Bony fishes

PomacentridaePomacentridae

Family34 species

Some damselfish are farmers, and they mean it. A gregory or a jewel damsel holds a patch of dead coral rock about a meter across, and it does not simply feed there, it weeds: the algae it does not want are bitten off and carried out of the plot, and the ones it does want are left to grow into a dense turf. In some gardens the crop is a red alga that is now found almost nowhere except inside them, kept going by the fish that eats it. Where the plot needs to be bigger, the farmer kills coral to make room, biting the polyps off in a line along the edge until the bare skeleton is ready for turf to move in.

Then it defends the whole thing against everything: other damselfish, wrasses, a mob of surgeonfish passing through, and you. Being charged in the mask by a brown fish the length of your finger is a standard 🌊 Red Sea experience, and the fish is not confused about what it is doing. It is defending a food supply that took it months to build, against an animal a thousand times its size, and it usually wins, because you move on.

The other half of the family points the opposite way. Chromis hang in clouds above the coral heads, facing into the current and picking plankton out of it one item at a time, then drop into the branches at dusk; between them they work as a conveyor, moving open-water food onto the reef and leaving it there. Farmer and plankton-picker share one small oddity: a damselfish has a single nostril on each side of the snout, where nearly every other bony fish has two.

Thirty-five species are listed here, which makes them the most numerous fish on a 🌊 Red Sea reef and the ones divers look at least. The anemonefishes belong to this family too, and are covered separately.

How to recognise pomacentridae

OvalEgg-shaped body, deeper than it is thick - damselfishes, surgeonfishes.

small, oval body, typically 5-15 cm long
active, territorial on specific reef patches
single dorsal fin running most of the back
forked or notched tail fin
bold single-colour bodies or sharply contrasting bands

34 species in Pomacentridae

Abudefduf

The sergeants: the big, bar-sided damselfish of the shallows and the reef crest, feeding in midwater in loose schools rather than holding a plot. Males turn dark while guarding eggs on bare rock. The bars are the family name in every language; the marks that separate the species are on the tail and at the base of the pectoral fin.

Blackspot Sergeant

Abudefduf sordidus

PoisonousLC

Indo-Pacific Sergeant

Abudefduf vaigiensis

Scissortail Sergeant

Abudefduf sexfasciatus

Amblyglyphidodon

Deep, almost disc-shaped and pearly, built more like a small batfish than a damsel. They hang above the reef in loose groups instead of down in the rock, and the species are separated by which part of the body carries the yellow or gray wash.

Pale Damselfish

Amblyglyphidodon indicus

LCEndemic

Yellow-side Damselfish

Amblyglyphidodon flavilatus

Chromis

The plankton half of the family. They hang in clouds above a coral head facing into the current, pick items out of it one at a time, and drop into the branches together at dusk or at a threat - which moves open-water food onto the reef every day. Separating the species is done on the tail and the armpit: a dark bar, a black tip, a colored patch at the base of the pectoral fin.

Dascyllus

The coral-head damsels. Each group belongs to one branching colony and never leaves it - the whole lot drops into the branches at once when something comes, which is the behavior rather than the pattern that names them. Two of the species here are visually identical and are separated by range and genetics rather than by anything you can see.

LCEndemic

Blackbordered Dascyllus

Dascyllus trimaculatus

Neopomacentrus

Plankton-pickers of the mid-water, told by the tail: gray-brown fish with a clean yellow tail and yellow rear fins, hovering a meter above the bottom in loose groups rather than sitting on it.

LCEndemic

Miry’s Damselfish

Neopomacentrus miryae

Regal Damselfish

Neopomacentrus cyanomos

Yellowtail Damselfish

Neopomacentrus flavicauda

Pomacentrus

The largest damselfish genus here and the hardest to work with: six species of much the same size and build, separated on small differences in fin color and on a spot at the base of the pectoral fin. Most hold a small territory over rubble and dart back into it, somewhere between the farmers and the plankton-pickers.

Dark Damselfish

Pomacentrus aquilus

Reticulated Damselfish

Pomacentrus trichourus

Slender Damselfish

Pomacentrus leptus

Sulphur Damselfish

Pomacentrus sulfureus

Threeline Damselfish

Pomacentrus trilineatus

Whitetail Damselfish

Pomacentrus albicaudatus

Pycnochromis

Split out of Chromis recently, and the two species here make the split easy to remember: both are cut in half by a clean vertical line, dark in front and white behind, which no true Chromis does. Older books and photo sites still file them as Chromis.

Chocolatedip Chromis

Pycnochromis dimidiatus

Half-and-half Chromis

Pycnochromis iomelas

Stegastes

The farmers, and the ones that charge a diver. Each fish holds about a square meter of dead coral rock, weeds it - biting out the algae it does not want and carrying them off the plot - and defends the result against everything, including animals a thousand times its size. A patch of long turf standing out from the reef around it usually has one of these over it.