California's thirst is helping drive an endangered population of West Coast killer whales toward extinction, federal biologists have concluded.

The southern resident killer whale population, which numbers 83, spends much of its time in Puget Sound but since 2000 many of them have been spotted off the California coast as far south as Monterey Bay.

In a draft scientific report, biologists conclude the damage that water operations are doing to California's salmon populations is enough to threaten the orcas' existence because the water mammals depend on salmon for food. Federal officials confirmed the conclusions of the report to MediaNews on Friday; the data have not been released.

"It does point to the interconnected nature (of problems in the Delta)," said Maria Rea, the Sacramento area office supervisor for the National Marine Fisheries Service.

The findings, contained in a draft report by the agency's scientists, could elevate public support for environmental protection in the Delta, where the conflict between environmental advocates and water users has centered on Delta smelt, a nondescript fish that grows a couple of inches long and smells like cucumbers.