Of course there's genetic diversity. shade and color of skin, length, girth...just like people. Myself, I tried to differentiate dialect. However when I catch trout and their mouth moves up and down, I can't hear them. We may never know, but other trout may hear them when they silently scream like that when we take them out of water and ther jaws move up and down as they are screaming in trout language. I tried to decipher once and I think he screamed "Stay away from the gray sowbug with the gold beadhead!!"
We'll never know for sure.....Don