Fish winter kill at Mormon Reservoir

FAIRFIELD - A combination of thick ice, deep snow, and low storage conditions likely caused a fish winterkill at Mormon Reservoir.

“Winterkills occur when sunlight is blocked for extended periods limiting photosynthesis which provides oxygen in the water,” said Doug Megargle, Regional Fishery Manager. “Decomposing bacteria use up the available oxygen to break down vegetation leaving none for other aquatic organism, like fish.”

Investigations are ongoing and Idaho Department of Fish and Game has not determined if it is a complete or partial winterkill.

“This is very disappointing,” said Megargle. “Camas County had worked hard to restore public access to the fishery last year rebuilding bridges that had been condemned for safety reasons.

“We had stocked last fall hoping we could begin to rebuild the fishery, even though stocking conditions weren’t ideal. We took the chance stocking in better than average water levels for that time of the year, but we did not anticipating such a heavy snowfall winter”.

Idaho Fish and Game will start over trying to rebuild the fishery this spring. Water storage will likely be substantially improved in 2017 due to the same snowpack that caused the winterkill.

Approximately 3,000 12-inch long trout are scheduled to be stocked in late April, and 100,000 fingerling-sized trout will arrive in September, should conditions be suitable.