EUREKA (CBS/AP) — The month-long Trinity River dam water releases that ended on Sept. 20 have helped prevent disease and parasite outbreaks on Chinook salmon and other fish harboring on the drought-stricken lower Klamath River, officials said.

The flows down the Trinity River and into the lower Klamath River helped cool the drought-stricken waters, improving fish immune systems and washing away deadly, single-celled parasites known as ich that thrive in low-flowing, warm waters.

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Nearly 51,000 acre-feet of water was released from Lewiston Dam on the Trinity River between August and September.

Senior fisheries biologist Mike Belchik of the Yurok Tribe says a survey of 25 fish conducted last week by him and his crew at Tectah Creek on the lower Klamath River found only two fish to have contracted ich, and those infections were minor.

Between early July and Monday, Belchik said 25 percent of the fish the tribe surveyed on the lower Klamath River were infected by ich at varying severities.

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“The ich continues to surprise us,” he said. “But right now I have more confidence than I’ve had at any point in the year.”

This is the second time that ich has been detected on lower Klamath River fish since the 2002 outbreak that led to one of the most catastrophic fish kills ever to have occurred on the system. The first detection of ich since 2002 occurred between mid-September and early October was last year when 80 percent of the fish the Yurok Tribe sampled on the lower Klamath River were found to be infected with the parasite.

Stillwater Sciences senior fish biologist Joshua Strange said that they are not seeing any increase in parasite infection as fish move upriver from the lower Klamath River into the Trinity or main stem Klamath rivers.

“We’re pretty much in the safe zone at this point for the year,” he said. “We don’t think there is really any risk for any type of severe outbreaks or die-offs at this point.”

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Dam releases to the lower Klamath River had also occurred last year. However, fish were still becoming infected — some quite severely — at the end of September and early October 2014. Belchik said this year’s dam releases seem to have led to the opposite outcome.