Thank you all for your opinions! I think, to come to a truthful position about something like this, you can't worry about stepping on toes. So don't worry about that in this thread. The world is full of unanswered questions and correspondingly bad policies simply because people are afraid to rock a boat (Bay of Pigs comes to mind...)
So far, we've only dredged up one more study (thanks PeteCz!). It would certainly be nice if more of us could cough up some more numbers, if you have them.
Kytroutman, it would be wonderful if we could find what data they base such a strong policy decision on. I'll look for that. If I find it, I'll report it back here. I will say that what happens in large western rivers with their sparse tree cover and large, sprawling acreage doesn't seem nearly as like our small-mountain-stream-Smokies as say, So Cal streams. It may be that small trout survive high temps a lot better than large ones, as some bass studies show. And well, the Smokies are full of 6-8" fish, as opposed to 15-18 " fish everywhere in the Yellowstone area. It could even be that that some of the factors causing the lethality in the Yellowstone area could be the same factors causing the fish to grow so large and abundant! Like say, the Firehole keeping the Madison at better growing temperatures for some of the winter, and the higher fertility loads (and thus higher pathogen loads) of western rivers.
As an example of something that people have long believed, and strongly, we could point to fishing for spawning bass. For many, many years it was common wisdom that you don't fish bass on nests, because that would impact their numbers. So streams were closed until after the spawn. Yet many studies have shown exactly zero impact on bass numbers when anglers are allowed to fish them off nests. The reality of that situation is that when you have a lake with a billion eggs, 99.9xxx percent of them die anyway. Killing a few million eggs just doesn't hurt anything. Slowly, policies have changed to reflect reality (I'm headed to NY in a few weeks and have read about locals being mad about biologists eliminating the spawning fishing bans on their local creeks and lakes. What that really means is that no amount of data can convince some people).
I feel that surely someone has the numbers that we are looking for. Policy decisions based on gut feelings are wrong more often than those that have good facts backing them up.
If we really are impacting the fish population during these high temps, then shouldn't our fisheries folks be closing our streams too? Or at least issuing some kind of official opinion? Also, does anyone know if the closures in Yellowstone are official, or if they are some kind of voluntary mouth-to-mouth thing controlled by the fly shops? I'm not passing judgment on it; I'm just curious.
Byron, if you are reading this thread, it would be interesting to hear your take on it. One can tell that you are very concerned about the fish, and it would help to know what things you've seen, heard, and read to come to the conclusions you have. Your opinion carries a heavy weight!