A federal judge banned the US Navy from using high-power sonar during a series of upcoming training exercises, ruling the technology can cause widespread damage to dozens of species of whales and marine mammals.
US District Judge Florence-Marie Cooper issued the temporary injunction on Monday in response to a Navy request to dismiss a lawsuit filed by the Natural Resources Defense Council.
The environmental advocacy group says the Navy planned to use mid-frequency sonar over thousands of square kilometers of ocean that can cause strandings and other harm to marine animals.
The training exercises are planned for the waters off Southern California, an area rich in marine life.
Joel Reynolds, a senior attorney for the council, said the injunction would force the Navy into compliance with federal environmental laws protecting marine life.
"We don't take issue with the Navy's judgment that it needs to use this technology," Reynolds said. "Our concern is when they test and train, they do so in a responsible manner."
The Navy said it has been closely monitoring marine life in Southern California's waters for 40 years and sonar has not harmed marine life.
Sonar technology is a vital tool in detecting submarines, it said.
Captain Neil May, assistant chief of staff for Third Fleet Training and Readiness, said the ban renders the Navy "partially blinded and deaf" in its search for underwater enemies.
"Our ability to train to the readiness standards and strengths using a critical tool has been put on the shelf," May said.
The Navy plans on running 14 training exercises using sonar.
It said it has already carried out three of these and has found no evidence of strandings, injuries or behavioral disturbance to marine mammals.