Whales and ships are both becoming more common in the Bering Strait near Alaska, prompting concern among environmentalists, who are fearing for the safety of the marine mammals. 

Some members of whale species that normally live in the sub-Arctic are moving toward Arctic regions as ice begins to clear. Researchers spent three years listening to whales in the Bering Strait, using underwater microphones. The program, which recorded the marine mammals during the summer and early winters of 2009 to 2012, was a cooperative effort of American and Russian naturalists. 

These recordings reveal a growing population of whales coming into the frigid waterway. Whales found in the waters between Russia and Alaska include Arctic belugas, sub-Arctic humpbacks, bowheads, fins and killer whales. 

Oceanographer Kate Stafford, of the University of Washington, will present the finds at the Ocean Sciences meeting Hawaii on 26 February. She said she expected to find an increasing population of whales near the waterway. 

"It's not particularly surprising to those of us who work up in the Arctic. The Arctic seas are changing. We are seeing and hearing more species, farther north, more often. And that's a trend that is going to continue," Stafford said. 

Bowheads and belugas use the waterway to head south for winter, from their homes in the Arctic. Meanwhile, fin, killer and humpback whales travel north from sub-Arctic regions, in order to feast on the great diversity of life in the Chukchi Sea. 

Stafford and her team believe the whales may be taking advantage of the water newly-opened to them by melting ice.  

What concerns researchers the most is these travel patterns pass through two busy shipping lanes. This could cause danger to both whales and ships in the event of a collision. Although it is 58 miles across, the Bering Strait is just 160 feet deep. As well as the danger of impacts, the noise of the ships could make it difficult for the animals to communicate. 

"Marine mammals rely primarily on sound to navigate, to find food and to find mates. Sound is their modality. If we increase the ambient sound level, it has the potential to reduce the communication range of cetaceans and all marine mammals" Stafford said.

The songs of the humpback were heard until late in autumn, while killer and fin whales were recorded into the first half of November. 

In the conclusions of the study, Stafford and her team recommended slower ship speeds through the Bering Strait as a way to reduce the possibility of dangerous collisions. Reducing engine noise could also assist the animals in navigation and communication, researchers stated.