Bony fishes

CardinalsApogonidae

Family47 species

The male holds the eggs in his mouth, and for as long as he holds them he does not eat.

A cardinalfish clutch is not a loose scatter of eggs. They are bound to one another by fine threads into a single ball, and that is what makes the thing portable: the male takes it at spawning and carries it in his throat, rolling and reshuffling the mass so that clean water keeps moving through the middle of it. A brooding male is obvious once you know the shape. The jaw is distended, the head looks wrong, and he sits a little apart from the group with his mouth shut on a week or more of work.

The rest of the family's biology follows from that decision. A reef fish this size normally spawns into open water, releases eggs by the thousand and accepts that almost none of them come back; a cardinalfish makes a small clutch and guards nearly all of it through to hatching. The accounting is not sentimental. Males have been recorded swallowing part of a brood, and sometimes the whole of it, when the cost of the fast outweighs what the eggs are worth.

By day they are the easiest fish on the reef to find and the least rewarding to watch: a packed cloud of silver bodies under a ledge or inside a cave mouth, holding station in the shade, with an eye that takes up much of the head. The feeding is done in the dark, out over open reef, where divers are not.

Forty-seven species are listed here, and separating them is a real problem - a stripe through the eye, a spot at the base of the tail, a bar that comes and goes with mood. Several of them are known from this sea and nowhere else.

How to recognise cardinals

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

notably large eyes
prominent mouth
two distinct dorsal fins
dense aggregations in reef crevices or caves during day

47 species in Cardinals

Apogon

What the split left behind. The species still here are one kind of animal: small, plain red or pink, unmarked or nearly so, and pressed deep into caves, crevices and rubble by day. A cardinalfish that is red, patternless and inside the reef rather than hanging in front of it is usually one of these.

Campbell's Cardinalfish

Apogon campbelli

Oblique-Banded Cardinalfish

Apogon semiornatus

Redmouth Cardinalfish

Apogon erythrosoma

Ruby Cardinalfish

Apogon coccineus

Talbot’s Cardinalfish

Apogon talboti

Apogonichthyoides

Deep-bodied, brown and solitary, each with a dark bar through the eye and a blotch or a ringed ocellus on the side or at the tail base. They work low over rubble and silt rather than over coral, and they are not found in the packed shoals the family is known for.

Banded Cardinalfish

Apogonichthyoides taeniatus

Bullseye Cardinalfish

Apogonichthyoides pharaonis

Endemic

Sidespot Cardinalfish

Apogonichthyoides heptastygma

Timor Cardinalfish

Apogonichthyoides timorensis

Cheilodipterus

The only cardinalfishes with true canines. Every other genus in the family works with small teeth; these carry proper fangs in both jaws and take fish where their relatives take plankton. Bold dark stripes running the length of the body, and usually a spot at the tail base.

Arabic Cardinalfish

Cheilodipterus arabicus

Five-lined Cardinalfish

Cheilodipterus quinquelineatus

Endemic

Lachner’s Cardinalfish

Cheilodipterus lachneri

Large-Toothed Cardinalfish

Cheilodipterus macrodon

Twospot Cardinalfish

Cheilodipterus novemstriatus

Fowleria

Identified by a false eye on the gill cover. Most of the genus carries a dark ocellus there, which is the quickest way to place a small mottled cardinalfish that otherwise offers nothing to work with. Stout, cryptic animals of rubble and weed rather than of schools.

Crosseyed Cardinalfish

Peppered Cardinalfish

Fowleria variegata

Nectamia

Small groups living inside branching coral, and the tail base is where the identification sits: a ring or a saddle around it rather than the round spot the rest of the family uses. Another genus pulled back out of Apogon.

Brown Cardinalfish

Nectamia fusca

LCEndemic

Ringtail Cardinalfish

Ostorhinchus

The genus most of this page belongs to, and it barely existed until 2014: a molecular revision raised it from a subgenus and moved the bulk of the Indo-Pacific species out of Apogon into it. Dive guides, older books and most photo sites are still a generation behind, so expect to meet the same fish filed under Apogon everywhere else.

Endemic

Anklet Cardinalfish

Ostorhinchus pselion

Blackstriped Cardinalfish

Ostorhinchus nigrofasciatus

Cook’s Cardinalfish

Ostorhinchus cookii

Flower Cardinalfish

Ostorhinchus fleurieu

Goldbelly Cardinalfish

Ostorhinchus apogonoides

Offshore Cardinalfish

Ostorhinchus bryx

Yellow-striped Cardinalfish

Ostorhinchus cyanosoma

Pristiapogon

Named for a saw. The preopercle - the bone along the rear edge of the cheek - is serrated on both its margin and its ridge, and that is the character the genus is built on. It is also the one thing here you will never see underwater; in a photograph you work from the seven dorsal spines and the stripe through the eye instead.

Bridled Cardinalfish

Pristiapogon fraenatus

Iridescent Cardinalfish

Pristiapogon kallopterus

Narrowstripe Cardinalfish

Pristiapogon exostigma

Rhabdamia

The glass cardinalfishes. The body is translucent enough to show the spine and the gut through it, and they hang in dense schools, sometimes hundreds at a time, out over coral heads in open water - the opposite of the family habit of sitting still under a ledge.

Blackbelly Cardinalfish

Rhabdamia nigrimentum

Onespot Cardinalfish

Rhabdamia spilota

Taeniamia

Translucent fish ruled with fine lines along the body, in shoals that hold almost motionless through the day. Older books and photo archives file them under Archamia.