promptly approved, it could take several years before carp could be approved and added to the lake.