Sixband hawkfish

Lore & Background

The sixband hawkfish was first formally described as Cirrhitoidea sexfasciata in 1960 by American ichthyologist Leonard Peter Schultz, with the type locality given as Airy Island in the Bikini Atoll. In 1963, John Ernest Randall reviewed the family Cirrhitidae and created the new monotypic genus Isocirrhitus for this species, determining that Oliver Peebles Jenkins' Cirrhitoidea was a synonym of the genus Amblycirrhitus. The genus name may derive from iso meaning 'equal' and Cirrhitus, the type genus of the Cirrhitidae; the specific name sexfasciatus means 'six banded'.

The sixband hawkfish is quite similar to species in the genera Cirrhitops, Amblycirrhitus, and Cirrhitichthys, but those genera have teeth on the palatine and longer dorsal fin spines. It also resembles species in Paracirrhitus, but those have a single cirrus at the tip of each dorsal fin spine. This species has a tuft of cirri at the tip of each spine in the dorsal fin, with moderately notched membranes between the spines. The uppermost and five lower pectoral fin rays are unbranched, the upper third of the preoperculum edge has fine serrations, and the caudal fin is truncate. The overall colour is tan broken by seven wide, vertical blackish bands on the upper body, the first on the nape and the last on the caudal peduncle.

The sixband hawkfish occurs in the western Pacific Ocean, including the Cook Islands, French Polynesia at Rapa Iti, the Gilbert Islands, the Kiribati Line Islands, Marshall Islands, Tonga, and the United States Minor Outlying Islands at Howland Island and Baker Island. It is found in shallow water at depths between 1 and 11 m, associated with reefs.

Reader's Guide

The sixband hawkfish is significant as the sole member of its genus Isocirrhitus, a status established by John Ernest Randall in his 1963 review of the family Cirrhitidae. Its original description by Leonard Peter Schultz in 1960 as Cirrhitoidea sexfasciata, with the type locality at Airy Island in the Bikini Atoll, marks a specific point in the taxonomic history of hawkfishes. The species is one of the less colourful hawkfishes, with a tan body and seven wide vertical blackish bands, and reaches a maximum standard length of 7.8 cm. Its distribution across the western Pacific, from the Cook Islands to the Marshall Islands and Tonga, and its occurrence in shallow reef habitats between 1 and 11 m depth, define its ecological niche. The species' morphological similarities to other hawkfish genera, such as Cirrhitops, Amblycirrhitus, and Cirrhitichthys, are noted, but it is distinguished by the absence of palatine teeth and shorter dorsal fin spines, as well as by having a tuft of cirri on each dorsal fin spine rather than a single cirrus. The sixband hawkfish remains the only known species in its genus, underscoring its unique taxonomic position within the Cirrhitidae.

Did You Know?

• The sixband hawkfish is the only known member of the genus Isocirrhitus.
• It was first described in 1960 by American ichthyologist Leonard Peter Schultz.