Author: Laura Oleniacz
For a handful of lakes in western and central North Carolina this summer, a nibbling fish will play a role in the control of an invasive aquatic plant.
DWR’s Aquatic Weed Control Program received permits from the North Carolina Wildlife Resources Commission (WRC) to stock sterile grass carp in certain lakes this spring in central and western North Carolina to control hydrilla, an invasive aquatic plant.
DWR staff partnered with local governments, water utilities and others to release nearly 7,100 sterile carp in April and May. The fish were stocked in the Lake Benson, Cane Creek Reservoir, Lake James, Mountain Island Lake, Lake Norman, Lake Tillery and in small ponds in Orange County in the Eno River watershed.
Environmentally Speaking sat down with Andrew Gay, aquatic weed specialist for DWR, to learn more about the sterile carp release and hydrilla.
What is hydrilla?
Hydrilla is a non-native invasive plant brought over through the aquarium trade. Outside of its native habitat, hydrilla can outcompete native vegetation; it can make thick mats that can impede boating or swimming. It can clog a municipal water intake.
What are sterile grass carp?
Grass carp are an herbivorous fish native to Asia. In the United States, sterile triploid grass carp are used as a biological control agent for invasive hydrilla. They typically form schools and graze the hydrilla as it sprouts and continues to grow.
Why do they have to be sterile?
They have to be sterile because they’re a nonnative species. They prefer to eat hydrilla, but they will eat other vegetation, and the native vegetation is good for reducing nutrients in the lake, and it gives habitat for many aquatic critters, especially for younger fish. There would be potential for them to start degrading habitat quality in some of our rivers or even estuaries if they were to get that far.
How do local governments and utilities become eligible?
DWR’s Aquatic Weeds program addresses issues with noxious aquatic weeds as determined by state statute. We work with units of local government or other partners to cost-share the purchase of the sterile grass carp. The cost-share program is set up where DEQ pays for 50% and the local cooperator pays for the other 50%. There is a process to get a permit from the North Carolina Wildlife Resources Commission (WRC) for a specific location. The first step is to submit an application to WRC. It then goes through a review process called a biological investigation. Depending on the location, they will coordinate with other state or federal agencies as needed, if there are any rare or endangered species, or species of concern. Once they have reviewed the permit and coordinated with other agencies as needed, they will either approve or deny the permit.
What should you do if you catch one of the fish?
Because they are strictly herbivorous, they are not commonly caught on a hook and line. If you catch one, just throw it back.
What is the process to get the carp to North Carolina?
First, we do an aquatic vegetation survey in the fall. We survey the shoreline of the lake, mapping out the hydrilla to give us an estimate for how much hydrilla is out there. We have a model we developed with the WRC to determine the number of fish we need. We are able to plug in the number of hydrilla acres and then it gives us a recommended number of fish to stock. Once we receive the permit approval, we purchase the fish from a farm, which will check to make sure they’re sterile, or all triploid. For our larger stockings (>2,000 fish), they are loaded onto a tractor trailer and delivered to each site. We are there to assist with getting the fish into the lake. We typically release them in the early spring when the water temperatures are lower. They have a whole summer to get acclimated to the lake, eat and be able to survive the winter. For the smaller stockings, the fish are purchased from a local pond management company and then delivered to the site with a tank on a pick-up truck or trailer.