The fish would swim every which way and run into each other. So they decided that they needed a king. To choose the king they had a race.
All the fish lined up and started the race. The sole swam as fast as he could, but the herring took first place. The sole was jealous that “the naked herring” won. Thus, as punishment, his mouth has been on one side since then.
If you didn’t know, sole are flatfish that have both eyes on one side.
So the sole basically said “The King has no scales” and is then punished for that? Is the herring some sort of despot unable to take a joke? Wouldn’t being the slowest fish be punishment enough?