Aquatic Nuisance Species

What is an Aquatic Nuisance Species (ANS)? An aquatic nuisance species is a nonnative species that has been introduced and is known to be causing ecological or economic harm. Not every nonnative aquatic species is a problem. Some don’t occur in great numbers or create significant ecological or economic harm; others have important commercial or recreational value. 


Why are ANS a Problem? North Carolina has abundant and diverse water resources. Protecting them is important to support the state’s unique biological attributes and growing population and economy. Nationally, economic loses attributed to ANS total billions of dollars annually.


How did ANS get in North Carolina? 75% of the ANS in North Carolina have been introduced from other areas of North America. Humans are the cause in nearly all introductions, either through unintentional or deliberate actions. Over 60% of ANS fish species in NC were introduced by intentional stocking or bait release. Additional pathways include direct stockings from private aquaculture facilities into public waters, cultivated species cultivated species that escaped captivity, “hitchhiking” on recreational or commercial watercraft, and aquarium releases.


While there are more than 300 species of freshwater and marine plants, animals and pathogens currently in North Carolina, below are the ones anglers, boaters and outdoor enthusiasts are most likely to encounter. We urge everyone to know what they are, how to identify them, and how to prevent their spread. Whirling disease and gill lice are two aquatic nuisance species found in trout in western North Carolina, while didymo is a nuisance algae that has been seen in the Tuckasegee River in Jackson County. Hydrilla, an highly invasive aquatic plant, is found in freshwater lakes and ponds across the state. Learn more about each of these below. 


The N.C. Wildlife Resources Commission, along with other state and federal agencies, developed the N.C. Aquatic Nuisance Species Managment Plan to improve the state’s ability to address aquatic invasive and aquatic nuisance species with the goal of preventing and controlling their introduction, spread, and negative impacts. Download a copy of the N.C. Aquatic Nuisance Species Management Plan. (PDF - 11 MB)


Harris Lake Hydrilla Management Project

Zebra Mussels

Note: On March 5, 2021, Zebra mussels have been confirmed in moss balls sold at retailers in North Carolina, including PetSmart. If you have purchased moss balls in the past month, please follow the instructions below about how to properly destroy them and clean your aquariums. Known packaging reads 'Marimo Moss Ball Plant Grab & Go' and 'Mini Marimo Moss Balls', but there are likely more brands that contain the mussels. An overabundance of caution is suggested if you've purchases ANY moss balls recently.  Read more here.


The U.S. Fish and Wildlife Service has created an informational webpage dedicated to what to do if you have purchased aquatic moss balls in the past month. DESTROY! DON'T DUMP!


Read our Frequently Asked Questions document for more information on Zebra Mussels.


Zebra mussels, small, fingernail-sized mollusks native to the Caspian Sea region of Asia, are regarded as one of the most troublesome invasive species in North America. In spite of their small size, zebra mussels clog pipelines used for water filtration, render beaches unusable, and damage boats. They also negatively impact aquatic ecosystems by harming native organisms.

The zebra mussel is a small shellfish named for the striped pattern of its shell. However, color patterns can vary to the point of having only dark or light-colored shells with no stripes.  Zebra mussels have three life stages:

Larval: Live freely in the water column, allowing them to be easily transported.

Juvenile: prefer a hard or rocky substrate, they have been known to attach to vegetation. 

Adult: Can live for several days outside of water and are common hitchhikers on boats, fishing equipment and aquarium plants.

Zebra Mussel fact sheet (USGS website)

Whirling Disease

Myxobolus cerebralis (the parasite that causes whirling disease) was first confirmed in North Carolina in July 2015 from a Rainbow Trout collected from Watauga River near Foscoe, Watauga County. Whirling disease damages cartilage and skeletal tissue in a fish, causing it to swim in a whirling motion. While often fatal to juvenile fish, the disease does not infect humans or pets, and eating an infected fish is not known to cause any harmful effects. The NCWRC will continues to work with researchers to explore the distribution and life history characteristics of Myxobolus cerebralis in North Carolina.

Learn more about whirling disease.

Gill Lice

In September 2014, gill lice (tiny, white copepods that attach to a fish's gills) were documented in North Carolina. Elsewhere within the United States, Salmincola edwardsii and S. californiensis are known to parasitize salmonids of the genera of Salvelinus and Oncorhynchus, respectively, and taxonomic and molecular analyses of copepods confirmed the identification of both species in the State, with S. edwardsii infecting Brook Trout and S. californiensis infecting Rainbow Trout. Gill lice can traumatize gills and inhibit the fish’s ability to breathe. While most fish are able to tolerate a moderate infestation of gill lice, if they’re suffering from other stressors, such as drought and high water temperatures, population impacts are more likely to occur. Anglers have been asked to report observations of gill lice during recreational outings, while the NCWRC continues to sample Brook Trout and Rainbow Trout populations across the mountains of North Carolina to document the distribution and status the copepods.



Researchers from Tennessee Tech University collected cells of the microscopic algae in Tuckasegee River, Jackson County, while conducting regional surveys in late 2015 – the first time the organism has been documented in North Carolina. Didymo, also called rock snot, is the common name of Didymosphenia geminata, a freshwater diatom species that can produce thick algal mats along stream bottoms. The mats can be so thick that they alter stream habitats and make fishing difficult.



Hydrilla is a submersed aquatic plant that can create nearly impenetrable mats of stems and leaves on the surface of lakes, rivers and other waterways. An invasive species from Asia, hydrilla impedes recreational use of waterways, crowds out native vegetation and can ultimately harm fish and other aquatic species. The plant can also clog intakes where rivers or reservoirs are used for drinking water supplies and irrigation.

Learn more about hydrilla

Stop the Spread of ANS

Aquatic nuisance species are plants and animals introduced into waters that cause ecological and/or economic harm if established. Aquatic nuisance species include whirling disease, didymo, gill lice, hydrilla, zebra mussel, giant salvinia and many others. 

Help stop the spread of aquatic nuisance species. Take these four steps after each trip on the water:

CLEAN: Equipment of all aquatic plants, animals and mud.

DRAIN: Water from boats, live wells, bait buckets and all equipment.

DRY: All equipment thoroughly

NEVER MOVE: Fish, plants or other organisms from one body of water to another.



For more information on how to stop aquatic hitchhikers, visit:






Protect Your Waters!


ANS Photos

Cleaning Your Boat Properly

Stocking Permit Info

Stop before You Stock! Stocking Permit Required for Public Waters!

To protect native or legally established aquatic species from the potentially damaging effects of unauthorized stockings, the N.C. Wildlife Resources Commission requires anyone wishing to stock a public, inland fishing water in North Carolina with fish, mussels or crustaceans to obtain a stocking permit issued by the agency's Inland Fisheries Division. Learn more about Fish Stocking Permits.