Environmentalists insist the Navy needs to do more to protect whales and other marine mammals, even after the activists forced limits on the military's use of sonar in maritime exercises off Hawai'i last month.

But the Navy is adamant that it won't allow the agreed restrictions on mid-frequency active sonar to set a precedent. It says the steps were often unnecessary, hindered training and in some cases weren't based on fact.

"There is no science that supports some of the limits we're being driven to," said Adm. Gary Roughead, Pacific Fleet commander. "I believe it is important that we introduce science into this argument."

The perception gap sets the stage for further legal and public relations battles as the Navy, for the first time, prepares to seek federal permits to use sonar during all of its anti-submarine warfare exercises starting in January.

Sailors use active sonar by pumping sound waves through the ocean and listening to the echo as it bounces off underwater objects. It's a key technology for finding enemy submarines, and Navy leaders have made practicing sonar techniques a top priority.

Research on how sonar affects marine mammals is still relatively limited, sparking disputes about what might harm the animals and what the Navy should do to protect them.

But scientists say sonar may mask the echoes some whales and dolphins listen for when they use their own natural sonar to locate food. Navy sonar may also startle some species, in particular beaked whales, prompting them to rush to the surface.

There's evidence that this gives them a form of "bends," the decompression sickness human divers get when they surface too fast.

MILITARY SAFEGUARDS

There are steps the Navy took to protect ocean dwellers during its Hawai'i "Rim of the Pacific" drills — the world's largest international maritime exercises involving about 40 ships — that it is willing to take again.

In fact, the Navy devised some of the procedures itself in consultation with the National Marine Fisheries Service amid evidence its sonar contributed to the death and mass stranding of marine mammals in the Bahamas in 2000.

Rear Adm. James Symonds, Navy director of environmental readiness, said he believes having sailors watch through high-powered binoculars for whales and dolphins can help keep marine mammals from harm.

He further agrees that ships should turn down their sonar when marine mammals are spotted nearby because some animals may be injured — or compelled to swim away — when they come within 450 yards or so of active sonar.

The Navy is less likely to object to such steps as it seeks permits to use sonar in sub-hunting exercises scheduled for January.

However, there are other measures the Navy took — such as aerial and boat surveys of areas before and after sonar exercises — that Symonds said were cumbersome and didn't do much to protect whales.

For the longer term, the Navy hopes to win a blanket "letter of authorization" from the National Marine Fisheries Service, the federal regulator in this case, to use sonar in exercises in a given geographic area. These would cover regions such as the waters around Hawai'i, off Southern California and off the Pacific Northwest.

OPPOSITION READY

To win this permission, which would be good for five years, the Navy will complete environmental impact statement studies for each area, Symonds said.

The Navy hopes to have authorization for Hawai'i by the next Rim of the Pacific exercises in 2008.

Symonds couldn't predict what measures the Navy would adopt in the future.

"It comes down to, what is the science, what does the regulator believe, what's the regulator's responsibility to protect the environment, and how is the regulator going to react in the absence of science?" he said.

The Natural Resources Defense Council, which is leading the legal fight against the Navy, has vowed to push the military to do the maximum.

Joel Reynolds, the organization's senior attorney, said the measures the Navy agreed to for the Hawai'i exercises offered good examples of "common-sense measures" that protect marine mammals. But he said the Navy needs to strengthen its steps and adopt additional ones, not roll back those already tried.

"The Navy continues to drag its feet. It wants to do less. It needs to do more," said Reynolds.

The council plans to seek further concessions from the Navy through a lawsuit it has already filed in federal court challenging the Navy's use of mid-frequency active sonar, Reynolds said.

The group has filed another lawsuit against low-frequency active sonar, a newer technology under development that sends sound waves across greater distances.

The Navy hopes this sonar, which is operationally available on only two of its ships, will allow it to spot enemy submarines even when they are far away. Environmentalists view low-frequency sonar as an even graver danger to marine mammals because it sends sound over greater expanses of the sea.