Bluestripe Butterflyfish

The bluestripe butterflyfish, like other butterflyfish, are laterally flattened fish up to 15 cm (6 in) long with pointed snouts and rectangular bodies. The dorsal fin has 12 to 14 spines and 20 to 21 soft rays, while the anal fin has 3 spines and 16 to 18 soft rays. The bluestripe butterflyfish has eight distinctive diagonal blue stripes radiating from the eye region, on a yellow background. There is a black spot at the top of the head and another larger spot of black at the base of the tail. This latter dark patch may serve to distract predators by encouraging them to attack the tail rather than the head end.

The bluestripe butterflyfish is endemic to the Hawaiian Islands where it is described as being abundant on coral and rocky reefs down to depths of about 28 m (90 ft).

The bluestripe butterflyfish is an omnivore, unlike some butterflyfishes which feed almost exclusively on corals. These specialists usually have mating systems involving a pair bond, but the omnivorous bluestripe butterflyfish lives in a more resource-rich environment, where it is easier to find sufficient food. As a result, males of this species operate a harem system, defending a territory which includes up to four smaller female territories.

The bluestripe butterflyfish was first formally described in 1828 by the English naturalist Edward Turner Bennett (1797–1836). The specific name honours Lieutenant John Frembly R.N., a marine surveyor and geologist, who presented a collection of fish specimens from the Sandwich Islands to the Zoological Society of London.