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Active Military Sonar and Marine Mammals: Events and References

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Publication Date: February 2007

Publisher(s): Library of Congress. Congressional Research Service

Series: RL33133

Topic: Environment (Ocean and ocean resources)


The deployment of active sonar by the U.S. Navy and its potential impacts on marine mammals has been an ongoing issue of intense debate; regulatory, legislative, and judicial activity; and international concern. Some peacetime use of military sonar has been regulated under the Marine Mammal Protection Act (MMPA) and other statutes due to concerns that active military sonars are operated at frequencies used by some cetaceans (i.e., whales, porpoises, and dolphins), and their highintensity sound pulses may travel long distances in the ocean. There is also concern that sonar transmissions of sufficiently high intensity might physically damage the hearing in cetaceans or cause them to modify their behavior in ways that are detrimental. Although mid-frequency sonar has been implicated in several beaked whale strandings, there is scientific uncertainty surrounding the totality of the effects active sonar transmissions may have on marine mammals.

This report summarizes legal and political events related to active sonar and marine mammals since 1994. Prior to the late 1990s, concerns focused primarily on the use of underwater sound as a research tool. While strandings and mortality of marine mammals, primarily beaked whales, have been observed in concurrence with mid-frequency sonar operation, additional controversy has focused on the development of low-frequency active (LFA) sonar. Environmental interests are concerned with LFA sonar because low-frequency sound travels farther than midfrequency sound and is closer in frequency to those known to be used by baleen whales.

Additional questions involve how to balance obligations of the military to comply with MMPA provisions (as well as provisions of the National Environmental Policy Act and the Endangered Species Act) with national security concerns. In 2003, Congress passed P.L. 108-136, wherein ยง319 amended the MMPA to authorize exemptions from restrictions on harassing and otherwise taking marine mammals for "national defense."

Generally speaking, concern about the environmental effects of ocean noise is now principally focused on three activities -- military sonar exercises, oil and gas exploration, and commercial shipping. This report summarizes some of the more significant recent events pertaining to active military sonar, in particular.