Killer whale in the Salish Sea (c) Jane Cogan
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The killer whales struggling to find fish

A team from the Center for Whale Research in Washington State has been tracking the lives of killer whales off America's North Pacific coast since 1976.

After being decimated by the captive orca industry more than 40 years ago, the population has now recovered but is facing new threats.

Ken Balcomb and Deborah Giles from the Center for Whale Research on San Juan Island, explain.

Video by Victoria Gill and David Cheeseman