Ostorhinchus norfolcensis
Small reef cardinalfish logged around New South Wales and Norfolk Island in 21.4-26.6C water, usually spotted alone or in small uncommon groups.
A small, deep-bodied fish reaching around 10cm, with the big-eyed, blunt-faced look typical of cardinalfish. Look for a compact, slightly compressed body held in a stiff hover close to reef structure rather than swimming in the open. Its size and stillness are the giveaway underwater more than any single bold marking, so a careful look at body shape and posture near ledges and crevices helps confirm it against similar cardinalfish.
Divers typically find it holding a fixed position near ledges, overhangs or reef crevices rather than out in open water, consistent with the sheltering habits of cardinalfish generally. It is logged mostly as uncommon or rare, so sightings tend to be of one or a few individuals rather than large aggregations, with just one site recording it as common. Expect a fish that sits still and lets you approach slowly rather than one that bolts at the first sign of a diver.
Like other cardinalfish, this species is a mouthbrooder, meaning one parent carries the fertilised eggs in its mouth until they hatch, a trait shared across the whole Apogonidae family.
There is no clear seasonal pattern in the sighting data, so treat this as a year-round fish on the sites where it occurs. Observed water temperatures range from 21.4 to 26.6C, a spread wide enough to cover most of the year in its temperate to subtropical range.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most divers log this species around New South Wales in Australia, which accounts for the bulk of recorded sightings. It also turns up around Norfolk Island itself, giving the species its common name, though sightings there are less frequent than in mainland New South Wales waters.
Mapping where Norfolk Cardinalfish is logged…
The most reliable region is New South Wales, Australia, where most logged sightings come from. It has also been recorded around Norfolk Island, the location its common name references.
Sighting data shows no strong season, so it is considered a year-round species on the sites where it occurs. Observed water temperatures of 21.4 to 26.6C span much of the year in its range.
Look for a small, deep-bodied fish around 10cm with the large eyes and blunt face typical of cardinalfish, holding still near reef ledges and crevices. Body shape and its stationary posture near shelter are more useful clues than a single standout marking.
They reach around 10cm in length, a typical size for a small reef-dwelling cardinalfish.
No, they pose no threat to divers and are simply small, sheltering reef fish that tend to hold still as you approach.
Like other cardinalfish, it is a mouthbrooder, with a parent holding the eggs in its mouth until they hatch, a distinctive reproductive strategy shared across the cardinalfish family.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Iridescent Cardinalfish
1,784 sites
