Summer days are a beacon calling anglers to the water to cast out a fly and see what bites. But, those fishing in the hottest months should be aware of the effects warmer water has on fish, especially Wyoming’s trout. 

“Low water flows combined with high air temperatures cause water temperatures to get high enough to be lethal to trout,” said Alan Osterland, Wyoming Game and Fish Department fish division chief. “Warm water also holds less oxygen which can stress not only trout, but also all fish.” 

Trout experience increased mortality at prolonged exposure to water temperatures greater than 75 degrees Fahrenheit; brief exposure to temperatures over 80 degrees are lethal. Fish stress quicker in low-oxygen warm water, which greatly hampers a fish's ability to recover from the rigors of being caught. However, as water temperature approaches 70 degrees the chance for any fish species to survive being caught and released is reduced.  

Anglers who adjust their practices during the summer can help more fish survive the heat.

“As water temperatures increase anglers should monitor water temps while fishing. When water temperature hits 70 degrees, it is recommended anglers should stop catching and releasing fish,” Osterland said. “Anglers should practice self-restraint to help fish survive.”

The Game and Fish asks all anglers practicing catch and release to consider the following:

• Fish early in the morning while the water temperature is cooler.
• Carry a pocket thermometer to monitor the water temperature.
• If the water temperature is at or above 65 degrees, consider keeping what you catch within the regulations. If the temperature is 70 degrees or higher, do not attempt to catch and release fish.
• As water temperature increases, using the proper techniques to catch and release a fish become increasingly more important to help insure the fish has a chance to survive:
• Play and land fish as rapidly as possible to reduce exhaustion stress.  
• Keep the fish in the water as much as possible.
• Do not squeeze the fish or place fingers in the gills.
• Remove the hook gently. If hooked deeply, cut the leader.
• Flies and lures are recommended whenever many fish are being caught and released.
• Barbless hooks allow easier hook removal.
• If a fish is exhausted and cannot hold itself upright, and if regulations allow, consider having it for supper because the fish has a poor chance of surviving.

Osterland says these are not new regulations, just recommendations to assist with the conservation of the fishery resource. If water temperatures are too high, consider escaping the heat with a trip to another top-notch high country fishery where it’s cooler.