Undersea noise 'does harm whales'

By Alex Kirby
BBC News Online environment correspondent in Sorrento, Italy

The committee has urged for marine protected areas

Evidence that noise from human sources harms whales and other marine mammals is overwhelming, scientists say.

The International Whaling Commission, holding its annual meeting in Italy, says military sonar and oil and gas exploration are particular threats.

The numbers of beached whales found may seriously underestimate the numbers actually killed by sound.

They believe special protected areas could help to save marine mammals from being harmed in this way.

A report by the IWC's scientific committee says there is "compelling evidence" that entire populations of marine mammals are at potential risk from increasingly intense man-made underwater noise.

'Great concern'

The committee says in its report: "The weight of accumulated evidence now associates mid-frequency military sonar with atypical beaked whale mass strandings.

"The evidence is very convincing and appears overwhelming. Assessments of stranding events do not account for animals that are severely affected or died, but did not strand."

Earlier this month about 200 melon-headed whales headed into shallow water off the coast of Hawaii, with one dying, during US and Japanese naval exercises.

One possible cause under investigation is mid-frequency sonar. The report also expressed "great concern" over the impacts of oil and gas exploration on large whales.

It mentioned an incident in 2002 in which humpback whales were stranded off the coast of Brazil in unusual numbers during a submarine oil and gas survey that generated intense sound pulses.

Grey whale numbers are particularly low

The committee called for "strong, prompt action", especially for endangered whale populations like the western North Pacific grey whales. Only 100 animals, among them 23 females of reproductive age, are known to exist.

Global conservation campaign group the World Wildlife Fund has urged the Royal Dutch Shell energy group to suspend its Sakhalin oil project in the Russian Far East after the IWC called it a threat to the survival of the grey whales in the area.

The scientific committee urged investigation into setting up marine protected areas to keep marine mammals safe from underwater noise.

Last October, the US Natural Resources Defense Council said the US Navy had agreed to cut its use of a controversial low-frequency sonar system which could be harming marine mammals.

The journal Nature said the sonar signals might cause bubbles in the animals' tissue, in much the same way as divers can suffer decompression sickness known as "the bends".