OROVILLE – The most likely cause of the many dead fish reported in Lake Osoyoos is due to the high water temperatures, according to the state Department of Fish and Wildlife.

Several people have reported the dead fish, many of which are sockeye salmon returning to the area to spawn. Ford Waterstrat with the Lake Osoyoos Association contacted Fish and Wildlife and has relayed their responses to LOA members.

“I spoke with our Fish Pathologist, Bob Rogers this morning and he thinks the likely culprit is Columnaris, a very common cold- and warm-water fish pathogen of fishes worldwide,” said Waterstrat last week. “We’ve seen it before in Lake Osoyoos. The high temperatures in the lake and the Okanogan River put more stress on fish that prefer cooler water, making them more susceptible to infection.”

To check for Columnaris, you look under the operculum (the bony plate covering the gills) – the gills will either be eroded away or, be a daffodil yellow color, according to Rogers.

“The number of fish affected may seem high, but with over 300,000 sockeye making it to Osoyoos, hopefully a large proportion of them are able to continue on to their natal spawning grounds,” added Rogers, who came up to Oroville last week and confirmed the cause of the fish kill was Columnaris.

According to Wikipedia, “Columnaris is a symptom of disease in fish which results from an infection caused by the Gram-negative, aerobic, rod-shaped bacterium Flavobacterium columnare.” The fish disease poses no risk to humans.

“Given the high temps, 77 degrees Fahrenheit, I might expect losses from several common opportunistic bacterial diseases, or simply losses to low oxygen levels,” said Constance Iten, Area Habitat Biologist, with Fish and Wildlife. “At 77F, oxygen saturation is approximately 8.3 parts per million at 1000 feet above sea level. As oxygen levels approach those values at those temps it becomes quite stressful.”

Bearing out the high temperature theory, was a call to the G-T office from a woman who lives on the lake and said sockeye were gathering around a stream outlet into the lake and that they trying to swim up the outlet pipe which was releasing cooler water. She also reported that the seagulls seemed to be getting their fill of the dieing and dead fish.

The Lake Osoyoos Association says their mission is to “promote and encourage understanding and management of the lake, watershed and ecosystem of Lake Osoyoos.”