Study: Sonar Use Can Injure Marine Mammals

by Sherry Morse

New research published this month documents how the use of sonar devices can seriously harm whales and other marine mammals and suggests that the Navy should be more careful about its use.

The research team, led by Paul Jepson of the Institute of Zoology in London, concluded that the deaths of fourteen whales near the Canary Islands last year were most likely caused by exposure to high frequency sonar waves.

The sonar appears to have caused nitrogen gas bubbles to form in the whales’ vital organs, which caused a fatal illness similar to the decompression sickness that deep sea divers get if they surface too quickly.

Spanish-led international naval exercises nearby were using high frequency sonar at the time.

Jepson said it is unclear how decompression sickness would occur in whales and other mammals who commonly dive to great depths, but what is known is that the mammals who strand themselves most often when sonar is used are deep diving mammals who tend to have large levels of nitrogen in their tissues.

John Hildebrand, who studies marine mammal acoustics at the Scripps Institution of Oceanography in La Jolla, California, said Jepson’s study "has the potential to be the ‘smoking gun’ on the cause of sonar-related mammal strandings."

The report has led at least one advocacy group, People for Puget Sound, to call for the US Navy to suspend testing of powerful sonar in Washington State’s inland waters.

Kathy Fletcher, executive director of People for Puget Sound, said, "The Navy could reassure all of us who are working hard to prevent the extinction of our resident orca whales if they would announce that they will immediately stop all high-intensity sonar drills and tests in the sensitive inland waters of Puget Sound and the Northwest Straits."

Jepson’s report has ironically appeared at a time when the United States Congress is considering loosening regulations governing the use of high volume sonars in the ocean. The oceans subcommittee of the House of Representatives Committee on Resources is currently looking at a measure which will weaken the 1972 Marine Mammal Protection Act which provides protective guidelines for the use of noisy experiments in the ocean. The measure would make it easier to obtain permits for these experiments, and make marine mammals more vulnerable.

A House-Senate conference committee is also currently considering a measure that would exempt the US Navy from the regulations on the grounds of national security.

The Navy’s use of some sonar devices has been limited under an agreement reached in early October with the Natural Resources Defense Council.

Under the terms of the agreement, which must be approved by a federal magistrate before it becomes permanent, the Navy would be restricted to using its new sonar system only in specific areas along the eastern seaboard of Asia. The Navy also agreed to seasonal restrictions designed to protect whale migrations.

The regulatory changes are supported by the Navy and by some geophysicists who want to study geological formations on the ocean floor. However, many marine biologists strongly oppose any changes to the current regulations.

Members of the European Parliament recently delivered a petition with 100,000 signatures to NATO headquarters, calling for a ban on sonar devices in the light of Jepson’s new research.

© 2003 Animal News Center, Inc.