Sonar possible cause in death of rare dolphin

A rare dolphin died on the beach of the Navy's San Nicolas Island, about 60 miles west of Los Angeles, in late January during the final days of Navy exercises using a type of sonar that has been linked to fatal injuries in whales and dolphins.

Although researchers have yet to determine a cause of death, a dissection of the right whale dolphin's head revealed blood and other fluid in the ears and ear canals. The same symptoms were found in deep-diving whales that washed ashore in the Canary Islands and the Bahamas after military sonar exercises.

Unlike the mass strandings of whales on the Canary Islands in 2002 and the Bahamas in 2000, only one dolphin washed ashore Jan. 29 on San Nicolas. That occurred just as the Navy's 3rd Fleet in San Diego was wrapping up sonar training that has become the focus of a federal court fight and elicited an effort by President Bush to intervene.

Teri Rowles, lead veterinarian with the National Oceanic and Atmospheric Administration, cautioned against jumping to conclusions until a panel of expert radiologists could review magnetic resonance images of the dolphin's head and a federal pathologist could scrutinize tissues for diseases as well as for air and fat bubbles associated with sonar-related injuries.

"At this point, we cannot rule in or rule out sonar or any other kind of intense noise," said Rowles, head of the nation's Marine Mammal Health and Stranding Response Program. "This one is perplexing at this point."

The dolphin death comes at a delicate time for the Navy, which has appealed a federal court order imposing extra safeguards to protect whales from possible harm caused by midfrequency active sonar.

"During the last 40 years, there has been no documented incidents of harm, injury or death of marine mammals resulting from exposure to (midfrequency active) sonar" in Southern California waters, the Navy stated in its 77-page appeal filed last week.

Lawyers for the Navy argue that a federal court order has no scientific basis to require the Navy to shut down sonar when marine mammals are spotted within 2,200 yards and to avoid areas along the coast and between some of California's Channel Islands that are known for their abundance of marine mammals. These and other court-imposed conditions, Navy officials said, hamper the ability to train sailors to use sonar to detect quiet-running diesel-electric submarines now operated by Iran, China, North Korea and other potentially hostile nations.

The 9th U.S. Circuit Court of Appeals has promised to rule on the Navy's latest appeal by March 3, so the Navy will have time to petition the Supreme Court before its next two rounds of sonar testing, scheduled to begin in March.

The female dolphin, at 6 feet 9 inches, first washed ashore alive, and Navy personnel pushed it back into the water several times in an attempt to save it before it finally died on the beach. The Navy flew the carcass to Santa Barbara Airport, where curators at the Santa Barbara Museum of Natural History picked it up and performed a necropsy.

"The lesions that we have seen to date are consistent to what has been found in whales in the Canary Islands and the Bahamas," Rowles said.

The most telling indications will not come until pathologists can complete microscopic examination of the brain, the ears and other tissues to look for gas or fat bubbles and related hemorrhaging.

That's what showed up in the acoustic jaws, ears, brain and kidneys in 10 of 14 beaked whales that died after international naval exercises using midfrequency sonar.

Scientists in the journal Nature theorized that these deep-diving whales might have panicked and bolted to the surface, causing decompression sickness, similar to the "bends" or air embolisms that can affect human divers. The problem arises when gas bubbles, compressed under the pressure of depth, expand rapidly and tear delicate tissues.

The microscopic analysis of most tissues should take about a month, Rowles said. It could take as long as a year to examine the ears, because the bones must be slowly dissolved in fluid to peek at soft tissues inside.

Rowles expects lab results within a week to determine whether the dolphin was poisoned by a neurotoxin called domoic acid that is produced by an algae that blooms in California waters.

Joe Cordaro, a wildlife biologist with the National Marine Fisheries Service, said about 20,000 right whale dolphins live in waters off California, Oregon and Washington. Strandings of these animals occur rarely, seldom more than once or twice per year, he said.

Right whale dolphins are social animals, seen gamboling in pods of hundreds. So if the death is linked to sonar, it would be unusual that only one animal washed ashore, he said.