National Aquatic Invasive Species Act of 2003

National Aquatic Invasive Species Act of 2003 - Amends the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 to establish aquatic invasive species prevention requirements for vessels (including towed vessels) operating in U.S. waters. Requires the Secretary of the department in which the Coast Guard is operating to promulgate regulations for ballast water management standards and certification procedures.

Directs the Aquatic Invasive Species Task Force to establish a priority pathway management program that identifies those pathways that pose the highest risk for the introduction of aquatic invasive species unless further managed.

Prohibits the importation of live aquatic organisms not in trade without specified screening and approval.

Requires the Assistant Secretary of the Army for Civil Works, with the concurrence of the Administrator of the Environmental Protection Agency, to construct and maintain a national dispersal barrier program to prevent the spread of aquatic invasive species in U.S. waterways.

Provides for expansion of the Brown Tree Snake Control Program and Aquatic Nuisance Species Program information, education, and outreach activities. Requires the Task Force to establish a national subcommittee on nutria for its control.

Requires the National Oceanic and Atmospheric Administration (NOAA), the Smithsonian Environmental Research Center, and the U.S. Geological Survey (Administering Agencies) to develop and conduct a marine and freshwater research program to assess rates of, patterns of, and conditions surrounding introductions of nonnative aquatic species in aquatic ecosystems and efforts to prevent the introduction of, and detect and eradicate, such species.

Requires the Environmental Protection Agency (EPA) to develop a grant program to fund research, development, demonstration and verification of environmentally sound cost-effective technologies and methods to control and eradicate aquatic invasive species.

Requires the Coast Guard and the EPA to develop a research program to support implementation of vessel pathway standards to prevent the introduction and spread of aquatic invasive species by vessels.

Requires the National Science Foundation to establish a grant program for researchers at institutions of higher education and museums to carry out research in systematic and taxonomy.

Requires the Invasive Species Council to coordinate with the Task Force to combat aquatic invasive species. Requires the Task Force to recommend to appropriate Federal agencies additions to the list of aquatic invasive species.

Requires the Task Force, the Council, and the Secretary of State to ensure that international efforts to prevent, detect, monitor, assess, and control aquatic invasive species are coordinated with U.S. policies.