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How Heat Stresses Montana's Fish; And How Anglers Can Help

A.J. Coulter guides fly fishing trips on rivers all around Montana. Recently, he’s been starting his trips earlier in the day to avoid angling in heat of the day so as to not catch unhealthy fish.
Corin Cates-Carney
A.J. Coulter guides fly fishing trips on rivers all around Montana. Recently, he’s been starting his trips earlier in the day to avoid angling in heat of the day so as to not catch unhealthy fish. ";

Fish, and maybe you, are getting stressed out in this summer heat. But for fish, stress is made worse when, on top of trying to stay cool, they have to avoid eating a fly tied to a line.

In the heat wave of the past few weeks, guides and regulators have worked to protect fish during a time when fish are very vulnerable.

For A.J. Coulter, a guide of 20 years, anglers can still find ways to fish responsibly in low, warm waters.

As Coulter loaded up his guide boat near West Glacier around 7:30 this morning for a trip down the Middle Fork of the Flathead River, the air temperature was nearing the 60s.

"I guess you could look at us as bad guys for beating on the fish, but you know, the education we give people in the long run is probably better for the resource," Coulter says.

By 2:00 p.m. today the temperature was expected to rise to the 90s. That’s when one of the groups Coulter is guiding wanted to go fishing. He told them it would be better go early in the morning when the water is cooler and the fish are conformable.

"Nobody treasures the fish more than the guides," says Coulter.

When you think about it, fish can't escape their environment...So fish are pretty beholden to the actual temperature of its surroundings.

Still, Coulter has to balance his passion for fishing and the expectations of his clients, who spend big money to learn how to cast flies onto Montana’s rivers and streams.

He says his concern is for the long-term health of fish. In this heat, that means not fishing in the warmest parts of the day, being gentle with fish, and knowing how to catch and release safely; and if things get bad enough and rivers are running too low, not fishing at all.

"Hopefully mother nature steps in and helps fix things. You know, with maybe some rain. You know, maybe some cooler temps. But…I’ll just find another job…"

As of Friday, Montana Fish Wildlife and Parks placed what’s known as "hoot-owl" restrictions on the Blackfoot, Bitterroot and parts of the Clark Fork, and Flint and Silver Bow Creeks.

Those restrictions mean all fishing will close daily from 2:00 p.m. until midnight, continuing until conditions improve – meaning the water levels rise and temperatures drop.

At the confluence of the North and Middle Forks of the Flathead river, Montana Fish Wildlife and Parks’ John Fraley says the regulations protect fish as water temperatures rise.

"When you think about it, fish can't escape their environment," Fraley explains. "They’re not like a land animal that can use microhabitats that are different temperatures. The river is pretty homeothermic throughout, unless it's a really deep hole. So fish are pretty beholden to the actual temperature of its surroundings. So it is extremely sensitive to temperature. And we have an arm rule that the commission passed that gives FWP to limit fishing if you have three consecutive days where the high temperature of the water goes above 73 degrees."

As of now, no river in the Flathead has been placed under the hoot-owl restriction. But river levels are far below normal and water temperatures are climbing.

Fraley points to a graph of water temperatures in the Flathead River.

"Look at the water temperatures in the North Fork over the last 6-7 days; up, up, up, all the way up into the...above 66 degrees."

Fish found in Northwest Montana tend to be especially vulnerable to heat – the whitefish, the cutthroat and the bull trout.

"When trout are in water, or salmonids are in water that's above 70 degrees they begin to get stressed. 77 can even be lethal, to 80, is lethal to a fish. So once you get into the high 60s low 70s, the fish is stressed anyway and its whole system, its whole physiology doesn’t work well at those temperatures, so that’s why we're concerned. And that’s why even now it's a good idea for people, as we go into July, to fish more in the mornings and not 3:00 or 4:00 in the afternoon at peak temp times, or 5:00 when the fish are going to be more stressed."

Fraley says water levels on the Middle Fork and North Fork are a third of normal for this time of the year.

Fishing Guide A.J. Coulter says after guiding a morning boat, he’ll take a break in the afternoon when the water at its warmest, then head back on the river for a late evening trip. He says he tries to instruct his clients how to properly care for a fish once you catch it and plan on releasing it.

Catch and release, under usual situations has a 5-10 percent mortality rate. That goes up as water temperature rise.

"You know, the fish is tired because it has just exerted itself. So you can see its gill plates working harder to pump more O2 through its gills. So to facilitate that, you can move the fish back and forth to get more water flow, hence more oxygen into it. You can also release a fish in water that's more heavily oxygenated," Coulter suggests.

That would mean more active water, like rapids, rather than the hot, still water near a beach where the fish is more likely to die.

Ideally, a fish will not be taken out of the water, and hardly handled. Coulter teaches his clients these techniques.

Montana Fish Wildlife and Parks’ John Fraley says if temperatures continue to rise, hoot-owl restrictions could extend to rivers in the Flathead. He doesn’t ever remember that happening before.

Coulter prepares to meet his clients for the day, conscious to get on the river before it gets too warm.

"No one is going to give the fish more TLC than a guide," Coulter insists.

Corin Cates-Carney: TLC?

Coulter: Tender love and care.

This year, TLC includes knowing that some days, guides and anglers might have to give fish little more distance, even though it's their passion and job to do exactly the opposite.

Corin Cates-Carney manages MTPR’s daily and long-term news projects. After spending more than five years living and reporting across Western and Central Montana, he became news director in early 2020.
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