Dead rainbow trout are floating on the surface of Treasureton Reservoir where the ice has receded.

Low oxygen conditions in the reservoir north of Preston have led to a winter fish kill. A series of factors contribute to fish kills like this one. The plant decomposition under the ice uses oxygen. Oxygen can be replaced by photosynthesis, a process by which plants make food, but light is required for this process. Layers of ice and deep snow can block light from reaching the plants. When that happens, photosynthesis stops and oxygen levels in the reservoir cannot be replenished.

The bottom line is that the fish in Treasureton Reservoir are dying from a lack of oxygen.

"Shallow reservoirs with abundant vegetation are most susceptible to winter fish kills," said Dave Teuscher, fisheries biologist for the southeast region of the Idaho Department of Fish and Game. "When prolonged ice cover and snow are added to the scenario, the chances for oxygen problems are greatly increased."

Fish and Game can't tell yet whether the fish kill will affect anglers on Treasureton this summer. As soon as the reservoir opens up, Fish and Game will survey the water and determine how significant the fish kill was.

Once armed with this information, Fish and Game will then be able to adjust the fish stocking plan for the reservoir this year. Fish and Game will release additional information about Treasureton Reservoir and the status of the fishery as soon as it is available.