Female mottled brown with small saddles along back. Male reddish with black head during spawning season; rear half of body often dark with two white bands. Usually narrow white or light bar at tail base. First dorsal fin is noticeably shorter than second in females (50% of height) and slightly shorter in male (75% of height).

Restricted to offshore locations such as Lord Howe and Norfolk islands. Not present on mainland Australia. NB: map and database records to be updated when resources permit.

Similar E. atrogulare (Ringscale Threefin) has comparatively longer first dorsal fin (at least 75%, but often same height as second dorsal). Easily separated by location as it is not found offshore from mainland Australia.

Males of other Enneapterygius threefins can have black heads; e.g. E. larsonae (Blackhead Threefin) and E. similis (Masked Threefin).

• Max Size: 4 cm
• Sea Temperature Range: 18.7-25.2°C
• Depth: 0-6m
• Habitat: Coral Reef, Rocky Reef
• Habitat Generalisation Index: 12.2
  Also referred to as the SGI (Species generalisation index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here

• IUCN Threat Status: Not Evaluated
• Occurrence: Common (23% of sites)
  Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed
• Abundance: Many (26 per transect)
  Abundance is calculated as the average number of individuals recorded per RLS transect, where present.