AUDREY McAVOY Associated Press Writer | Posted: Friday, April 28, 2006 12:00 am
HONOLULU (AP) - The Navy's use of sonar during maritime exercises may have contributed to the mass stranding of more than 150 whales in Kauai's Hanalei Bay two years ago, government scientists said Thursday.
The National Oceanic and Atmospheric Administration said this conclusion - along with information from other studies - has led it to ask the Navy to adjust how it uses sonar during similar exercises planned for this summer in Hawaiian waters.
The Navy plans to comply with the agency's request. It notes, however, that the report did not conclusively show sonar triggered the stranding.
Brandon Southall, director of NOAA's acoustics program, said officials were unable to find other reasons - weather-related or otherwise - that may have caused the melon-headed whales, named because of the bulge in their foreheads, to swim en masse into the shallow waters off the North Shore of the Hawaiian island of Kauai on July 3, 2004.
But officials also lacked evidence to definitively say sonar caused the incident, he said.
"It's possible this was one of what may have been a number of contributing factors," Southall told reporters in a conference call. "It's plausible."
Nearby predators or other factors may have also contributed to the incident, NOAA said in its report on the stranding released Thursday.
The Navy uses sonar technology, which bounces sound waves off underwater objects to map underwater geography, to detect threats and to navigate.
But some wildlife advocates believe the sound waves hurt whales, possibly by damaging their hearing or causing them to rise to the surface too quickly and get decompression sickness.
The Navy was holding its biennial Rim of the Pacific maritime exercises off Hawaii at the time of the incident two years ago.
More than 40 ships, seven submarines, 100 aircraft and some 18,000 troops from eight countries converged on the Hawaiian islands for the monthlong series of drills.
The day before the whales entered Hanalei Bay, a group of six U.S. and Japanese vessels steamed north from Oahu toward Kauai, using active sonar signals intermittently along the way.
NOAA's study concluded the whales may have heard these signals and headed into shallow waters as a result.
All the whales - except for one calf - left the bay after about 28 hours with the guidance of volunteers on canoes and kayaks.
A necropsy of the calf, which was later found dead, showed the mammal likely died of malnutrition, dehydration, and stress related to the stranding. The necropsy found no sign the whale suffered trauma due to loud sounds, NOAA said.
The Navy downplayed the inferences that could be read from the report.
"There are data limitations and the report is inconclusive," said Lt. Cmdr. Christy Hagen, a spokeswoman for the U.S. Pacific Fleet. "There are so many unknown factors that you cannot come to any definitive conclusion at this point."
Lt. William Marks, a Navy spokesman at the Pentagon, said the six-hour gap between the last use of sonar and the arrival of the whales in the bay made it unlikely sonar triggered the stranding.
But environmentalists said the report clearly blamed sonar.
"It adds to a long and growing list of strandings that have been associated with the Navy's use of sonar," said Michael Jasny, a senior consultant with the Natural Resources Defense Council in Los Angeles.
"Together it paints a picture of a global problem," he said, citing other mass strandings in the Canary Islands, Alaska and Japan.
In light of the Hanalei incident and strandings in the Bahamas and elsewhere, NOAA said it has asked the Navy to reduce its sonar's power during this summer's Rim of the Pacific exercises when its ships detect marine mammals nearby.
The agency also asked the Navy to turn off its active sonar when the animals come within a set distance.
Donna Wieting, deputy director for the office of protected resources at NOAA's Fisheries Service, said she was confident these steps would minimize the impact of the exercises on marine mammals.
She said she believed sonar would likely only prompt "temporary behavior modifications" in the animals during the drills.
But Jasny said the measures would fail to prevent strandings because the Navy would be allowed to use the same sonar in the same places as in 2004.
The Rim of the Pacific exercises, also known as RIMPAC, have been held off Hawaii 19 times since 1968. The incident two years ago marked the first time whale strandings were noticed during the drills.