Environmental organizations sued in federal court yesterday to block the Navy from planned exercises using high-volume sonar in Hawaiian waters.

The high-intensity, mid-frequency sonar has the potential to damage several endangered species that frequent Hawaiian waters, including marine mammals such as Hawaiian monk seals and whales, said Paul Achitoff, attorney with Earthjustice.

He said the proposed tests would occur within or near both the Hawaiian Islands Humpback Whale National Marine Sanctuary and the Papahanaumoku'akea Marine National Monument. He said the Navy has not tried to schedule its training to avoid the season when humpback whale mothers and calves are in Hawaiian waters.

The law firm in the suit represents Ocean Mammal Institute, Animal Welfare Institute, Surfrider Foundation, Center for Biological Diversity and Kahea — the Hawaiian Environmental Alliance.

Navy ships use mid-frequency active sonar to detect silent diesel submarines. The Navy said it has already conducted two such training exercises in Hawaiian waters this year, without any adverse effects on marine life.

"The Navy takes its environmental responsibilities very seriously. We live on the world's oceans and have high regard for that precious resource. The Navy also has a responsibility to train the sons and daughters of America who may be called upon to go in harm's way," said Jon Yoshishige, Navy Pearl Harbor-based public affairs officer.

"We go to great lengths to minimize any potential effects on marine life through the use of protective measures, and make every effort to safeguard marine mammals when exercises are conducted," he said. The training is critical to the readiness of the U.S. fleet, he said.

Achitoff said the Navy in the past has agreed to a range of procedures that reduce the potential harm to marine life. He called it "bewildering" that the service has abandoned those measures.

But Yoshishige said the fleet has consulted with the National Marine Fisheries Service and is meeting legal requirements.

"We are complying with all applicable laws and regulations, including the requirements of the Endangered Species Act with regard to mitigation and monitoring as a result of coordination and consultations with the National Marine Fisheries Service. These measures were designed to protect all marine mammals in the Hawaiian Islands," he said.

But Achitoff argued that the Navy has failed to deal with significant known impacts of sonar.

"There is no scientific doubt that intense acoustic energy from Navy sonar can kill, injure or significantly alter the behavior of whales and dolphins," he said in the complaint, citing mass strandings and physical injuries to cetaceans after sonar exercises.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.