Hamachi (young yellowtail): Yellowtail is the common name of a number of species of amberjack -- sleek migratory fish similar to the tunas. The japanese variety called hamachi has light golden flesh and may display a dark streak along the edge of a fillet, a characteristic of the two-toned musculature of fish that cruise the open seas. Since hamachi is not listed on many American sushi menus, it may be overlooked. It's one of the most rewarding discoveries you can make at a sushi bar.
Hamachi can be as rich as toro, smooth and buttery with a deep smoky taste, but not as overpoweringly fatty. The area around the pectoral fins is considered the tastiest part and is often set aside for special customers. Some sushi bars grill the skeleton and the bits of meat left on it and serve it as an appetizer or snack.
Although varieties of yellowtail are plentiful in waters off both U.S. coasts, hamachi are usually flown in frozen from Japan, where they are raised in hatcheries and harvested when they weigh between fifteen and twenty pounds -- just right for sushi. Yellowtail caught here are usually too lean to qualify.
Hamachi is available for import year round, but you may have to try a few sushi bars before you find it."