Tuna II

Gavin described catching the second tuna on the way to California. They're interesting fish, as well as being delicious. My guess was that they were Bluefin, but once we got into Wikipedia range, it turned out that they were actually Bigeye tuna, better known to sushi-eaters as ahi. We ate a lot of it along the way. It doesn't take much preparation, just cut the raw fish into bite-size pieces, pour some soy over it, and add a few dabs of wasabi.

They're built quite a bit differently than salmon and trout with long, wing-like fins and bodies that taper sharply at the tail. I've heard that their shape is ideal for fast, long-distance swimming--the fish's equivalent of a marathoner's build. As with sails and airfoils, long, high-aspect fins are the most efficient. Salmon and trout are built more like sprinters. They have longer bodies, a little more muscular near the tail, and broad fins that get a lot of purchase on the water for bursts of speed. Another interesting thing about the tuna is that they don't have a spinal artery like most fish. Instead, they have a dark red section of very vascular muscle surrounding the spine. This kind of muscle is loaded with myoglobin, an oxygen-binding molecule that lets the muscles carry the oxygen they need for sustained exertion.

-Jared