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Underwater noise has been identified as a key threat to at-risk whales.

A listening station that could help researchers assess the impact of marine noise on orcas has been lowered into the Strait of Georgia.

Tom Dakin, sensor technology development officer at the University of Victoria's Ocean Networks Canada, said the station was successfully placed on Monday from the exploration vessel Nautilus.

Mr. Dakin, in a phone interview on Tuesday from on board the ship, said the station will allow researchers to monitor every large vessel that goes into Port Metro Vancouver.

"We can get a noise level from that vessel across all of the different frequencies. From that, we can assess just how much of an impact that particular vessel has on the hearing capabilities of the orcas," he said.

Mr. Dakin said marine noise can negatively affect orcas in several ways. For one thing, the noise can make it difficult for orcas to communicate and increase the likelihood a pod will get split up, he said.

Marine noise can also make it difficult for orcas to track down food, he added.

"They use echolocation primarily to hunt chinook salmon. That's the main portion of their diet. With the shipping noise around, if it masks those echolocation signals for the whales, then the whale can't find its food any more and that's pretty disastrous," he said.

Although the project will look closely at ships hauling cargo, Mr. Dakin said other noise could also be found to have an impact.

"The whale-watching fleet is much closer to the whales than the cargo ships tend to be. The closer you are, the louder the sound, so that could be a problem. There's a lot of recreational boats out here in the Strait of Georgia, so those power boats could be a problem as well," he said.

He added that fishing boats and B.C. Ferries vessels could also be a factor.

Ocean Networks Canada's partners for the project include Port Metro Vancouver and JASCO Applied Sciences. The listening station is under the Strait of Georgia's inbound shipping lane, and information from it is already being relayed to the University of Victoria, Mr. Dakin said. The listening station equipment will be replaced after two years.

Carrie Brown, director of environmental programs at Port Metro Vancouver, in an interview said the project is part of its efforts to develop measures that will reduce potential threats to whales as a result of shipping. The program formally came into effect last November, although this project has been in the works for a couple of years.

The initial data assessment phase is expected to run between six and nine months, Ms. Brown said.

"For southern resident killer whales, they use sound to communicate, to find prey, it's part of their socialization. So when you have underwater noise, it can really mask their ability to hear each other, as well as impact their ability to find their prey. It's like you and I going into a bar and not being able to hear anything," she said.

Ms. Brown said the program as a whole focuses on four key areas that may affect marine mammals: underwater noise, physical disturbance such as direct strikes from vessels, environmental contaminants, and availability of prey.