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Heat and drought causing concern for Idaho's coldwater fish populations

Posted at 4:11 PM, Jul 08, 2021
and last updated 2021-07-08 18:20:09-04

IDAHO — With excessive heat warnings, drought conditions, and significant wildfire potential it's shaping up to be a challenging summer for many reasons; one of those being heat stress in Idaho's cold-water fish species.

Excessive heat raises the water temperature and as a result, there's not enough oxygen in the water for fish to survive, a concerning thing for cold-water fish species like trout.

“So far, knock-on-wood, we haven't had any significant fish kills in the Southwest Region," John Cassinelli, Idaho Fish and Game Regional Fisheries Manager, SW Region, said. "We have had some reports of small fish killed in varies places where temperatures have gotten warm in the heat of the day.”

The concerning part for IDFG is how early in the summer they're seeing warmer water temperatures.

“We deal with this pretty regularly in mid to late July and into August each year, but for it to be already happening in mid-June to early July it could be a long hot summer, and those effects are cumulative," Cassinelli said. "We may see more issues later in the summer than they normally would.”

The biggest focus of concern right now is reservoirs.

“In a dry year like this most of the reservoirs are serving the purpose of irrigation water," Cassinelli said. "We draw those down throughout the summer for irrigation water and those water levels drop and temperatures rise and you potentially start to run into issues with warm water with low oxygen levels.”

When water does become too warm or oxygen levels too low, IDFG has to make a decision.

“We can go in and move those fish physically to different water. That typically involves us using nets or electrofishing and going in and catching as many of those live fish as we can and transporting them to a more suitable water body and releasing them,” Cassinelli said.

“The other thing that we will do is issue a salvage order that basically removes the limits and gear restrictions from a given water body so anglers can basically go catch as many fish as they’d like and taking them home," Cassinelli said. "They're putting them to use rather than them dying in the environment.”

Something they've already done in the Magic Valley at Magic, Mormon, and Fish Creek Reservoirs.

But, as concerning as this summer is, John says it's important to note how resilient fish are.

"Just know that if you have a favorite reservoir that has a fish kill, that it is not gone forever. We can reintroduce fish to those water and turn those fisheries around and bring them back."

IDFG is asking anglers and sportsmen to report any large amounts of dead fish they see, so they can take action as soon as possible.

Their regional headquarters phone number is (208) 334-3700.

They also want anglers to be mindful of not doing catch and release in warmer bodies of water because of the extra stress on top of heat stress that it's putting on the fish. You can read more about this by clicking here.