The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
I had someone tell me that salmon develop lock jaw once in the stream and can't bite, which know not to be true, this was told to me by a gentleman that was head of the fishing dept at gander mtn.
I have heard from two salmon fishers that salmon make 5 runs up a river to spawn and on the fifth time they die.