The Six-spined Leatherjacket is often recognised by the intricate pattern of fine blue lines on the head, and yellow dorsal and anal fins. As with all Leatherjackets, their skin is covered by thick, minute scales giving the skin a feeling of sandpaper and roughness. The body colour of this species can vary greatly, where the males are usually blue with yellow blotches and irridescent scribbling around the edge of their bodies.The females are yellow or brown with a number of broad brown stripes across the body. A block of strong spines (usually 6 but can be 5-8) are situated in front of the tail on males and are used to display aggression and dominance by hitting and slashing the sides of other leatherjackets particularly during the mating season. These spines are greatly reduced in size on female specimens. Six-spined Leatherjackets exhibit the characteristic dorsal spine on top of the head, which can be raised or lowered as required, however is not known to be venomous.
The Six-spined Leatherjacket is endemic to southern Australia, occurring from Jurien Bay, WA to Broughton Island, NSW. Both mature animals and juveniles are common in seagrass beds and sponge gardens, but some individuals choose to migrate into deeper coastal rocky reefs as they mature. Six-spined Leatherjackets come together in large schools for mating between late winter and autumn where the males compete for dominance by displaying their dorsal spine and slashing their spiny tails at one another. The rest of the year is spent either in small aggregations or solitary on the reefs. They feed on urchins and shellfish and reach a maximum length of 55 centimetres.
Other common names include Variable leatherjacket, Reef leatherjacket
Occurrence at the Busselton Jetty
One of the larger Leatherjackets encountered at the Underwater Observatory on a regular basis, the male Six-spined Leatherjacket is often seen swimming across the seafloor. They can be quite variable in its colouring but generally shows an olive green base with an oval mottled pattern with irridescent blue scribbles on each side. Easily recognised by their distinctive shape and clump of six spines at the base of the tail.