Panel finds no link between Navy sonar, porpoise deaths

A scientific panel has found no evidence linking the use of Navy sonar last year in the San Juan Islands to about a dozen dead porpoises recovered in the area around the time of the incident.

The panel’s preliminary report, which was released Jan. 9, notes sonar may have played a role in the death of several animals that showed signs of trauma to the inner ear or skull. But the 14-member group uncovered no conclusive evidence tying those injuries to mid-frequency sonar used last year during a naval training exercise in Haro Strait, according to wildlife veterinarian Dr. Joe Gaydos of UC Davis’ SeaDoc Society, author of the report.

“We did find some contentious issues,” Gaydos said. “But we just couldn’t say for certain one way or the other that the trauma was caused by sonar. But we couldn’t rule it out either.”

Fourteen porpoises were recovered in and around the San Juans shortly after -- or slightly before -- the U.S.S. Shoup, an Everett-based destroyer, conducted a five-hour training exercise off the west side of San Juan Island on May 5, 2003. The panel examined 11 of the animals. Marine biologists note that finding dead porpoises in the islands is not uncommon, particularly in spring.

Gaydos said the examinations -- or necropsies -- proved difficult because of significant decay on most of the carcasses. The panel tested for toxins, parasites, and diseases, and performed a high-resolution computer tomography -- CAT scans -- on several of the animal’s skulls. Assembled by the National Oceanic and Atmospheric Administration, which oversees the National Marine Fisheries Service, the panel consisted of veterinarians, pathologists, biologists and an expert in porpoise ear anatomy.

“We aren't able to distinguish damage caused by sonar from damage caused by other agents, such as decomposition," Gaydos said.

Witnesses to the sonar episode, like Ken Balcomb of the Center for Whale Research on San Juan Island, recalled undisputed evidence of the impact sonar has had on marine mammals. Killer whales, dahl’s porpoises and a Minke whale appeared to panic and flee Haro Strait at abnormally high speed and in uncharacteristic manner as the destroyer swept through the strait. J-pod, the smallest of the three resident groups of killer whales, herded itself against the shore while the ship passed by, Balcomb said.

Balcomb said he’s “delighted” the panel conducted a thorough examination of the carcasses. The report is a significant addition to an otherwise lack of scientific evidence about effects of sonar on marine mammals, he said.

Still, Balcomb said the report avoids conclusions that confirm or deny the danger sonar poses to marine mammals, many of which -- killer whales in particular -- rely on echo-location to navigate and hunt prey. Balcomb doesn’t expect the Navy to give much attention to the panel’s report or what he insists is an overwhelming visual record of the effect of sonar on marine mammals. The Department of Defense recently was granted an exemption from federal law that protects marine mammals in the wild, he added.

“From a behavior standpoint it’s a no-brainer,” said Ken Balcomb of the Center for Whale Research, who captured much of the episode on video-tape. “There’s a clear acoustic link with behavior.”

The panel’s 60-page preliminary report was released for scientific review, and for public comment. Its final report is expected in April.

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