Orcas, one of the world's most powerful predators, dread the drone from ship engines and propellers. The underwater noise, which can be intense, interferes with the way that these killer whales and other marine mammals communicate and feed, researchers have found.

Increasing ship traffic is raising the level of underwater pollution and threatening a range of endangered marine species.

"The good news is that by reducing speed, even by as little as one knot, tankers and container ships can cut noise levels and help save numerous threatened species," said marine biologist and lead researcher Dr Scott Veirs, of the Beam Reach Marine Science and Sustainability School in Seattle.

"Ship noise can interfere with the killer whale's ability to catch salmon, their favourite prey, in the murky waters of the Pacific Ocean near Seattle," he explained.