A lot of talk about water temps lately so lets break it down. First we have to understand that oxygen density in water varies do to water temperature. The colder the water the more oxygen the water carries. Moving water, like in a river, will also carry more oxygen then not moving water as well. During the heat of summer, fish will often hide on the bottom of fast moving water. Conversely, in the winter, fish will often live in slow deep pools. Food sources will always factor into this as well, calorie intake vs energy expelled. The point here is that multiple factors will determine where fish live and where fish feed. In the Winter, the water is cold(high oxygen density), making it easy for fish to conserve energy. In the Summer, as the temps increase (lower oxygen density), fish will have to expel much more energy to survive, but nature provides ample food sources during the summer for fish to sustain them as they expel energy. To a point. Ideal trout temperatures: 45 - 65 degrees with the low 50's being ideal. Keep in mind, hatch timing is also dependent on water temps. Many factors determine these things, but they do go hand in hand.
Now lets take this knowledge and apply it to our current situation: Super low snow-pack, Hot dry summer forecast. If we continue to fish when the water temps go above 65 degrees the idea of catch & release go's out the window. Over 70 degrees and the survival rate plummets even faster. Lactic Acids build up as you fight your fish, severely limiting a fishes chances of survival.
What will happen? Will they shut down the rivers? Will we have a major fish kill off no matter what we do? I don't have the answers. But I do know that over 65 degrees and I'm done. Not worth it. Your going to hear a lot of guides/flyshops say 70 degrees. I call bullshit. Why push it? Money? Pride? whatever. If your a guide, and this go's for any guide anywhere: first and foremost your a steward of the river you work on and pushing the limits for a buck is wrong. In this case, dead fish wrong.