what i noticed about smolts is they have darker black spots on their backs then the trout and they have bigger eyes and their tails are a bit different also. coho smols have big black spots on the op of their backs and so do chinook but like adult chinook the smolts have the splotchy big spots heres a coho smolt and il try to get a pic of trout and chinook smolts. could not a find a chinook smol pic tha was good enough,,he one i did find you were ot allowed to copy.. do on the right is a coho salmon smolt left is a baby rainbow. notice how big the coho's eye is? and the shape of the tail and ovals on the side is different too. this also confused me a while back so i looked up pictues and found the differences