It is native to the southwestern Pacific Ocean from Australia to New Zealand and the Kermadec Islands, where it can be found in inshore waters from the surface to depths of 30 m (98 ft).

They have protrusible jaws, equipped with a number of rows of small, closely set teeth, which are used to capture larger zooplankton.

The adults are deep blue dorsally and pale ventrally, at night they change colour to a mottled dark green.

They spawn from September to November and the juveniles are recorded from October to December, the eggs are 0.8 mm in diameter and contain an oil droplet.

[2] The blue maomao was first formally described in 1873 as Ditrema violacea by Frederick Hutton with the type locality given as Wellington.