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

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

, 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 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 Ind ...

, 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, of fishes in the order Perciformes native to the Atlantic, Indian and Pacific Oceans usually close to shore in marine w ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Kyphosidae The sea chubs, also known as rudderfish and pilot fish and in Hawaiian as ''enenue'' or ''nenue'', are a family, Kyphosidae, of fishes in the order Perciformes native to the Atlantic, Indian and Pacific Oceans usually close to shore in marine w ...

. It is native to the southwestern

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

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 ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

and the

Kermadec Islands The Kermadec Islands ( mi, Rangitāhua) 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 are ...

, 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 Game fish, sport fish or quarry refer to popular fish pursued by recreational anglers, and can be freshwater or saltwater fish. Game fish can be eaten after being caught, or released after capture. Some game fish are also targeted commerciall ...

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 Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

. The

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

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

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: * Spawn (biology), 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: ...

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 Wellington ( mi, Te Whanganui-a-Tara or ) 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 second-largest city in New Zealand by me ...

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