A U.S. federal appeals court has ordered the Navy to reduce the use of its towed array sensor system as it harms marine mammals.
The Ninth U.S. Circuit Court of Appeals in California found that a 2012 district court decision which allowed the navy to use low-frequency sonar for training, testing, and operations was not in accordance with the Marine Mammal Protection Act.
Whales, dolphins, walruses, and other marine mammals rely on perceptions of underwater sound for vital biological functions such as catching prey, navigating, and communicating. These sounds are interrupted LFA sonar vessels the navy uses to hunt quiet foreign submarines.
Apart from disrupting hearing, these sonars can cause physical injury at sound levels greater than 180 dB. Exposures below 180 dB cause changes in the natural behavior patterns of the affected animals which can cause them to stop communicating with each other, to separate from their calves or to stop mating.
The ruling from 2012 permitted the navy to use sonars but required it to stop or postpone sonar use if marine mammals were sighted near ships.
In 2012, environmental groups, led by the Natural Resources Defense Council, filed a lawsuit claiming that the approval violated the Marine Mammal Protection Act.
The Court of Appeals has now reversed the decision and remanded the matter to the district court for further proceedings.