Ringtail Cardinalfish

Ostorhinchus aureus

Ringtail Cardinalfish (Ostorhinchus aureus) is a small nocturnal reef-associated cardinalfish found in tropical Indo-Pacific waters and widely reported from coral and rocky habitats. It shelters by day and feeds at night on tiny crustaceans and plankton.

Saltwater

Ringtail Cardinalfish reference image — Rickard Zerpe, cc-by, via Wikimedia Commons. Source: Wikimedia Commons.

Identification points

Distinct dark ring or ring-like marking at the base of the tail
Small, slender cardinalfish body with a large eye
Pale body with yellowish to silvery tones and a forked tail

Habitat

Coral reefs, outer reef slopes, lagoons, and rocky areas, usually near cover such as ledges, branching corals, and crevices in shallow to moderate tropical marine water.

Bait notes

Not a standard angling target. If taken incidentally, tiny pieces of shrimp, mysid, or squid can work; very small soft plastics or micro-jigs are the closest lure options.

Behavior

A nocturnal planktivore and microcarnivore that stays close to shelter during the day, often in small groups; rises into the water column after dark to feed on zooplankton and small invertebrates.

Caution

Marine reef species; consumption is generally not a major issue, but local reef-fish advisories should be checked because site-specific contamination can occur. As with many small reef fish, use caution with handling to avoid spines or abrasion.

Fishing notes

Best approached with light micro-tackle around reef edges at night or dusk, but it is usually caught only incidentally on small bait rigs. Handle gently and release quickly if not needed.