Noisy oceans takes toll on whales

More ocean noise from military sonar, shipping, and oil and gas exploration are threatening marine life, a new report from a U.S. environmental group says.

Dolphins and whales rely on sound to find food, avoid predators, interact socially and find mates.

The report by the Natural Resources Defence Council said the mammals can suffer long-term behavioural changes, hearing loss, bleeding, lesions and death from ocean noise.

The report follows up on a 1999 study of samples takes from beached whales suspected of being exposed to navy sonar.

"Military sonar has been linked to dozens of mass strandings of whales around the world, and oil-and-gas surveys have been shown to damage fish and dramatically reduce catch rates," the group said.

• FROM MAY 8, 2003: U.S. navy sonar blamed for whales' odd behaviour

Researchers suspect whales are suffering from a decompression sickness similar to "the bends" in humans.

It's thought that sonar may cause whales to surface too quickly or dive deeper where nitrogen bubbles form in the blood.

• FROM JUNE 9, 2003: U.S. navy under fire over sonar test

The group is suing the U.S. navy in the hopes of limiting use of sonar during training exercises.

The report's authors call for:

• Technological improvements to reduce sonic damage.
• Better monitoring.
• Stronger enforcement by the National Marine Fisheries Service.
• A commitment to international solutions.

A spokesperson for the U.S. Fisheries Service said the agency had not seen the report and could not comment on it.

No U.S. law or international treaty deals comprehensively with the problem, according to the environmental group.