GoatfishesMullidae

A goatfish at work collects a crowd, and none of it is helping.

Watch one on a sand patch beside the reef: head down, tail up, driving into the bottom, and behind it a wrasse, then a second wrasse, then an emperor and a lizardfish holding station a body length back. Nothing in that line digs. They are there because the goatfish flushes animals out of the sediment that it does not always catch, and a shrimp that bolts into open water is a free meal for whoever is closest. Biologists call the digger a nuclear species and the crowd its followers, and on a 🌊 Red Sea sand flat the goatfish is the most dependable nucleus there is. Some followers go further and simply take the item out of the barbels.

It can afford the tax because it is finding food that nothing else on the flat can find. The pair of barbels under the chin are chemical sensors, and what they do in sediment is on the species pages; the point for the family is that sand is not empty ground, it is a dense layer of worms, crustaceans and small molluscs with no way to be seen. A goatfish reads it by touch and taste and eats out of a larder that is closed to everything with only eyes. The cost is that it works with its face in the bottom, which is a poor way to watch for anything coming.

The family runs two shifts and two lifestyles. The Mulloidichthys goatfishes gather by day in yellow-striped clouds that hang motionless in the shade of a coral head doing nothing whatever, and disperse to feed after dark. The Parupeneus species mostly work alone and in daylight, one sand patch at a time. One of them, the goldsaddle, gave up sediment altogether and hunts fish instead, probing its barbels into holes to drive them out, sometimes in a pack.

They also change appearance faster than most people expect, switching between pale sand tones and heavy red blotching in seconds depending on whether they are feeding, resting or being chased, which is a good way to lose track of which species you photographed. Nine are listed here. And on a European menu these are the red mullets, which they are not: the real mullets are a separate family with a separate page in this catalogue and a completely different way of eating.