Seven orcas have disappeared from Washington's Puget Sound, and experts fear they have died, victims of a declining population of Chinook salmon.

The orcas, or killer whales, have not been seen in almost a year, The Seattle Times reported Saturday. They included the oldest and youngest animals in the Puget Sound population, as well as two females in their reproductive prime.

If the orcas have died, the population in the sound is now 83, down from a recent high of 97 in 1996. Environmentalists say the orcas are threatened by the drop in salmon numbers and by noisy boat traffic that interferes with their ability to use echo-location to find food.

"Orcas don't exist in a cafeteria somewhere; they depend on the overall bounty of the natural world," said Howard Garrett of Orca Network. "Protecting Puget Sound equals saving salmon, which equals saving orcas."