EmperorsLethrinidae

Most of what an emperor eats is already hidden when it starts looking.

The family works the sand, the rubble and the seagrass beside a reef rather than the coral itself, and it is equipped for digging rather than for chasing. A long sloping face with the mouth at the end of it, thick lips, and a habit of nosing into the bottom and blowing a pit clear to see what comes up. The teeth match the job: canines at the front to grip, and behind them rounded molars set along the side of the jaw that crush a snail shell, a crab or the test of an urchin. The wreckage is spat out and the meat swallowed.

Most of this happens at dusk and through the night. By day emperors hang in loose company off the reef edge, and the sand flat they spent the night working looks empty.

They are also the fish most people give up on identifying. A dozen near-identical silver-bronze shapes, and the marks that separate them, a red patch on the gill cover, blue lines radiating from the eye, a yellow lip, sit on an animal that can switch its blotches and bars on and off in seconds with its mood. The one dependable family character is a negative: an emperor's cheek carries no scales, which is what tells it from the snapper it is otherwise easy to confuse with. Most of them begin life as females, so the biggest fish on a flat is usually a male that used to be one.

Twelve species are listed here, and they matter more to fishermen than to divers. Emperors are a staple catch the length of this coast, and the large ones are the first fish a net takes off a sand flat.