GroupersEpinephelidae

A grouper's teeth are not for cutting. They are small, they curve backward, and their only job is to keep a fish that is already inside the mouth from getting out again. Nothing in the head reduces a meal to pieces. Everything a grouper eats goes down whole, which means the limit on its diet is not what it can catch but what will pass through its own throat, and that is why the family runs to enormous heads and very wide mouths. The strike is a gulp of water, over before it registers.

Then the fish goes back to its ledge and stays there. A grouper has no cruising gear and no business in open water: the body is built for one acceleration from a standing start, and the rest of the day is spent sitting somewhere with a view, which is also why one species here can afford to recruit moray eels to flush prey out of holes for it. Individual groupers hold the same few square meters of reef for years. Guides take visitors to a particular fish, and the same animal turns up in photographs a decade apart.

That combination is what makes them the first thing a reef loses. Groupers grow slowly, live for decades, begin life as females and turn male later, and several species gather at the same corner of the same reef on the same few days each year to spawn. A fishery that takes the big fish takes the males; one that finds the aggregation takes the entire breeding population in a week. A large grouper that sits in the open and lets you approach is telling you how that reef is managed.

Twenty-six species are listed here, from basslets the size of a thumb to the giant grouper at nearly three meters. Color is a poor guide to any of them: most shift between pale, barred and blotched within seconds, so the fish in your photograph may not match the plate in the book.