A warm July day for campers and swimmers at Niskonlith Lake was interrupted by dozens of dead fish washed up on the shore and floating in the shallows.

On July 6 Richelle Marie was one of several campers and picnickers at the lake near Chase who noticed the dead fish. She said a dead beaver was floating in the lake as well. She asked a park ranger about the state of the lake and they said fisheries authorities had been notified and would investigate.

Doing some of her own investigation into the bizarre phenomenon, Marie heard from a conservation officer that the deaths of the fish could be related to lake turnover. The turnover is a process caused by the seasonal change in water temperature. According to natural geographic the density of the water changes along with its temperature and so layers of lake water can move to different depths.

Most of the dead fish along the shore of the lake appeared to be kokanee salmon, a species known for their sensitivity to changes in water temperature. According to bcfishn.com, the fish, which are a common target for anglers, spend the warmer months of the year at depths where the warmer surface water and colder water below meet. Disruption in temperature at those depths can be harmful or even lethal to the kokanee, particularly when the water climbs above approximately 12.8C.

A Department of Fisheries and Oceans representative presented another possible explanation for the dead fish: an oxygen depletion issue. According to the United States Geological Survey, the concentration of dissolved oxygen in water is inversely related to water temperature. Bacteria in water can also consume oxygen.

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