More than 150 melon-headed whales that stranded on a Kauai beach on July 3, 2004 were likely disoriented by sonar emitted by U.S. Navy vessels, the National Oceanic and Atmospheric Administration (NOAA) said in a final report on the incident.

The U.S. Navy was conducting RIMPAC sonar exercises off the coast of Hawaii on July 2 and 3, 2004.

"Sound propagation models suggest that sonar transmissions were likely detectable over a large area around Kauai for many hours on the day prior to the stranding, as well as within Hanalei Bay when the animals were there," said Brandon Southall, NOAA Fisheries Service's Acoustics Program Director.

"Active sonar transmissions on the 2nd and 3rd of July are a plausible, if not likely, contributing factor to the animals entering and remaining in the bay," the NOAA report states.

At the time of the stranding, the Navy was conducting RIMPAC exercises in the area, and the NOAA Fisheries Service formally requested that the Navy suspend its activities temporarily, in hopes that the whales would move farther out to sea. The Navy cooperated and ceased operations of its active sonar, and the stranding network moved the animals out of the bay.

"This event happened very quickly and the response to assist these animals was outstanding," said Bill Hogarth, NOAA Fisheries Service director. "There was a successful team effort to get these whales out of the bay. Following this event we have carefully completed the analyses of the necropsy results to determine the cause for this stranding."

Usually found in deep water, the whales swam into the shallow waters of Hanalei Bay on Kauai's north shore. The NOAA Fisheries Service notified the local marine mammal stranding network, and placed veterinarians and a response team onsite to assist the whales.

The response team used canoes and kayaks to form a flotilla and gently urge the whales back to open water. The whales were successfully moved out of the bay, with the exception of a single young calf that was found dead on July 5, 2004.

NOAA said a full necropsy did not yield a cause of death for the calf. "Results from the necropsy of the calf suggest that it died as a result of malnutrition, dehydration and stranding-related stress. We don't know why the calf was malnourished or left behind when the group was herded out of the bay," said Teri Rowles, NOAA Fisheries Service's lead marine mammal veterinarian and lead author of the report.

The U.S. Navy last week applied for a permit to again use sonar in Hawaiian waters during another RIMPAC exercise this summer. The Navy says it will turn off the sonar if marine mammals are spotted in the area of the exercises.
Provided by the Environmental News Service.