SEATTLE (AP) - Researchers who track the endangered population of orcas that frequent Washington state waters say three whales are believed dead or missing since summer.

The Center for Whale Research said Friday that only 80 animals were accounted for during its July 1 census. Two females and a 10-month-old calf are missing.

Center senior scientist Ken Balcomb says the orcas, particularly mothers and babies, are struggling because they don't have enough food, a primary factor in their decline.

He and others say breaching four dams on the Lower Snake River is the best opportunity to save the orcas and restore runs of salmon that the killer whales eat.

The whales have a strong preference for Chinook salmon, which are typically larger and fatter fish, but those runs have been declining.