Opalfish

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Opalfish
Drawing by Dr Tony Ayling
Drawing by Dr Tony Ayling
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Percophidae
Subfamily: Hemerocoetinae
Genus: Hemerocoetes
Species: H. monopterygius
Binomial name
Hemerocoetes monopterygius
Schneider, 1801

The opalfish, Hemerocoetes monopterygius, is a duckbill of the genus Hemerocoetes, found only around New Zealand, at depths of between 5 and 200 m. Their length is between 10 and 25 cm.

The opalfish is a long slender fish of round cross-section, with a flattened snout giving rise to the family name of duckbill. The dorsal and anal fins are long and high, and the caudal fin has pointed lobes the upper having a long filament in large specimens. The mouth contains many minute bands of teeth in each jaw which are used to grasp the small crustaceans and fishes which are its diet.

Body colour is pale brown above with short dark bars on the back, and a silvery belly. There are iridescent blue and orange markings on the head and flanks, and blue bands on the dorsal and anal fins.

Opalfish are found all around New Zealand, but are most abundant off the east coast of Northland.

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