One of my best fishing buds is a muskie freak, and despite knowing he can whack them all summer, he diligently puts up the muskie tackle by the end of June and usually won't touch it again until late September. I try to avoid targeting trout and river stripers once the temp jumps above 70. What people often don't understand, at least I think, is that it's not the hot water directly that will kill the fish. They can survive provided they're left alone in the little cold-water seep they've found, or in the cooler bottom of a pool. The death sentence is making them expend energy fighting, because it's much harder for a fish to catch its breath in hot water when the battle is done.