You got the idea right Beezer, but the wrong muscle. The dark meat is slow twitch muscle for cruising, maintaining balance, and is basically active all the time and well supplied with blood vessels, which makes it dark and usually makes it taste strong. The salmon colored meat that we eat is the fast twitch muscle and is used for bursts of speed, is not well supplied with blood, and builds up lactic acid quickly, which is the reason the fish wears out fast when he puts up a fight. I usually trim out the dark meat.