Bluefinned butterfish

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Bluefinned butterfish
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Odacidae
Genus: Odax
Species: O. cyanoallix
Binomial name
Odax cyanoallix
Ayling & Paxton, 1983

The bluefinned butterfish, Odax cyanoallix, a cale of the genus Odax, is found only around Three Kings Islands which is about 80 kilometres north of New Zealand, in shallow reef areas where there is abundant brown seaweed. Its length is between 20 and 35 cm.

The bluefinned butterfish is a slender fish with a pointed snout. It is generally similar to its close relative the greenbone, but is slightly deeper-bodied, has larger scales, a different colour pattern, and is generally smaller. It changes its colouration as it grows, young fish being orange-brown with three rows of white patches down each side from the snout to the caudal peduncle, and dark brown reticulated markings on the back. Adult males have an olive-green body with a series of bright blue markings on the head and have greatly elongated dorsal and anal fins with blue borders. Their teeth are fused in each jaw to form a parrot-like beak, and they are herbivorous, living on seaweed, preferring Ecklonia radiata.

This species swim by rapid beats of their pectoral fins, whereas the greenbone uses body undulations.

Bluefinned butterfish are protogynous hermaphrodites, beginning life as females, later changing to males. Males establish large territories of up to several hundred square metres and spawning takes place during late winter. Larval bluefinned butterfish settle out of the plankton into dense patches of bladder kelp in shallow wave-swept water, where they are initially protected from predators.

Bluefinned butterfish were only discovered in 1978 and described in 1983.

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