Latin name

Pentapodus emeryii

Other name

Purple threadfin bream or blue whiptail.

Identification

The scales on the head of the double whiptail extend to the posterior nostrils. The suborbital fin is scaleless. The lower limb is tarsal with 2 or 3 rows of scales. This species has excellent vision.

Features of fish fins

The dorsal fin of the double whiptail has 10 spines and 9 soft rays, while the anal fin has 3 spines and 7 soft rays. The pelvic fins are moderately long, almost reaching the anus. 

Fish colouring

A broad yellow stripe runs from the tip of the snout to the eye, where it splits into two thinner stripes, one running along the mid-flank to the caudal process, and the upper stripe running from the eye to the posterior end of the dorsal fin. The back is blue and the underside white. The caudal fin is iridescent blue and adult caudal fins have long wavy filaments extending from each blade.

Distribution

Widespread in the eastern Indian Ocean and western Pacific Ocean. It is found off the north-western coasts of Australia, Indonesia, Malaysia, Papua New Guinea and the Philippines. 

Habitat

Tropical marine species. Occurs at depths of 2 to 35 m (6 ft 7 in and 114 ft 10 in) on the clear slopes of coastal reefs.

Size

The maximum published total length of this species is 35 cm (14 inches), although the standard length is 18 cm (7.1 inches).

Behavior

A solitary species that may congregate in small groups. 

Food and feeding habits

It feeds on small fish, crustaceans, brittle stars and sipuncula.

Reproduction

There is an obvious sexual dimorphism in size: males are larger, females smaller. They may be protogynous hermaphrodites or males may grow faster than females. They spawn throughout the year with one or two periods of maximum breeding activity.

Fishing

Subsistence fisheries.

Relationship with a person

Harmless.