A Plague on the Klamath River

Nearly one year ago, Mike Belchik, a senior biologist for the Yurok Tribe, was overseeing an emergency laboratory on a remote gravel bar in the Klamath River on the tribe's Northern California reservation. That morning, crews had netted two dozen salmon from a 20-mile stretch of the lower river. Now they were inspecting their catch for a parasite dubbed "the Ebola of Klamath salmon." Working quickly, the men snipped a layer of glistening gill tissue from each fish and slid it under a microscope. The parasite—a protozoan named Ichthyophthirius multifiliis, or simply Ich—is salt-colored and less than a millimeter wide, with a fringe of madly fluttering hairs. Belchik and his crew had monitored for it all summer, but only that weekend had infected fish begun appearing in their nets. In 2002, Ich killed some 70,000 king salmon in the Klamath—the largest such die-off ever recorded on the West Coast. Afterward, the parasite population declined below detection, but it is native to the river, and there was reason to fear its resurgence. Last September, California was already three years into perhaps its worst drought in more than a millennium, and the Klamath was low and warm. In slow water thick with fish, Ich can reproduce rapidly. Thousands might feast on a single salmon. Once engorged with blood, they drop off and anchor to the river bottom. Then each one bursts open, releasing up to 1,000 offspring. The cycle can take as little as a week. "It felt like a catastrophe was looming," Belchik says. The Yurok crews were trying to determine whether water should be released from reservoirs upstream in an attempt to disrupt the parasite's life cycle...more