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Dead fish

BoatIt doesn't compare to the number of fish that died there last year, but Thursday morning a Community Services District crew was on Laguna Joaquin picking up dozens of dead fish. Click photos for larger images.

Dozens of dead fish were skimmed from Laguna Joaquin Thursday in a lesser version – possibly with a different cause – of the fish die-off that occurred there 13 months ago.

The Community Services District, which is responsible for the lake’s water quality, addressed the die-off in an announcement Thursday afternoon, saying it had measured dissolved oxygen at the lake and found levels too low for fish to survive.

Two CSD workers spent the morning on the lake, scooping up dozens of fish, most of them 6 inches long or less, most of them bass and a few bluegill, the CSD reported.

To resolve the problem, the CSD said it was working with the Rancho Murieta Association to run compressors with air lines into the basin to help bring up oxygen levels. Also, the RMA will run its lake fountains around the clock to try to help the situation, the CSD said.

As for what caused the oxygen problem, the CSD echoed a theory offered by Larry Shelton, a retired environmental scientist who lives on the lake and has fought for different approaches to managing it.

Shelton said he believes the dead fish – which he numbered at about 150 – were killed by environmental factors, unlike last year’s incident, which was blamed on chemical treatment. He thinks the algae that had colored the lake a vivid green in recent weeks was killed by recent cooler temperatures, and the death process of algae consumes a lot of oxygen from a body of water.

Disagreeing with the CSD statement, Shelton said he had taken readings for dissolved oxygen at the lake and found acceptable, if not great, numbers.

Shelton plays an active role in management of the lake with the CSD and at RMA, where he is a director.

As for other possible factors, county Vector Control added several thousand mosquito fish to the lake in the last three weeks, Shelton said, and did a “major treatment” for mosquitoes. In August, CSD did a treatment with liquid Bti to address midge flies, he said. Bti – short for Bacillus thuringiensis israelensis – is a naturally occurring bacteria found in soils. It’s used across the country for mosquito control and doesn’t harm fish.

Shelton believes his algae theory and offers this bottom line for the die-off: “We think it was a one-time thing.”

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