North Carolina removed invasive carp from Lake Mattamuskeet in a restoration effort; an earlier removal campaign increased water clarity more than fourfold and expanded underwater grasses by 16,000 acres

Lake Mattamuskeet, North Carolina’s largest natural freshwater lake, has gone through a dramatic transformation, and the cause traces back to a fish most Americans have never heard of: the common carp. According to the U.S. Fish and Wildlife Service’s restoration project page, historic carp removal efforts during the 1940s and 1950s increased the lake’s water clarity from less than 0.5 feet to over 2 feet, more than a four-fold improvement, and allowed underwater grasses to expand across an estimated 16,000 acres of lakebed.

Why a bottom-feeder became public enemy number one

Common carp are not native to the United States; they were brought over from Europe starting on the 1800s and have since become one of America's most problematic invasive species. As stated on the FWS project's website, common carp unearth underwater plant beds while feeding and digging in the lake or riverbed and also kick up sediment that reduces water clarity, sunlight penetration, and the ability of aquatic plants to photosynthesize. In Lake Mattamuskeet's case, this was especially problematic for underwater grasses that typically grow in shallow waters (averaging 3 feet deep in Mattamuskeet). These plants were completely gone by 2017, according to an annual survey by refuge staff, representing an almost total loss of these critical species.

This loss of plants was a serious blow to the local ecosystem, as Lake Mattamuskeet is on the Atlantic Flyway and is a vital wintering ground for tens of thousands of tundra swans as well as a breeding ground for numerous waterfowl. It also supports species like bass, crappie, and blue crab populations that are of local importance. The proliferation of algae blooms was also linked to the reduction of these plants, and the lake was placed on the state's impaired waters list in 2016 by the N.C. Division of Water Quality. A 2017 research paper titled “Where's the Grass? Disappearing Submerged Aquatic Vegetation and Declining Water Quality in Lake Mattamuskeet,” published by Moorman et al. in the Journal of Fish and Wildlife Management found that cyanotoxins, including cylindrospermopsin, at some of the highest concentrations recorded in U.S. lakes, were present in the lake’s water samples.

Bringing back a 1950s-era solution

A removal program was launched in 2019 by the Fish and Wildlife Service and the North Carolina Wildlife Resources Commission that employed the same techniques that were used in the 1950s. This involved removing the carp entirely from the lake and putting in place barriers to prevent the remaining carp from returning to the lake via outfall canals so that the grasses had a chance to recover.

The project has received a $1 million federal grant and further funding through the Bipartisan Infrastructure Law and involved the installation of carp exclusion structures, the hiring of commercial fishermen to remove tens of thousands of pounds of carp from the lake, and the stocking of bluegill to prey upon the carp's eggs and fry. Some early tests showed promise for this method, as indicated by Piehler in the final progress report titled “Assessing the Potential for Ecosystem Enhancement in Lake Mattamuskeet: Final Progress Report,” published by the U.S. Fish and Wildlife Service. Per the report, wild celery that was planted in carp-proof enclosures had lasted for several months longer than plants that were not planted in these enclosures but did not survive for more than a year.

Here is the surprising twist that may change the conditions for years to come

A technical report titled “Population Monitoring, Movement, and Removal of Common Carp in Lake Mattamuskeet, NC,” published by USFWS in May 2026, found that most of the carp remaining in the lake after the removal project wrapped up in February were older, in poor health, and not actively reproducing, with population levels already below what’s needed to sustain the group. In other words, the carp population may already have been collapsing on its own, independent of the removal effort. This doesn’t necessarily mean the restoration project failed, water clarity and grass coverage are still being tracked, but it’s a reminder that cause and effect in ecosystem restoration are often harder to untangle than a single before-and-after snapshot suggests.