Brian Upesleja casts toward the bank of the Hoback River as Luke Smith rows during an excursion July 15. (Angus M. Thuermer Jr/WyoFile)

During the dog days of summer, Wyoming residents take to the water to beat the heat and perhaps wet a line.

While people can cool off on the water, trout and kokanee salmon already are there and become more vulnerable when temperatures rise. Wyoming Game and Fish Department this week warned catch-and-release anglers that warm water imperils some fish.

Green River Fisheries Supervisor Robb Keith pointed to Flaming Gorge and the Green River as two places anglers should exercise caution. “With current warm water temperatures anglers need stop to catching and releasing kokanee,” Keith said in a statement.

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Dredging kokanee up from depths, where water is colder, to the warm surface stresses them to the point that they often die. Trout in the Green River also can be harmed by catch-and-release fishing.

“Trout experience significant mortality at prolonged exposure to water temperatures greater than 75 degrees Fahrenheit and brief exposure to temperatures over 80 degrees are lethal,” Keith said. He urged anglers to stop casting when they the water gets as warm as 70 degrees.

In the photo above, Brian Upesleja casts toward the bank of the Hoback River as Luke Smith rows. Upesleja began his full day of fishing at 6:30 a.m. on the Green River and topped it off with this evening float on the Hoback and Snake rivers.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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