Blue-eye Cardinalfish

Description

Although the maximum recorded standard length of O. compressus is 12 cm, its most common adult length is around 8.5 cm. Adults are pinkish-white, with six brown stripes along each side, iridescent blue eye rings, and up to four brown spots on the caudal peduncle (tail base). Juveniles begin with a black spot on a yellow caudal peduncle, which appears to mimic juveniles of certain piscivorous species of Cheilodipterus.

Distribution

Ostorhinchus compressus occurs in Australian waters from the Scott Reef, Ashmore and Cartier Islands, and Rowley Shoals in Western Australia; and from the Great Barrier Reef to the Middleton & Elizabeth Reefs Reserve and Lord Howe Island in the Tasman Sea. Its wider distribution extends through the Indo-Pacific from the Andaman Sea to Vanuatu and New Caledonia and as far north as southern Japan.

Habitat

Generally found from 2–20 metres, adults rest during the daytime in floating mixed species groups with other Apogonids. They are not very picky, being found resting in association with several kinds of live hard coral, Gorgonians, dead coral, rubble, and sand. Possibly because of the low water circulation, higher temperatures, and high oxygen consumption of some of the shallow branching corals into which O. compressus retreats from predators, it has been found to tolerate very low dissolved levels of oxygen, even at a temperature of 30 °C (which is likely to stimulate a relatively high resting metabolic rate).