The blue maomao (''Scorpis violacea''), also known as the violet sweep, blue sweep or hardbelly, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

, 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 botanical subfamily names with "-oideae", and zo ...

Scorpidinae The Scorpidinae, commonly known as halfmoons, knifefishes, and sweeps, are a subfamily of the family Kyphosidae, the sea chubs, a family of marine fish in the order Perciformes. The Scorpidinae are distributed throughout the Pacific and east In ...

, part of the

sea chub The sea chubs, also known as rudderfish and pilot fish and in Hawaiian as ''enenue'' or ''nenue'', are a family, Kyphosidae, (from Greek, ''kyphos'' = hump) of fishes in the order Perciformes native to the Atlantic, Indian and Pacific Oceans u ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Kyphosidae. It is native to the southwestern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

from

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

and the

Kermadec Islands The Kermadec Islands ( ; ) are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga. The islands are part of New Zealand. They are in total area and uninhabit ...

, where it can be found in inshore waters from the surface to depths of . This fish can reach a length of . It is commercially important and is also a popular

game fish Game fish, sport fish or quarry refer to popular fish species pursued by recreational fishing, recreational fishers (typically angling, anglers), and can be freshwater fish, freshwater or saltwater fish. Game fish can be fish as food, eaten aft ...

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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. They can grow to a

fork length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured fr ...

of . The

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

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 ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

, New Zealand, the

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 Cleaner fish are fish that show a specialist feeding strategy by providing a service to other species, referred to as clients, by removing dead skin, ectoparasites, and infected tissue from the surface or gill chambers. This example of cleaning ...

when there is no apparent need for them to be cleaned. They

spawn Spawn or spawning may refer to: * Spawning, the eggs and sperm of aquatic animals Arts, entertainment and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** ''Spawn: Armageddon' ...

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. 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 Wellington is the capital city of New Zealand. It is located at the south-western tip of the North Island, between Cook Strait and the Remutaka Range. Wellington is the third-largest city in New Zealand (second largest in the North Island ...

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 of the Pacific Ocean Fish described in 1873 Taxa named by Frederick Hutton (scientist)