For a very brief time in my early twenties, I worked in a sushi bar in Albuquerque, New Mexico. Don't worry, this isn't a story of air-mailed, flash-frozen fish gone awry, nor is it a tale of a desert seafood-eater's existential crisis. I just want to make sure you know that you might be missing out on one of the best parts of the fish: the collar.
In this sushi bar, the hamachi kama (or yellowtail collar in English) was reserved for friends of the owner, kind regulars and very, very lucky, well-behaved employees. It also quickly became my favorite thing in the restaurant immediately after I tasted it. Don't let the name scare you. The hamachi collar (like on all fish) refers simply to the section just behind the head and gills. If you are not squeamish about seeing fish being butchered, you should absolutely check out this fantastic video of a tuna fisherman breaking down the collars on a yellowtail. As he says, "best part of the fish, right there."
Why is the collar so good? I can't tell you scientifically. I suspect that it has to do with the use of the muscles in that part of the fish, as well as the fact that it is one of the only pieces of fish that ever gets cooked on the bone, which is well-known to make everything taste better. The meat is sweet, tender, full of rich flavor and especially juicy. Hamachi kama is also good for you, since you can cook it with no added fat whatsoever -- it tastes best simply grilled, with at most a sprinkling of salt, soy and citrus. Eating the collar of the fish is also pretty green of you, considering that it uses a part of the fish that a lot of unaware eaters would consider scrap.
Hamachi kama is hard to find in restaurants, partially because it is scarce (there are only two collars on a fish) and partially because cooks are smart and they save the best parts for themselves. If you are in a Japanese restaurant and you see it on the menu, you would be laughing in the face of enjoyment and good flavor to not order it. They still might not have any left, but you always have to ask. Like the satisfaction that comes from picking the turkey carcass on Thanksgiving, eating a hamachi collar is an exercise in patience, rewarding those dextrous enough to dig in with chopsticks or brash enough to use their fingers. Don't miss it. I promise you won't regret it.