Aquatic Invasive Species — Ballast Water Management and the Nonindigenous Aquatic Nuisance Prevention Act

Zebra mussels arrived in the Great Lakes in the 1980s in the ballast water of oceangoing ships — emptied into American ports as vessels loaded cargo. Since then, they have colonized more than 500 bodies of water across North America, fouling water intake pipes, smothering native clams, and fundamentally altering aquatic ecosystems wherever they establish. They are among the most costly environmental invasions in American history. The federal response is the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 (NANPCA), codified at 16 U.S.C. §§ 4701–4751, which established the first federal regime specifically targeting aquatic invasive species — mandating ballast water management for ships entering U.S. waters, creating a national Aquatic Nuisance Species Task Force, and directing federal resources toward detection, control, and public outreach for species like sea lamprey, Asian carp, green crab, and hundreds of others that continue to threaten native fisheries and water infrastructure across the country.

Current Law (2026)

Legal Authority

• 16 U.S.C. § 4701 — Findings and purposes: Congress finds that the introduction of nonindigenous species into U.S. waters is a significant threat to the ecological and economic health of aquatic ecosystems; the purpose of the Act is to prevent the introduction and spread of nonindigenous aquatic species into U.S. waters, to provide for the management of invasions, and to minimize the economic and ecological impacts of such species
• 16 U.S.C. § 4711 — Ballast water management for vessels equipped with ballast water tanks: ships equipped with ballast water tanks that operate on the waters of the United States are required to carry out ballast water management practices; the Coast Guard administers these requirements; the standard has evolved over time from mid-ocean ballast water exchange to performance-based treatment system standards
• 16 U.S.C. § 4712 — National ballast water management information: requires studies, surveys, and maintenance of a national data center on ballast water practices and aquatic species introductions; information is used to update management requirements as science evolves
• 16 U.S.C. § 4721 — Aquatic Nuisance Species Task Force: establishes an interagency task force co-chaired by the FWS Director and the NOAA Administrator; additional members include the EPA Administrator, the Army Corps of Engineers Chief of Engineers, the Coast Guard Commandant, the BLM Director, the Forest Service Chief, and others; the Task Force coordinates federal aquatic invasive species policy
• 16 U.S.C. § 4722 — Aquatic nuisance species program: directs the Task Force to develop and implement a program for the waters of the United States to prevent introduction of aquatic nuisance species, detect their presence, monitor infested waters, control their spread, and conduct public education; the program must address prevention, early detection, rapid response, control and management, monitoring, outreach, and research
• 16 U.S.C. § 4723 — Regional coordination: the Task Force must coordinate with the Great Lakes Commission and regional entities; regional panels can develop regional management plans that supplement the national program with locally appropriate measures
• 16 U.S.C. § 4728 — State management plans: states may develop aquatic nuisance species management plans for submission to the Task Force; approved state plans receive federal technical and financial assistance; state plans must address prevention, monitoring, control, and restoration

How Ballast Water Spreads Invasive Species

Ocean-going ships take on millions of gallons of seawater as ballast when they offload cargo and discharge it when loading in destination ports. This ballast water contains whatever organisms were present when it was loaded — larvae, eggs, bacteria, algae, fish, invertebrates. A single large vessel can carry thousands of species in its ballast tanks.

The zebra mussel (Dreissena polymorpha) entered the Great Lakes in ballast water discharged in Lake St. Clair around 1986. Within a decade it had colonized every Great Lake and spread throughout the Mississippi River drainage. Zebra mussel infestations have cost billions of dollars in cleaning water intake pipes for utilities and municipal water systems; they filter vast quantities of algae from the water column, disrupting food webs and depleting the base of the aquatic food chain. The related quagga mussel has further extended the invasion.

NANPCA responded by requiring ships entering U.S. ports from beyond the Exclusive Economic Zone to exchange their ballast water in the open ocean before entering freshwater ports — the theory being that open-ocean organisms would not survive in freshwater. The 1996 National Invasive Species Act strengthened these requirements. Modern standards, promulgated by the Coast Guard, require ships to use ballast water treatment systems that kill organisms to specific performance standards rather than relying solely on exchange.

The Great Lakes: Ground Zero for Aquatic Invasions

The Great Lakes have received more aquatic invasive species than any other body of water in North America, in part because of their historic position as a major shipping destination connected to the ocean via the St. Lawrence Seaway. More than 180 nonindigenous species have established in the Great Lakes basin since European settlement, with major invasions including:

Sea lamprey: The sea lamprey (Petromyzon marinus) entered the upper Great Lakes through the Welland Canal and devastated native lake trout populations in the mid-20th century. The Anadromous Fish Conservation Act provides the federal domestic authority to fund cooperative fishery restoration that supports Great Lakes Fishery Commission objectives on the U.S. side. The Great Lakes Fishery Commission has managed sea lamprey control since 1955 through a combination of chemical treatment (lampricide) and barrier dams on spawning streams. The program has reduced sea lamprey populations by roughly 90% from their peak, at a cost of approximately $20 million annually.

Asian carp: Bighead and silver carp, introduced to aquaculture ponds in the southeastern United States and escaped into the Mississippi River system, have spread northward toward the Great Lakes. These filter-feeding fish can reach 100 pounds, consume vast quantities of plankton, and out-compete native species. Electric barriers at Chicago's waterway connection between the Mississippi and Lake Michigan have slowed their entry into the Great Lakes, but carp have been detected in waters above the barriers. Billions of dollars in economic damage to commercial and sport fisheries could result if carp establish in the Great Lakes.

Hydrilla and other aquatic plants: Dense mats of invasive aquatic plants block light, alter water temperature, deplete dissolved oxygen, and impede navigation. Many were introduced through the ornamental aquarium and water garden trades.

How It Affects You

If you own a boat: Recreational boaters are the primary pathway for spreading aquatic invasive species between water bodies. The EXPLORE Act (Section 8426) gives federal land agencies authority to inspect and clean watercraft entering or leaving federal waters to prevent invasive species spread. Invasive species — including zebra mussels, Eurasian watermilfoil, hydrilla, and round goby — attach to boat hulls, trailers, and equipment and can establish in any new water body where a boat is launched. "Clean, Drain, Dry" requirements posted at public boat launches are legally mandated under state laws that implement the NANPCA framework. Failing to clean equipment can carry civil and criminal penalties in most states.

If you live near the Great Lakes or other affected water bodies: The economic cost of aquatic invasive species falls on communities through higher water treatment costs, declining fisheries, reduced tourism revenue, and degraded recreational water quality. The NANPCA programs represent an attempt to share those costs at the federal level rather than leaving affected communities to absorb them entirely.

If you work in shipping or commercial maritime transportation: The Coast Guard ballast water management requirements apply to any vessel operating on U.S. waters that is equipped with ballast water tanks. Vessels that entered service before 2009 face retrofitting deadlines; new vessels must meet performance standards from commissioning. The Coast Guard type-approval program certifies ballast water treatment systems that satisfy the performance standards.

If you work in fisheries management or freshwater ecology: State fish and wildlife agencies funded through Pittman-Robertson and Dingell-Johnson excise tax programs often use those funds for invasive species control on wildlife management areas. The Task Force programs coordinate federal and state responses to new invasive species detections. Early detection and rapid response — the most cost-effective phase of invasive species management — requires coordinated monitoring networks that NANPCA helps fund and coordinate. Understanding NANPCA's framework is essential for state and federal fisheries managers.

State Variations

States have significant roles in aquatic invasive species management. Most states have their own invasive species lists, decontamination requirements, and enforcement programs. State boat launch inspection programs, funded in part through NANPCA cooperative agreements, are the primary point of contact between recreational boaters and invasive species requirements. States in the Great Lakes basin coordinate through the Council of Great Lakes Governors on management priorities. Some states — particularly Wisconsin, Minnesota, and Michigan — have more aggressive programs than federal minimum requirements.

Pending Legislation

Asian carp management legislation has been periodically enacted as amendments to NANPCA and through standalone bills. The Great Lakes Restoration Initiative, authorized and annually appropriated, funds NANPCA-related programs. Interest in strengthening ballast water treatment standards and closing loopholes for ships operating entirely within the Great Lakes has been sustained in Congress. No major amendments to the core NANPCA framework are pending as of 2026, but the ongoing threat from new potential invasions — golden mussel, new carp variants, aquatic pathogens — keeps the issue on the congressional agenda.

Recent Developments

The golden mussel (Limnoperna fortunei), a prolific filter feeder native to Asia, has been spreading through South America and was detected in U.S. waters in 2024, triggering rapid response programs under the NANPCA framework. Asian carp management at the Chicago waterway connection has proceeded with construction of new barrier infrastructure, though the ultimate solution of permanent hydrological separation between the Mississippi and Great Lakes basins remains politically and logistically contentious. The Coast Guard finalized updated ballast water treatment performance standards that took full effect for existing vessels in recent years, completing the transition from exchange-based to treatment-based management.