Aquatic Nuisance Species

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.

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.

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. 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. 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:

Aquatic Nuisance Species

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In September 2023, Apple Snail egg clusters were found in multiple sites along the Lumber River in Lumberton. Samples of these clusters were submitted to the NC Museum of Natural Sciences who confirmed the identification of Apple Snail eggs.  This is the first currently known population in NC, but Apple Snails are a globally problematic invasive species.

Native to South America, Apple snails have been introduced in Europe, Asia, and multiple US states in the past. Their grazing habits can cause damage to agricultural crops such as rice, as well as to wild native plants used by many aquatic species; they have even been observed feeding on amphibian eggs. Additionally, there are human health risks as: adult snails carry rat lungworm, which can infect humans if eaten raw or undercooked, causing a potentially fatal disease. The snail’s egg masses also contain a toxin which can cause skin and eye rashes if they contact bare skin.

Apple Snails are most easily recognized by their distinctive large, bright pink egg clusters, laid on solid surfaces, such as tree trucks, concrete, or other vegetation, above the waterline along the edges of streams, rivers or ponds. When the eggs hatch, the young snails drop into the water, where they grow into fully aquatic adults, reaching two to six inches in size (much larger than any of our native aquatic snails). Female snails lay eggs as often as once a week, which allows populations to grow and spread rapidly once established.  The species is often confused with mystery snails, another group of invasive aquatic snails. Mystery snail shells form a point; the whorls of the shell rise to a point, forming a cone shape. Apple snails shell are circular and rounded with no point.

If you see a suspected Apple snail or an egg mass, please take a photograph and record the location and report it to the NCWRC’s Aquatic Nuisance Species Reporting Tool. After documenting the location, egg masses can be destroyed crushing and scraping them off into the water with any implement such as a stick or a boat paddle, making sure the eggs sink, but you should avoid touching them with bare skin. Adult snails can be destroyed by crushing or freezing.    

apple snail

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.


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 via the NCWRC’s Aquatic Nuisance Species Reporting Tool, 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.

Hydrilla (Hydrilla verticillata) is a highly destructive, nonnative aquatic plant found on both the Federal Noxious Weed List and the N.C. Department of Environmental Quality's Aquatic Weed List. Hydrilla creates nearly impenetrable mats of stems and leaves of the surface of lakes, rivers and other waterways. An invasive species from Asia, hydrilla crowds out native vegetation, reduces recreational opportunities, and ultimately can harm fish and other aquatic organisms, as well as bird species. The plant can also clog intakes where rivers or reservoirs are used for drinking water supplies and irrigation. It is considered one of the worst aquatic weeds in the United States. Hydrilla is also known as water thyme, Florida elodea, Wasserquirl and Indian star-vine.

Hydrilla can reproduce in four different ways; fragmentation, tubers, turions, and seed:

  • Fragmented pieces of hydrilla that contain at least one node or whorl are capable of sprouting into a new plant.
  • The tubers (roots) of hydrilla are formed on the rhizomes (underground stem) and each one can produce 6,000 new tubers.
  • Turions (buds) formed in the leaf axils of the plant can break off, settle in the sediment, and sprout into a new plant.
  • Seed production is mostly used for long distance dispersal by means of ingestion by birds.

Native to parts of Asia, Africa, and Australia, it was first introduced to Florida in the 1950s through the aquarium trade. By the 1970s, the plant had invaded every major drainage basin in Florida. Currently, hydrilla has become established from Florida to Connecticut and west to California and Washington, with the most severe occurrences being found in the Gulf and South Atlantic States. In North Carolina, hydrilla is considered the number 1 invasive aquatic species. It is found in various waters throughout the state, from the mountains to the coast, in reservoirs, natural lakes, rivers, and coastal sounds.

Management Efforts

Harris Lake Hydrilla Management

Harris Lake is a reservoir in New Hill that covers 4,100 acres in southwestern Wake County and southeastern Chatham County. Hydrilla was first reported in Harris Lake in 1988. In September 2018, the Division of Water Resources’ (DWR) Aquatic Weed Control Program conducted a submerged aquatic plant survey at Harris Lake that identified 232 acres of hydrilla. Harris Lake is a source population for the spread of hydrilla to other waterbodies in our state, where the long-term environmental and economic impacts can be substantial. To reduce the risk of hydrilla spreading beyond Harris Lake, DWR plans to stock sterile grass carp to control hydrilla and treat around boat ramps with herbicides to reduce the chance of it spreading to other waterbodies on boats, boat trailers or other equipment. In conjunction with DWR, the Commission is implementing a five-year Harris Lake Habitat aquatic habitat enhancement project to establish approximately 30 acres of artificial and natural structures and approximately one acre of founder colonies of native vegetation.

Eno River Hydrilla Management

Hydrilla was first observed in the main stem of the Eno River in 2005 and has since infested over 20 miles of river in Orange and Durham counties. In 2013, the formation of the Eno River Hydrilla Management Task Force created a partnership between multiple government agencies, North Carolina State University, and non-profit organizations to address the growing concern over the infestation. The result of this collaboration was the installation of an herbicidal drip system that releases a low concentration of fluridone into the river during hydrilla’s growing season, beginning in the spring and continuing into the early fall months. 

Mystery snails were introduced to the U.S. in the late 1800s. Their current distribution in North Carolina includes the following lakes: Gaston, Hickory, Jordan, Norman and Wylie. They can be found in the Neuse, Yadkin and Pee Dee rivers. Their native range is Southeast Asia to Russia including Japan, Korea and Taiwan. Their habitat consists of lakes and reservoirs with sand, silt and mud substrate, although it can survive in slower regions of streams as well. The snails are known to clog screens of water intake pipes and heat exchangers in power plants. If consumed, they have the potential to be vectors for the transmission of parasites and diseases.

On July 27, 2015, whirling disease was confirmed in rainbow trout collected from Watauga River in Watauga County– the first occurrence of the disease in North Carolina. Whirling disease affects fish in the trout and salmon family with rainbow and brook trout, two species found in North Carolina waters, being the most susceptible. The disease, caused by the microscopic parasite Myxobolus cerebralis, damages cartilage and skeletal tissue in trout, causing them to swim in a whirling motion. While often fatal to juvenile trout, the disease does not infect humans or pets, and eating an infected fish is not known to cause any harmful effects. Whirling Disease Frequently Asked Questions

Contact the Commission if you observe signs of whirling disease in fish.

Submit a Whirling Disease Observation


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:

  1. Larval: Live freely in the water column, allowing them to be easily transported.
  2. Juvenile: prefer a hard or rocky substrate, they have been known to attach to vegetation.
  3. Adult: Can live for several days outside of water and are common hitchhikers on boats, fishing equipment and aquarium plants.

Think you’ve found a zebra mussel? Please take a photograph and record the location and report it to the NCWRC’s Aquatic Nuisance Species Reporting Tool.

Zebra Mussel Fact Sheet - 2023 (NC Wildlife Resources Commission)

Zebra Mussel Fact Sheet (U.S. Geological Survey website)

Preventing the Spread of Invasive Zebra and Quagga Mussels: A Reference Guide for Methods of Decontaminating Gear and Equipment” (Invasive Mussel Collaborative)

Guidance for SCUBA divers and Snorkelers

Zebra Mussels in Moss Balls



Help Stop the Spread of Aquatic Nuisance Species

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

How Can You Help?

Do not transport live fish from one water body to another.

Even if a fish looks fine on the outside, it may carry the parasites or other pathogens and can introduce disease. Illegal stockings can result in unwanted introductions that can have irreversible consequences. The Commission requires a stocking permit to stock any fish into North Carolina’s public waters.

Carefully clean all equipment after fishing.

Rinse all mud, dirt, sand and all visible plants, fish and animals from equipment (see list below). Aquatic nuisance species are known to adhere to these kinds of materials and can potentially be carried on gear from one stream to another. Careful cleaning using disinfectants such as household bleach will kill all forms of the parasite and reduces the risk of spreading this and other aquatic nuisance species. Remember to rinse your equipment thoroughly after using bleach to prevent this chemical from entering bodies of water.

  • Examples of fishing equipment that should be cleaned:
  • anchors
  • buckets
  • boots/shoes/waders
  • boat and trailer
  • creels
  • downriggers
  • fishing rods and reels
  • fishing line
  • lures
  • nets
  • props
  • ropes
  • trolling motor
  • wading stick
  • wading gear
  • and other items used in and around the water

Dispose of fish parts carefully when cleaning fish.

Dry disposal is best; dispose of the carcass in the garbage, by deep burying, or by total burning. Please do not dispose of fish heads, skeletons or entrails in any body of water. This can spread parasites and disease. Also, don’t discard entrails or heads of fish down a garbage disposal. Many parasites can survive most water treatment plants and infect areas downstream.

Boaters - Take these 4 steps after each trip on the water:

  1. Clean: Equipment of all aquatic plants, animals and mud.
  2. Drain: Water from boats, live wells, bait buckets and all equipment.
  3. Dry: All equipment thoroughly
  4. Never Move: Fish, plants or other organisms from one body of water to another.

How You Can Stop the Spread of Aquatic Nuisance Species

The N.C. Wildlife Resources Commission, along with other state and federal agencies, developed the N.C. Aquatic Nuisance Species Management 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.