Navy defends sonar amid fight over whale safety

By Kristin Roberts

ABOARD THE USS MOMSEN (Reuters) - "Pod of whales bearing zero-zero-zero, range 2,000 meters," a U.S. sailor shouts to his commander, warning whales have moved in front of the ship as it hunts a submarine off the California coast.

Within minutes, the whales have moved to within 200 meters (yards) of the ship, forcing its commander to turn off the active sonar being used to search for a sub that has eluded the USS Momsen and other ships for three days during a training exercise.

Below deck, the regular ping of the sub-hunting sonar -- which environmental groups claim hurts and even kills whales -- goes quiet and four seamen ease back in their chairs.

They've spent hours staring in the dark at green digital lines zigzagging down computer screens, looking for patches of more intense color that could indicate a sub.

"My concern is, I want to get away from the whale but I want to maintain contact with that submarine," said Cmdr. Michael Sparks, commander of the destroyer.

In this case, he could not do both.

In a real-life scenario, the Navy would keep the active sonar on if it were searching for a sub, particularly the type of quiet submarine it says potential adversaries might use in shallow coastal waters. Navy officials say Iran, for example, could use these diesel-electric subs to try to disrupt oil flows through the Strait of Hormuz, which handles 17 million barrels per day or two-fifths of the world's traded oil.

But in training, worries about the impact of sonar blasts on marine mammals have led the military to impose rules that force ships to first reduce the power of their active sonar and then halt it altogether as whales approach.