Are Montana fish in hot water?

Drought and heat are stressing trout

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With hot summer weather heating up Montana’s rivers and streams, Montana Trout Unlimited is urging fishermen to give trout a break.

In response to the drought-like conditions, Montana Fish, Wildlife and Parks issued mandatory fishing restrictions in late July to the coolest parts of the day on the Big Hole, Bitterroot, Clark Fork, Dearborn, Madison, Jefferson, Sun and Smith rivers.

But MTU would like anglers to voluntarily go beyond the mandatory restrictions and consider fishing in higher elevation streams and mountain lakes — maybe not even fish at all.

“When streamflows and temperatures become very acute, consider doing something else,” MTU advises. “Montana has no shortage of alternative outdoor activities.”

Trout thrive in cold clean water, MTU conservation director Mark Aagenes points out, and high summer temperatures can force trout into survival mode.

“Under these conditions, trout have enough to contend with without the added stress of being caught and handled,” Aagenes said.

According to MTU, salmonids, which include trout, prefer water temperatures from 54 to 63 degrees, although some trout have adapted over many generations to higher water temperatures.

Sudden temperature increases can result in a fish kill, but generally higher temperatures compound other stressors fish are already facing, including reduced dissolved-oxygen levels in hotter water.

Water temperatures in many of Montana’s popular trout streams have reached the upper 60s, MTU said, and some have reached the 70 degree mark. A complete list of FWP’s mandatory restrictions can be found online at http://fwp.mt.gov/news/drought/waterClosure.html.

Montana’s streams are not the only water bodies affected by the drought and heat. In his annual State Of The Lake address to the Flathead Lakers on July 30, Flathead Lake Biological Station director Jack Stanford said water temperatures in Flathead Lake could reach their highest recorded level this summer.

While water clarity in the lake remains good this year, the higher temperatures could create conditions that algae thrive in, he said. Research data shows no current trend supporting algae growth, but nitrogen levels in the lake are increasing, he said.

Flathead Lake is in a “very delicate balance,” Stanford pointed out, and it wouldn’t take much additional nitrogen and phosphorus from runoff entering the lake to tip the balance.

Stanford said a modeling effort by the U.S. Environmental Protection Agency using data from the Flathead Lake Biological Station could provide useful information on the nutrient-loading process. He said he’s encouraging the Northwest Power and Conservation Council and the Bonneville Power Administration to provide money for the modeling.