NOAA 2002-090
Contact: Connie Barclay
NOAA News Releases 2002
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Today, the National Oceanic and Atmospheric Administration's National Marine Fisheries Service announced measures designed to provide protection of marine mammals when the United States Navy operates its Surveillance Towed Array Sensor System Low Frequency Active Sonar, or SURTASS LFA sonar. Under this authorization, the U.S. Navy is granted an exemption under the Marine Mammal Protection Act in order to operate up to two SURTASS LFA systems over a five-year period.

To meet requirements under the MMPA, the U.S. Navy conducted research to assess possible effects of the new sonar system and sought the advice of NOAA Fisheries on the best safeguards to employ when operating the sonar. NOAA is an agency of the U.S. Commerce Department.

NOAA Fisheries determined – based on research, stringent monitoring requirements, and strong mitigation measures outlined by the agency for the Navy – that marine mammals are unlikely to be injured by the sonar activities and that the sonar will have no more than a negligible impact on marine mammal species and stocks.

The U.S. Navy's LFA sonar uses a low frequency (about 300 Hz) underwater sound source to locate submarines at long ranges. The LFA sonar operates at a much lower frequency than the standard tactical sonar (approximately 3500 Hz) currently used by the Navy. LFA sonar has not been operated since research in preparation for this authorization concluded in late 1998.

According to the U.S. Navy, the SURTASS LFA sonar system meets their need for improved detection and tracking of new-generation submarines at a longer range. It maximizes the opportunity for U.S. armed forces to safely react to, and defend against, potential submarine threats, while remaining a safe distance beyond a submarine's effective weapons range.

NOAA Fisheries officials outlined several measures to prevent the potential for injury to marine mammals and sea turtles, including establishing several protected areas and sonar shutdown criteria. Some of the measures include:

  • The U.S. Navy will conduct visual monitoring, and both passive and active sonar monitoring, to ensure that marine mammals and sea turtles are detected before they enter the area where LFA Sonar would be used.
  • The U.S. Navy will shutdown the LFA sonar whenever marine mammals or sea turtles are detected. Detection is expected to be almost 100 percent effective up to 2 km (1.1 nautical miles or 6,562 ft) from the sound source. It has been determined that at 1 km, the LFA sound has diminished to a level that would not cause harm to marine mammals.
  • The U.S. Navy will limit the upper frequency of LFA sonar to 330 Hz to prevent non-auditory injury.
  • The U.S. Navy is prohibited from using SURTASS LFA sonar within 12 nautical miles of all coastlines and in designated marine mammal biologically important areas.
  • Marine mammals that frequent only coastal, estuarine, and polar environments would not be affected, since the system will not be operated in coastal waters or polar seas.
  • The U.S. Navy is required to continue research on effects of low frequency sounds on marine mammals.

The SURTASS LFA authorization requires the Navy to investigate several questions left unanswered by previous LFA research, including responses of sperm and beaked whales to LFA signals, behavioral responses to sub injurious sound levels, and long-term silencing effect of LFA signals on whale calls. If this research discovers risks, appropriate mitigation measures are to be developed.

The U.S. Navy requested the authorization from NOAA Fisheries to harass marine mammals incidental to operating SURTASS LFA sonar because it has the potential to affect marine mammals. Section 101(a)(5) of the MMPA allows the incidental "take" or harassment of small numbers of marine mammals.

NOAA Fisheries has determined, based on the best science available, that these takings will have no more than a negligible impact on the affected species, will not have an unmitigable adverse impact on the availability of these species or stock(s) for subsistence uses, and regulations have been prescribed setting forth the permissible methods of taking and the requirements pertaining to the monitoring and reporting of such taking.

The authorization will be reviewed on an annual basis. Based on monitoring and reporting records kept by trained Navy personnel, NOAA Fisheries will assess impacts on marine mammal populations annually, and renew, modify or suspend the authorization, depending on the review. NOAA Fisheries can also immediately revoke the SURTASS LFA authorization if it is determined that impacts on marine mammals are more than negligible.

NOAA Fisheries received more than 10,000 letters on this action. Officials reviewed all of the comments and addressed all significant issues of concern in making the final decision on this matter. Examples of significant issues include: effects of resonance on marine mammals, whether the taking results in small numbers, and whether the total taking will have no more than a negligible impact on marine mammals and long-term cumulative effect on the environment.

NOAA Fisheries is dedicated to protecting and preserving our nation's living marine resources through scientific research, management, enforcement, and the conservation of marine mammals and other protected marine species and their habitat.

To learn more about NOAA Fisheries please visit