Lack of "dissolved oxygen" leads to unprecedented fish die-off at Clear Lake

Image 1 of 7

Dead fish islands about the size of three football fields.

That’s how Mike Eagle and other Lake County residents are describing the unprecedented “fish kills” at Clear Lake, the largest natural freshwater lake in California just north of Napa County and San Francisco.

“This season is epic,” Eagle told KTVU. “We have dead fish year after year but nothing this crazy.”
This is true, according to Lake County Water Resources Invasive Species Coordinator Carolyn Ruttan. All summer, she has been fielding phone calls from residents, most of whom are terrified that Armageddon has come and that the water is not safe for drinking or swimming.

“I’m listening to phone calls every day about fish kills,” she said Wednesday. “Most people are telling me they’ve never seen anything like this.”

Although no one has formally counted,  there are literally hundreds, or perhaps thousands, of dead fish - including shad, crappie, catfish, carp, bass and sunfish - that have been found floating near the old Harbor Resort side of the lake on Soda Bay Road in Lakeport, for example. The fish are left on the shores and in the water to be eaten by birds and other fish.

The million dollar question is why: “The dissolved oxygen levels are drastically low,” Ruttan said.

What that means is that when the water heats up – as it has been all summer with weeks of triple-digit heat – the amount of “dissolved oxygen,” otherwise known as "depleted oxygen," the kind that easily passes through fish gills is greatly reduced, Ruttan explained.  And since the nights also have been so warm, the temperatures in the air and in the lake have not had a chance to recover – hence the major die-off, she said.
As to the heat, Ruttan said “90 percent of the scientists you talk to will say that climate change has something to do with this.”

Added community activist Claudia Konocti: There is no doubt that the tremendous amounts of fire retardant, ash, soot and run-off from the past several years of fires; pollutants, chemicals from illegal dumping and agricultural grows also play a major role in what's happening to the lake.

The die-off will largely subside, Ruttan said, when the weather cools down.

But until then, the images of the dead fish are sending Lakeport residents like Marge Tellez in a frenzy. Despite county alerts saying the water is safe for swimming and drinking, Tellez said she’s buying water to drink because the “lake is like thick green paint” and the smell can make you “almost vomit.”  She said what’s going on is “unacceptable” and she wants “answers and immediate action.”

Ruttan said in addition to the depleted oxygen levels, there is also an issue with the amount of cyanobacteria, or bluegreen algae, in the water. The lake has not been closed because of this algae, but Ruttan concedes that she personally swims with her mouth closed to avoid ingesting the water, showers upon getting out and won’t let her dogs go anywhere near the lakefront. As for drinking the water, Ruttan said that 16 municipalities all draw from the lake and that each agency treats the water to make it safe for drinking.

Ruttan is keenly aware that people are scared. And she encourages anyone with questions to give her a call.
“I know that people are wondering why this is happening,” she said. “About 99.9 percent of the phone calls I get start off with this terrifying language. And by the end, I’ve turned most of them around.”

For more information contact Carolyn Ruttan or Phil Moy at the Lake County Water Resources Department (707) 263-2344.