The blue maomao (''Scorpis violacea''), also known as the violet sweep, blue sweep or hardbelly, is a species of marine ray-finned fish, a member of the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

Scorpidinae, part of the sea chub family Kyphosidae. It is native to the southwestern Pacific Ocean from

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

to New Zealand and the Kermadec Islands, where it can be found in inshore waters from the surface to depths of . This fish can reach a length of . It is

commercially Commerce is the large-scale organized system of activities, functions, procedures and institutions directly and indirectly related to the exchange (buying and selling) of goods and services among two or more parties within local, regional, nation ...

important and is also a popular game fish.

Description

The blue maomao has a laterally, compressed and relatively deep body with a noticeably forked tail. 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. The juveniles are grey with a yellow

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. They can grow to a fork length. The dorsal fin has 9 spines and 27 soft rays and the

has 2 spines and 25 soft rays.

Distribution

Blue maomao are found in the southwestern Pacific Ocean around

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

, New Zealand, the Kermadec Islands and have been recorded in Australia.

Habitat and biology

The blue maomao is a schooling fish of inshore waters, especially rocky areas, which feed on zooplankton although when zooplankton are scarce they will graze on algae. When feeding in schools chasing shrimps near the surface they can cause the water to foam. Each fish has a favoured sleeping spot among the rocks during the night and they change colour from blue to mottle green at night. Occasionally they will sleep in groups over sheltered, sandy areas. They are tactile fish and when not feeding will rub themselves on pebbles and they will also visit cleaner fish when there is no apparent need for them to be cleaned. They spawn from September to November and the juveniles are recorded from October to December, the eggs are 0.8mm in diameter and contain an oil droplet. These fish can live to be 15 years old.

Species description

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

Fisheries

Blue maomao are a quarry for commercial fisheries in New Zealand where were landed in 2019. They are also popular with recreational fishermen, especially for spearfishing.

References

{{Taxonbar, from=Q1821099 Scorpis Fish described in 1873 Taxa named by Frederick Hutton