As their name suggests they have three dorsal fins. They also have a single tentacle half way between their nose and eyes.

Most common in depths less than 5m. Usually found in rock pools.

Prey on small crustaceans, worms and other small fish.

They lay eggs on smooth rocks or rubble and the males fiercely guard the eggs until hatching, approx 20 days. Males have been known to attack and chase away other creatures much larger than themselves.

Paulin, C. and C. Roberts 1992 The rockpool fishes of New Zealand (Te ika aaria o Aotearoa). Museum of New Zealand (Te Papa Tongarewa).