Researchers tag whales, track ships in sonar study

NORFOLK

Debate has long raged over how the military's use of sonar to detect enemy submarines affects dolphins and whales, which use sound to navigate, communicate and locate food.

Now, researchers are moving closer to getting some solid answers.

In a scientific first, experts tagged dozens of whales with sensors to track their movement and behavior while Navy ships operated nearby.

The research in Hawaii coincided with the Navy's month long Rim of the Pacific exercise, which ended in late July.

The project, which cost about $500,000, was paid for by the Navy and the National Oceanic and Atmospheric Administration and conducted by a team of about 15 researchers from government agencies and universities.

Working in small boats for three weeks, researchers tagged almost 40 whales with either a satellite tracking device or an archival tag, which records the sounds a whale hears and the depth and length of its dives.

About half the tagged animals were pilot whales. Other species included melon-headed whales, false killer whales and Blainville's beaked whales.

"This was the first time that we were ever able to tag these animals around realistic military exercises," said Brandon Southall, director of the ocean acoustics program for NOAA's fisheries division and a co-sponsor of the study.

It will likely take months to compile the data from the sensors so the whales' movements can be compared with detailed information on when and where the Navy ships were using sonar. Even then, Southall said, the data won't be conclusive. But it is a starting point, and he expects whale-tracking projects to coincide with Navy exercises in coming years.

Environmental groups have successfully sued the Navy to limit its use in the Pacific of midfrequency, active sonar - the technology warships depend on to detect enemy subs.

Studying deep-diving whales isn't just physically difficult. It also requires researchers to get special permits from the government and follow strict protocols to ensure that the mammals aren't harmed.

Last summer, NOAA began a three-year study of whales on a 600-square-mile instrumented Navy training range in the Bahamas. Researchers used the same technique - a long pole and suction cups - to attach archival tags to whales.

"It's harder than it would seem," said Southall, who did some of the tagging. "It's sort of an art."

The training range, outfitted with underwater hydrophones, allows scientists to plot out a single tagged whale's movement - after the fact.

The archival tags detach in less than a day and must be retrieved to access the recorded data. The information gives researchers "exquisite detail," Southall said, of a single animal over a short time.

In Hawaii, Southall said, the teams predominantly used satellite tags, which stay on for weeks. Satellite tags don't have to be retrieved, and they provide almost real-time information when a whale is on the surface.

The two tracking techniques complement each other, Southall said. But the biggest difference between the Bahamas and Hawaii experiments is the exposure to actual sonar.

In the Bahamas study, researchers used a recording of sonar, not the real thing.

The second phase of the Bahamas research begins later this month and runs through early October.

Southall said scientists and Navy brass want to know more.

"We both have common interests in getting a scientific explanation of what's really going on with this, and what we could learn that will help us manage the system better," he said.

Kate Wiltrout, (757) 446-2629, kate.wiltrout@pilotonline.com