PORTOLA, Calif.- California wildlife officials dumped 16,000 gallons of a fish poison into a northern Sierra reservoir to kill off the invasive northern pike.

The poison was poured into Lake Davis early Tuesday and thousands of fish were dead by the afternoon, the San Francisco Chronicle reported.

The northern pike isn't the only fish dying, the newspaper said. By the end of the week, all of the lake's famous rainbow trout, many catfish, shiners and other bait fish also will be dead.

The northern pike, introduced illegally in 1994, had taken over the lake and devastated the trout population that fuels the local tourism industry.

Fish and game officials were afraid the pike would escape into the Sacramento-San Joaquin River Delta and destroy the salmon and steelhead populations, the newspaper said.