The halfmoon (''Medialuna californiensis''), also known as the blue perch, is a species 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 h ...

, a

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 ...

from the subfamily

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

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

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 coasts of the eastern Pacific Ocean off western North America. It is fished for using hook and line and it is a desirable food fish.

Description

The halfmoon has an elongate, compressed, oval body with a small pointed head. It has a small, horizontal mouth in which the upper jaw is partially hidden by the orbital bone when the mouth has closed. Each jaw has a single row of pointed teeth. It has a continuous

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 c ...

which has 9-11 spines in the anterior portion which fold down into a scaly furrow, the posterior portion has 22-27 soft rays and these are higher than the spines. The anal fin has 3 spines and 17-21 soft rays. The

caudal 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 ...

is marginally concave. Most of the head and body is covered in small, thick and rough scales except foe the area forward of the eyes. The colour is dark bluish grey to grey dorsally, paler ventrally sometimes with faint, narrow, vertical bars along the flanks. It has a dark blotch on the upper corner of the gill cover. The margins of the dorsal, anal and caudal fins are dark and the outer edge of each lobe of the caudal fin is white. Juvenile fish are blue above and silvery below. The maximum recorded

total 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 ...

of the halfmoon is . The shape of the caudal fin is said to resemble a crescent moon, leading to the common name.

Distribution

The Halfmoon is native to the eastern Pacific Ocean along the western coast of North America from

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest by ...

in the north to the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

, although it is rare north of

Point Conception Point Conception (Chumash: ''Humqaq'') is a headland along the Gaviota Coast in southwestern Santa Barbara County, California. It is the point where the Santa Barbara Channel meets the Pacific Ocean, and as the corner between the mostly north ...

in California.

Habitat and biology

The halfmoon is frequently observed high in the water column over rocks and at middle depths over

kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwa ...

. Their preferred habitats are rocky reefs, kelp forests, floating kelp pads, and oil rigs. They are occasionally recorded near the surface of the water, but they are commonly found at depths between . This is an omnivorous species with kelp, red algae and green algae making up the bulk of its diet but it also feeds on a diversity of small invertebrates such as

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

s and sea anemones. They are schooling fish. The juveniles are occasionally reported far offshore, although they are more frequent around shallow subtidal areas and kelp beds with the adults. In their first year they can still be as small as and can be found in schools of a dozen or more on the outer edge of kelp beds and in sea grass beds. These fish reach sexual maturity when they attain a length of about which is when they are roughly wo years old. The

spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquat ...

season runs from June through to October and they are broadcast spawners. The fertilised eggs and newly hatched larvae are planktonic. The larvae are most numerous off northern

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

The juveniles will school with juvenile opaleye beneath floating rafts of kelp.

Fisheries

The halfmoon is a prized species for recreational anglers using rod and line, it is a bycatch in traps and bait nets. In California its season runs from August to April. The flesh is lightly flavoured and the fish can be eaten as fillets or whole and cooked in a variety of methods.

Species description

The halfmoon was first formally described as ''Scorpis californiensis'' in 1876 by the

Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationality law * Austrian German dialect * Something associated with the country Austria, for example: ...

ichthyologist Franz Steindachner with the type locality given as

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...

, California.

References

External links

* {{Taxonbar, from=Q3752666 Scorpidinae Western North American coastal fauna Fish described in 1876