Conservationists will continue to make legal challenges to protect the right whales and other marine mammals after the Navy won a renewed lease to train and test offshore, with few changes.

New restrictions put on the training by the National Oceanic and Atmospheric Administration add up to language that says the Navy will “minimize to the maximum extent possible” sonar when the rare whales are spotted, said Zak Smith, Natural Resources Defense Council attorney.

That joins an already in place reduction of decibels when whales are within 1,000 yards and a shut down within 200 yards.

Research has shown that sonar and explosion noises affect whales’ hearing at longer distances, Smith said, and that the deep-diving whales are detected only about 10 percent of the time. Whales communicate and navigate by echolocation.

Smith called the new rules a step in the right direction, but said more is needed for the whale and other species.

The five-year lease permits a sea and air warfare-training range along 50,000 square miles off the East Coast. Navy officials say the service has conducted training offshore for 60 years with little environmental impact, and has made changes when problems emerged.