A Canadian Navy frigate used sonar in the enclosed waters of Juan de Fuca Strait this week, but marine mammals were not endangered, the ship's commanding officer said.

Cmdr. Scott Van Will, commanding officer of HMCS Ottawa, said checks ensured no marine mammals were in the area before low-frequency sonar was used as part of an anti-submarine warfare exercise.

"We have procedures in place. The marine mammal mitigation policy started in 2008 and that pretty much orders me to take some specific steps," Van Will said.

That includes visual and sound checks that pick up everything from whales to porpoises within a 3,660-metre range, he said. "I have faith no marine mammals were in the area at that time."

But whale monitoring and environmental groups say sonar should never be used in the area designated by the U.S. and Canada as critical habitat for endangered southern resident killer whales. The Natural Resources Defense Council is asking the U.S. government to talk to Canada about halting all naval sonar use in the Salish Sea.

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