ABOARD THE USS HOWARD — Two months after training under one set of sonar rules off California, the destroyer Howard operated yesterday under a separate set of rules off Hawai'i.

The need to change procedures reflects federal court rulings in both locations pertaining to the effects of sonar on marine mammals such as whales and dolphins, and an increasing hardship the Navy says it faces as it trains for anti-submarine warfare.

The USS Ronald Reagan aircraft carrier strike group is conducting anti-submarine warfare training through the weekend as it heads to the western Pacific and possible duty in the Persian Gulf. The strike group, in addition to the carrier Reagan, includes three destroyers, a cruiser, and a frigate.

Rear Adm. James P. "Phil" Wisecup, commander of the strike group, said the changing sonar rules "just complicate things" in a warfare area that's already very complex.

"In the end, just give me a standard, and I can meet it," he said.

As a result of federal court decisions in California, the Navy must shut down sonar when marine mammals are within 6,600 feet. For anti-submarine warfare training off Hawai'i, sonar must be shut down when mammals are within 5,000 feet.

Off the southern coast of California, the Navy said it must post three watchstanders and two National Marine Fisheries Service lookouts. Off Hawai'i, the Navy has to have three dedicated marine mammal lookouts in addition to at least three watchstanders on the bridge team.

The Ronald Reagan is the third carrier strike group to train in anti-submarine warfare off Hawai'i this year in what is the Navy's No. 1 warfighting priority in the Pacific.

The use of midfrequency Navy sonar was determined to be a "plausible, if not likely" contributing factor to the mass stranding of up to 200 melon-headed whales in Hanalei Bay during Rim of the Pacific naval exercises in 2004.