Degree of sonar harm to marine mammals debated

Whales, porpoises seen acting strangely

Scientists and whale-watchers in Haro Strait could hear the sonar long before they saw the USS Shoup.

As the pings grew louder above and beneath the waves, sounds ricocheting off submerged land forms, onlookers saw a minke whale, Dall’s porpoises and killer whales behaving strangely.

Whale expert David Bain said a minke, usually wary of research boats, was nearly run over by one. The porpoises panicked, bolting from the unnatural sounds. A pod of orcas swam into an unusual area, hid for a while, then split up, reuniting a day later.

But to the chagrin of those hoping for stronger marine mammal protections, a report by the National Marine Fisheries Service shows the difficulties in scientifically proving sonar’s impact on denizens of the deep.

At a time when scientists and environmentalists increasingly view sonar as a culprit in marine mammal deaths, such as the recent dolphin beachings at Florida’s Key West, the federal report effectively concludes that the high-powered sonar used by the Navy in 2003 did not actually harm Puget Sound orcas’ hearing.

Fisheries Service spokesman Brian Gorman said the report issued last week “shows no evidence that the intensity of the sound that the killer whales were likely to have received was sufficient to cause temporary or permanent deafness.”

The agency is still “taking seriously the possible effect of ambient sound in the environment and its effect on killer whales,” and is pursuing a killer whale recovery plan, Gorman said.

The Fisheries Service has proposed adding the resident orcas to the threatened species list. The whales, which number between 85 and 90, are classified as endangered by the state of Washington.

Some environmentalists said the analysis demonstrates increased government concern about sonar’s potentially harmful effects.

Michael Jasny, senior policy consultant for the Natural Resources Defense Council, said the report shows that the Shoup “transformed the acoustical landscape of a large area of Puget Sound.”

The “panic behavior” by marine mammals that day should lead to a common-sense “connecting of the dots,” he said.

“With this report, the government acknowledges yet again that intense military sonar harms marine mammals, including endangered orca whales,” said Joel Reynolds, director of the council’s Marine Mammal Protection Project in Santa Monica, Calif.

The highly technical assessment zooms in on one day — May 5, 2003 — in the life of Puget Sound marine mammals and the Navy.

The Shoup, a guided-missile destroyer, was the only Navy ship in the area equipped with so-called active tactical mid-frequency sonar. The ship was conducting training exercises in Haro Strait and the Strait of Juan de Fuca. The USS Momsem, also equipped with the sonar, joined the fleet at Everett last fall.

The Navy said it is committed to mitigating the potential effects of sonar on marine mammals, but active sonar is the only means of detecting modern diesel submarines, considered a serious threat to national security.

Countries such as Iran, China and North Korea are expanding their diesel submarine fleets, the Navy said, and some countries are attempting to combine diesel submarines with surface-to-surface cruise missiles with a range of 100 miles or more.

The Fisheries Service assessment includes a detailed analysis of Navy records of sonar activity, decibel levels and reverberations or echoes, hydrophone recordings, videotapes of pod behavior, and the relative distances of the ships to the whales. The report found, for example, that sonar levels received by J-pod whales ranged from 121 to 175 decibels.

Bain, a University of Washington professor who has studied whales for 25 years, said Haro Strait would register about 90 decibels if quiet — no boats, no wind or rain.

But because the impact of decibels is calculated exponentially — by how sound is perceived — a decibel range of 175 or 180 is actually heard 500 times louder than 90 decibels.

Bain said that while the federal report doesn’t show the killer whales were harmed by Navy sonar, he believes the minke whale likely suffered permanent hearing loss.

“We almost ran over it once, which makes me think it didn’t hear us,” Bain said. “It popped up 50 feet in front of us — close enough that we could smell its breath. Minkes are usually not that approachable.”

Bain said the report didn’t go far enough, and urged a more coordinated approach among scientists, particularly marine biologists.

His observations of J-pod whales ducking into an unusual cove need to be correlated to historical records to determine how usual or unusual that behavior is. He views the report as offering a piece of the overall puzzle, and has applied for a grant to study the sonar-marine mammal link more thoroughly.