Hundreds of dead fish discovered in American Falls Reservoir

The pursuing is simply a news merchandise and photos from Idaho Department of Fish and Game.

AMERICAN FALLS — On nan greeting of July 26, Idaho Department of Fish and Game fisheries biologists on pinch unit from nan Idaho Department of Environmental Quality (DEQ) responded to calls from nan nationalist regarding a imaginable “fish kill” successful American Falls Reservoir successful Power County.

Fish and Game Fisheries biologists study that astir 250 dormant rainbow trout could beryllium observed from nan shoreline extending southbound from nan vessel dock to nan dam, though it is difficult to estimate really galore full dormant food are coming successful nan reservoir.

Based connected h2o value tests conducted by nan DEQ, debased dissolved oxygen levels astir apt caused nan food deaths. On Tuesday, July 23, dissolved oxygen levels successful American Falls Reservoir measured astir 9 mg/L astatine nan aboveground and had dropped to 4 mg/L by Friday morning. The DEQ authorities modular for dissolved oxygen is 6 mg/L.

Why nan abrupt driblet successful dissolved oxygen levels? High winds (with a fewer gusts of 50 to 60 mph) from a Thursday evening large wind caused nan h2o successful nan reservoir to “turn over”, bringing nan h2o from nan reservoir’s bottommost to nan top. Large bodies of h2o for illustration American Falls Reservoir are stratified, meaning that location are chopped h2o layers varying successful somesthesia and dissolved oxygen levels. During nan summer, nan acold bottommost furniture of a ample h2o assemblage contains debased levels of dissolved oxygen, and if location is simply a abrupt turnover of nan h2o layers, that tin beryllium deadly for fish.

“The winds acted for illustration a elephantine spoon, mixing nan reservoir truthful to speak,” says Fish and Game Regional Fisheries Biologist Ryan Hillyard. “And, that mixing action brought stressfully-low levels of dissolved oxygen to immoderate parts of nan reservoir occupied by fish.”

Most of nan food affected by nan wind-generated turnover are rainbow trout, which is not astonishing to biologists.

“Trout are much delicate to debased dissolved oxygen levels than are different food type for illustration bass aliases perch,” says Hillyard. “Though we did spot a dormant bass while astatine nan reservoir, nan mostly of dormant food were trout.”

At 56,000 acres, American Falls Reservoir is Idaho’s largest reservoir erstwhile full. Events for illustration this person happened earlier astatine ample h2o bodies for illustration this 1 and though they tin beryllium alarming to anglers, nan food deaths that typically consequence are genuinely conscionable a mini driblet successful a very ample bucket. It is apt that astir food were capable to find refuge successful different areas of this ample reservoir, and impacts to nan fishery are apt not going to beryllium significant.