Lake Mattamuskeet National Wildlife Refuge in Hyde County is removing thousands of invasive fish in an effort to restore water quality and aquatic grasses.
An increase in nutrients and sediment flowing into the 40,000 acre coastal lake led the N.C. Department of Environmental Quality to list the waterbody as impared in 2016. The problem is compounded by an influx of common carp, a fish that stirs up phosphorus, nitrogen, and other nutrients as it scavenges the lakebottom for food. This increases the turbidity of the water and has led to a decline in submerged aquatic vegetation. Aquatic grasses provide habitat for fish and crabs and food for migratory waterfowl.
In an effort to improve the conditions of the shallow, freshwater lake, Mattamuskeet National Wildlife Refuge along with the North Carolina Wildlife Resources Commission approved a permit to allow a commercial fisher to catch and remove carp from the lake. About 25,000 lbs of carp have been caught and transported in oxygenated tanks to catch-and-release ponds in Central North Carolina.
“The fisherman that is permitted right now, he’s baiting them with cooked corn,” said Wendy Stenton, a biologist at Mattamuskeet National Wildlife Refuge. “When he has a concentration of carp near his net, he just pulls the net together and hauls the fish out of the net and into his boat.”
A successful carp removal project took place in the 1950s when conditions of the lake were similar to present day. As a result, there were significant improvements to water quality and clarity. Increased sunlight penetration allowed submerged aquatic vegetation to return to about 16,000 acres of lakebed.
The recent carp removal project began this past summer. Based on the results of a mark and recapture population survey conducted by researchers at North Carolina State University, there is an estimated 4.4 million pounds of invasive common carp in Lake Mattamuskeet.
“To see a significant increase in water clarity,” Stanton said, “we need to remove about 75% of the carp from the lake. Currently, we have about 107 lbs of carp per acre. We need to get it down to 45 to 50 pounds of carp per acre to see significant changes in water clarity.”
The U.S. Fish and Wildlife Services, North Carolina Wildlife Resources Commission, and the Refuge are applying for grants to fund additional nets and carp exclosure gates for placement at outfall canals. The gates would prevent invasive carp from entering the lake and allow American eel, blue crab and other diadromous fish to pass freely.
“The carp removal is going hand in hand with best management practices identified in the recently approved Lake Mattamuskeet Watershed Restoration Plan to reduce excessive nutrients entering the lake,” said Stanton. “The carp removal is more of a short term project where we should be able to see significant increases in water clarity, but the long term is going to be reducing nutrients entering the lake.”