Cook’s Cardinalfish

The Ostorhinchus cookii, commonly known as Cook's cardinalfish, Cook's soldierfish, blackbanded cardinal, or blackbanded cardinalfish, is a marine species belonging to the Apogonidae family.

This tropical, marine, and reef-associated fish can attain a maximum length of 10 cm and is typically found in depths ranging from 1 to 10 meters. It inhabits the subtidal zone, often residing near ledges of rocky areas or coral reefs during daylight hours. Ostorhinchus cookii is primarily nocturnal and tends to be solitary or form small groups.

The species exhibits a whitish coloration with 5–6 stripes varying from dark brown to yellowish. A notable feature is the stripe originating at the upper rear corner of the eye, which is incomplete, along with a midlateral stripe that culminates in a distinct black spot at the base of the caudal fin. Additionally, a dark spot at the middle of the caudal fin base merges with the midlateral stripe.

During reproduction, Ostorhinchus cookii is known for its mouthbrooding behavior and forms distinct pairings throughout courtship and spawning.