The whitefin trevally (''Carangoides equula''), also known as the horse trevally, is a species of deep water

offshore Offshore may refer to: Science and technology * Offshore (hydrocarbons) * Offshore construction, construction out at sea * Offshore drilling, discovery and development of oil and gas resources which lie underwater through drilling a well * Off ...

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

in the jack

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 ...

Carangidae. The species inhabits the

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

to temperate waters of the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

and central Pacific, ranging from

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

in the west to

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

in the east. The whitefin trevally is a moderate-sized fish, growing to 37 cm, and is distinguished by a number of morphological traits, including fin size,

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the ...

count, and colour. It inhabits the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and

slope In mathematics, the slope or gradient of a line is a number that describes both the ''direction'' and the ''steepness'' of the line. Slope is often denoted by the letter ''m''; there is no clear answer to the question why the letter ''m'' is use ...

at depths to 200 m over sand and mud substrates, where it preys on fish,

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 ...

s, and

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

s. Studies in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

indicate a length at sexual maturity of 17.4 cm on average, with spawning occurring between May and October, with each individual spawning multiple times. Whitefin trevallies are of high importance to

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

in Japan, where they are taken by trawlers, although the catch numbers have halved since the 1980s. It is of minor importance elsewhere throughout its range, but is considered a good

table fish Many species of fish are caught by humans and consumed as food in virtually all regions around the world. Fish has been an important dietary source of protein and other nutrients throughout human history. The English language does not have ...

Taxonomy and naming

The whitefin trevally is classified within the genus ''

Carangoides ''Carangoides'' is a genus of tropical to subtropical marine fishes in the jack family, Carangidae. They are small- to large-sized, deep-bodied fish characterised by a certain gill raker and jaw morphology, often appearing very similar to jacks ...

'', a group of fish commonly known as jacks and trevallies. ''Carangoides'' falls into the jack and horse mackerel family Carangidae, the Carangidae are part of the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Carangiformes Carangiformes is an order of the ray-finned fishes. The order is part of a clade which is a sister clade to the Ovalentaria, the other orders in the clade being Synbranchiformes, Anabantiformes, Istiophoriformes and Pleuronectiformes. The Carang ...

. The species was first scientifically described by Dutch naturalists

Coenraad Jacob Temminck Coenraad Jacob Temminck (; 31 March 1778 – 30 January 1858) was a Dutch people, Dutch Aristocracy (class), aristocrat, Zoology, zoologist and museum director. Biography Coenraad Jacob Temminck was born on 31 March 1778 in Amsterdam in the Dut ...

and Hermann Schlegel in 1844 based on a specimen taken from the waters off Japan, which was designated to be the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

. They named the species ''Caranx equula'', although the species was later moved to ''Carangoides'', as well as having a new genus created for it, ''Kaiwarinus''. This genus is currently considered invalid, though a 1988 review of the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

of the Carangidae found it to be valid, and to be the sister genus to ''

Pseudocaranx ''Pseudocaranx'' is a genus of ray-finned fishes from the family Carangidae, the jacks, trevallies, scads, and pompanos. They occur in the western Atlantic Ocean and the Indo-Pacific. Species Four recognized species are placed in this genus: * ' ...

'', not closely related to ''Carangoides''. The species was independently renamed as ''Carangoides acutus'' in 1974, but this is rejected as a junior synonym under

ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...

nomenclature rules. Specimens taken from Hawaii and

Easter Island Easter Island ( rap, Rapa Nui; es, Isla de Pascua) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is most famous for its nearl ...

in the Pacific Ocean initially had the name ''Caranx (Carangoides) dasson'' applied to them by the American

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Rive ...

and Snyder. This name was eventually synonymised with ''Carangoides equula'', but uncertainty still remains whether this population actually represents a separate species or

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

. The ''Carangoides dasson'' population has the same diagnostic features as ''Carangoides equula'', but exhibit more slender bodies and larger eyes, with William Vaniz-Smith indicating more research is required to determine the relationship between these populations. The name ''Caranx (Carangoides) dasson'' is still currently considered to be invalid by taxonomic authorities.

Description

The whitefin trevally is a relatively small fish, reaching a maximum known length of 37.5 cm. The species has a body shape similar to a number of other jacks, having a compressed, almost rhomboidal body, with the dorsal and ventral profiles approximately equally convex. The dorsal profiles of the snout and nape in the species are almost straight. Two separate

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 ...

s are seen, with the first having seven spines, while the second consists of one spine and 23 to 25

soft rays Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology co ...

. The first dorsal fin is moderately high, with the longest spine about as high as the soft dorsal-fin lobe is long, and is quite distinctive of the species. The

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 ...

consists of two

anteriorly Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

detached spines followed by one spine and 21 to 24 soft rays, with the pelvic fin having one spine and 18 or 19 soft rays. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

has a moderately strong anterior arch with the junction of the curved and straight sections occurring vertically below the twelfth to fifteenth soft rays of the second dorsal fin. The curved segment of the lateral line is longer than the straight section, which contains no to six

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

followed by 22 to 32 scutes. The breast is entirely scaled, or has a very small naked area anteroventrally. Both

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

s contain narrow bands of small teeth, with the outer teeth slightly larger. It has 27 to 32

s in total and 24

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

. The whitefin trevally is silver, with a blue to green dorsal surface, becoming silvery white below. The soft dorsal and anal fins are dusky yellow basally, with the anterior rays of both having dark grey-brown median and white distal bands. 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 se ...

is dusky yellow, while the pectoral and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are white. Juveniles have between 5 and 7 dark bands vertically on their sides.

Distribution and habitat

The whitefin trevally is distributed throughout the

and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

waters of the

region, although in a very patchily recorded distribution. In the western

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

, the species has only been recorded from

Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constituti ...

, and in the

Gulf of Oman The Gulf of Oman or Sea of Oman ( ar, خليج عمان ''khalīj ʿumān''; fa, دریای عمان ''daryâ-ye omân''), also known as Gulf of Makran or Sea of Makran ( ar, خلیج مکران ''khalīj makrān''; fa, دریای مکرا� ...

. In the eastern Indian Ocean, the species is known from northwestern

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 ...

, and definitely extends its distribution into the Pacific as far as

Okinawa is a prefecture of Japan. Okinawa Prefecture is the southernmost and westernmost prefecture of Japan, has a population of 1,457,162 (as of 2 February 2020) and a geographic area of 2,281 km2 (880 sq mi). Naha is the capital and largest city ...

. If ''Carangoides dasson'' is synonymous with ''Carangoides equula'', this extends the species distribution well into the Pacific, ranging to Hawaii and Easter Island. Before the species was recorded in Australia in 1988, the whitefin trevally was thought to only have an antitropical distribution. The fish probably has a more continuous distribution than currently known, with lack of adequate sampling contributing its patchily known distribution. The whitefin trevally is thought to primarily inhabit deep waters on the

and

between 90 and 200 m deep over

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

y and

mud A MUD (; originally multi-user dungeon, with later variants multi-user dimension and multi-user domain) is a Multiplayer video game, multiplayer Time-keeping systems in games#Real-time, real-time virtual world, usually Text-based game, text-bas ...

dy substrates. At least one record exists of the species in shallow

inshore A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past a ...

waters, where an individual was captured off a sandy

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shel ...

on Japan, but was thought to be stray fish. Two specimens were caught at the entrance of Durban Harbour, South Africa in December 2022, indicating that shoals travel into inshore waters of up to 20 metres.

Biology

The whitefin trevally is a benthic

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

, taking a variety of small fish,

s, and

s, either by foraging or chasing down its prey using its eyes which are extremely well adapted to the deep, low-light waters. Along with the

white trevally The white trevally (''Pseudocaranx dentex''), also known as striped jack,) is a jack of the family Carangidae widespread in tropical and warm temperate areas between 40°N and 47°S, in the Atlantic, Mediterranean, Indian, and Pacific Oceans. It h ...

, ''Pseudocaranx dentex'', it is the only member of the Carangidae to have the anatomy of its eyes examined, with the study finding excellent dark-environment sight due to the presence of a tapetum. The maturation and

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...

of the whitefin trevally have been extensively studied off

due to the species' economic importance in this region. Sexual maturity is reached at a minimum length of 15.1 cm, although most individuals reach maturity at around 17.4 cm length and every individual is mature by 24 cm. Although these parameters were calculated for female fish, observational data suggest the male life history is similar. In Japan, the species has a prolonged spawning season, from May to October, during which females spawn repeatedly, releasing between 13,862 and 79,899 eggs per batch. The growth of males and females is very similar, and both have similar lifespans. A length of 7.5 cm is reached after the first year, and lengths of 12.3 cm, 16.0 cm and 18.8 cm after the second, third and fourth years, respectively.

Relationship to humans

The whitefin trevally is a commercially important species in the waters off Japan, where it is known as , and of minor importance elsewhere throughout its range. For unknown reasons, the Japanese catch has decreased by half since the mid-1980s. It is taken primarily by bottom

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...

s on the continental shelf and considered to be a good

References

External links

EOL fact page
{{Taxonbar, from=Q2094371 whitefin trevally Fish of the Indian Ocean Fish of Hawaii Fish of South Africa Marine fauna of East Asia Marine fish of Southern Africa whitefin trevally