The bluefin trevally (''Caranx melampygus''), also known as the bluefin jack, bluefin kingfish, bluefinned crevalle, blue ulua, omilu, and spotted trevally), 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 large, widely distributed
marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military
* ...
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 ...
classified 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 Carangidae are a family of ray-finned fish which includes the jacks, pompanos, jack mackerels, runners, and scads. It is the largest of the six families included within the order Carangiformes. Some authorities classify it as the only family ...
. The bluefin trevally is distributed throughout 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 ...
waters of the
Indian
Indian or Indians may refer to:
Peoples South Asia
* Indian people, people of Indian nationality, or people who have an Indian ancestor
** Non-resident Indian, a citizen of India who has temporarily emigrated to another country
* South Asia ...
and
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 ...
s, ranging from
Eastern Africa
East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa:
Due to the historical ...
in the west to
Central America
Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
in the east, including
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 ...
in the north and
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 ...
in the south. The species grows to a maximum known length of and a weight of , however is rare above . Bluefin trevally are easily recognised by their
electric blue fins, tapered snout and numerous blue and black spots on their sides. Juveniles lack these obvious colours, and must be identified by more detailed anatomical features such as
fin
A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...
ray and
scute
A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
counts. The bluefin trevally inhabits both
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 ...
environments such as bays,
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...
s and shallow
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...
s, as well as deeper offshore reefs,
atoll
An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gr ...
s and bomboras. Juveniles prefer shallower, protected waters, even entering
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
for short periods in some locations.
The bluefin trevally is a strong
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 ...
y fish, with a diet dominated by fish and supplemented by
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 and
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 as an adult. Juveniles consume a higher amount of small crustaceans, but transfer to a more fish based diet as they grow. The species displays a wide array of hunting techniques ranging from aggressive midwater attacks, reef
ambush
An ambush is a long-established military tactics, military tactic in which a combatant uses an advantage of concealment or the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbru ...
es and
foraging
Foraging is searching for wild food resources. It affects an animal's Fitness (biology), fitness because it plays an important role in an animal's ability to survive and reproduce. Optimal foraging theory, Foraging theory is a branch of behaviora ...
interactions with other larger species, snapping up any prey items missed by the larger animal. The bluefin trevally reproduces at different periods throughout its range, and reaches
sexual maturity
Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...
at 30–40 cm in length and around 2 years of age. It is a multiple
spawner, capable of reproducing up to 8 times per year, releasing up to 6 million eggs per year in captivity. Growth is well studied, with the fish reaching 194 mm in its first year, 340 mm in the second and 456 mm in the third year. The bluefin trevally is a popular target for both
commercial
Commercial may refer to:
* a dose of advertising conveyed through media (such as - for example - radio or television)
** Radio advertisement
** Television advertisement
* (adjective for:) commerce, a system of voluntary exchange of products and s ...
and
recreational fishermen. Commercial fisheries record up to 50
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s of the species taken per year in the west Indian Ocean, and around 700
lbs per year in
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 ...
. The rapid decimation of the Hawaiian population due to
overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...
has led to increased research in the
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...
potential of the species, with spawning achieved in captivity. Despite its popularity as a
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 ...
, many cases of
ciguatera
Ciguatera fish poisoning (CFP), also known simply as ciguatera, is a foodborne illness caused by eating reef fish whose flesh is contaminated with certain toxins. Such individual fish are said to be ciguatoxic. Symptoms may include diarrhea, vomi ...
poisoning have been reported from the species.
Taxonomy and phylogeny
The bluefin trevally is classified within the genus ''
Caranx
''Caranx'' is a genus of tropical to subtropical marine fishes in the jack family Carangidae, commonly known as jacks, trevallies and kingfishes. They are moderate- to large-sized, deep-bodied fishes which are distinguished from other carangid g ...
'', one of a number of groups known as the jacks or trevallies. ''Caranx'' itself is part of the larger jack and horse mackerel family
Carangidae
The Carangidae are a family of ray-finned fish which includes the jacks, pompanos, jack mackerels, runners, and scads. It is the largest of the six families included within the order Carangiformes. Some authorities classify it as the only family ...
, which in turn is part of the
order 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
A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...
by the famed French
naturalist Georges Cuvier
Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuvier ...
in 1833 based on specimens collected off Waigio,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
; one of 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 ...
.
He named the species ''Caranx melampygus'', placing the species in the jack genus ''Caranx'' which had been established by
Bernard Lacépède three decades previously. The name's
specific epithet
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
is derived from the Latin translation of "black spotted".
This is still currently considered the correct placement, however later authors placed in other now defunct genera (''Carangus'' and ''Carangichthys'') which has since been deemed incorrect, and the original classification stands.
The species was independently redescribed and named seven times after Cuvier's initial description, with all of these names assigned between 1836 and 1895. The names ''C. bixanthopterus'' and ''C. stellatus'' were often used in the literature, and were variably classed as
synonyms
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of ''C. melampygus'' or valid individual species after their naming. This confusion culminated in Yojiro Wakiya concluding in 1924 they should be treated as separate species.
The taxonomy of the species was finally revised by Frederick Berry in 1965, who resolved these two names as being synonymous with ''C. melampygus'', and placed several other names in synonymy with ''C. melampygus''.
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, these later names are deemed
junior synonym
The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently.
* In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...
s of ''C. melampygus'' and rendered invalid.
The species has not been included in any detailed
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
studies of the Carangidae.
The species is most
commonly referred to as the 'bluefin trevally', with the species's distinctive blue fins contributing to most of its other common names. These include bluefin jack, bluefin kingfish, blue ulua, omilu, bluefinned crevalle and spotted trevally. The species has many other non-English names due to its wide distribution.
Description
The bluefin trevally is a large fish, growing to a maximum known length of 117 cm and a weight of 43.5 kg,
however it is rare at lengths greater than 80 cm.
It is similar in shape to a number of other large jacks and trevallies, having an oblong, compressed body with the
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
profile slightly more convex than the
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...
profile, particularly
anteriorly. This slight convexity leads to the species having a much more pointed snout than most other members of ''Caranx''.
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 ...
is in two parts, the first consisting of 8
spines and the second of 1 spine followed by 21 to 24
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
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 2
anteriorly detached spines followed by 1 spine and 17 to 20 soft rays.
The
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 contain 1 spine and 20 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 se ...
is strongly forked, and the
pectoral 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 ...
s are falcate, being longer than the length of the head. 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 pronounced and moderately long anterior arch, with the curved section intersecting the straight section below the lobe of the second dorsal fin. The curved section of the lateral line contains 55-70
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 ...
while the straight section contains 0 to 10 scales followed by 27 to 42 strong
scute
A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
s. The chest is completely covered in scales.
The upper jaw contains a series of strong outer
canines with an inner band of smaller teeth, while the lower jaw contains a single row of widely spaced conical teeth. The species has 25 to 29
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 ...
s in total and there are 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 ...
present.
The eye is covered by a moderately weakly developed
adipose eyelid
An adipose eyelid is a transparent eyelid found in some species of fish, that covers some or all of the eye. They are most commonly found on deep sea (benthic) fish, but can also be seen on non-benthic fish. Fish with this feature include milkfish ...
, and the posterior extremity of the
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 ...
is vertically under or just past the anterior margin of the eye.
Despite their wide range, the only geographical variation in the species is the depth of the body in smaller specimens.
The upper body of the bluefin trevally is a silver-brassy colour, fading to silvery white on the underside of the fish, often with blue hues. After they reach lengths greater than 16 cm, blue-black spots appear on the upper flanks of the fish, with these becoming more prolific with age.
There is no dark spot on the
operculum. The species takes its name from the colour of its dorsal, anal and caudal fins, which are a diagnostic
electric blue. The pelvic and pectoral fins are white, with the pectoral fin having a yellow tinge. Juvenile fish do not have the bright blue fins, instead have dark fins with the exception of a yellow pectoral fin.
Some juvenile fish have also been recorded as having up to five dark vertical bars on their sides.
Distribution
![Caranx melampygus2](https://upload.wikimedia.org/wikipedia/commons/b/bd/Caranx_melampygus2.jpg)
The bluefin trevally is widely distributed, occupying 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 ...
and subtropical waters of the
Indian
Indian or Indians may refer to:
Peoples South Asia
* Indian people, people of Indian nationality, or people who have an Indian ancestor
** Non-resident Indian, a citizen of India who has temporarily emigrated to another country
* South Asia ...
and
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 ...
s, ranging along the coasts of four
continent
A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...
s and hundreds of smaller islands and
archipelago
An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands.
Examples of archipelagos include: the Indonesian Archi ...
s.
In the Indian Ocean, the species easternmost range is the coast of continental
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, being distributed from the southern tip of
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 ...
north along the east African coastline to the
Red Sea
The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...
and
Persian Gulf
The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...
. The species' range extends eastwards along the
Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
n coastline including
Pakistan
Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
,
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
and into
South East Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
, the
Indonesian Archipelago
The islands of Indonesia, also known as the Indonesian Archipelago ( id, Kepulauan Indonesia) or Nusantara, may refer either to the islands comprising the country of Indonesia or to the geographical groups which include its islands.
History ...
and northern
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 ...
.
The southernmost record from the west coast of Australia comes from
Exmouth Gulf
Exmouth Gulf is a gulf in the north-west of Western Australia. It lies between North West Cape and the main coastline of Western Australia. It is considered to be part of the Pilbara Coast and Northwest Shelf, and the Carnarvon Basin geologi ...
.
Elsewhere in the Indian Ocean, the species has been recorded from hundreds of small island groups including the
Maldives
Maldives (, ; dv, ދިވެހިރާއްޖެ, translit=Dhivehi Raajje, ), officially the Republic of Maldives ( dv, ދިވެހިރާއްޖޭގެ ޖުމްހޫރިއްޔާ, translit=Dhivehi Raajjeyge Jumhooriyyaa, label=none, ), is an archipelag ...
,
Seychelles
Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, V ...
,
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
and the
Cocos (Keeling) Islands
)
, anthem = "''Advance Australia Fair''"
, song_type =
, song =
, image_map = Australia on the globe (Cocos (Keeling) Islands special) (Southeast Asia centered).svg
, map_alt = Location of the Cocos (Keeling) Islands
, map_caption = ...
.
The bluefin trevally is abundant in the central Indo-Pacific region, found throughout all the archipelagos and offshore islands including Indonesia,
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
and
Solomon Islands
Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its capita ...
. Along continental Asia, the species has been recorded from
Malaysia
Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
to
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
and mainland
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
.
Its offshore range does extend north to
Hong Kong
Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China ( abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delt ...
,
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
and southern
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 ...
in the north western Pacific.
In the south, the species reaches as far south as
Sydney
Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...
in Australia.
Its distribution continues throughout the western Pacific including
Tonga
Tonga (, ; ), officially the Kingdom of Tonga ( to, Puleʻanga Fakatuʻi ʻo Tonga), is a Polynesian country and archipelago. The country has 171 islands – of which 45 are inhabited. Its total surface area is about , scattered over in ...
,
Western Samoa
Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands ( Savai'i and Upolu); two smaller, inhabited islands ( Manono and Apolima); a ...
and
Polynesia
Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...
, and the
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 ...
an Islands.
The easternmost limit of the species distribution is the
Mesoamerica
Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. W ...
n coastline between
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
and
Ecuador
Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...
in the central eastern Pacific,
including islands such as the
Galápagos Islands
The Galápagos Islands (Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...
.
Habitat
![Horsmakreel](https://upload.wikimedia.org/wikipedia/commons/9/91/Horsmakreel.JPG)
The bluefin trevally occurs in a wide range of
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 ...
and offshore marine settings throughout its range, including
estuarine
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
waters. The species is known to move throughout the water column; however is most often observed in a
demersal
The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...
setting, swimming not far from the seabed.
In the inshore environment, the species is present in almost all settings including bays,
harbour
A harbor (American English), harbour (British English; see spelling differences), or haven is a sheltered body of water where ships, boats, and barges can be docked. The term ''harbor'' is often used interchangeably with ''port'', which is a ...
s,
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
and rocky
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...
s,
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...
s, sand flats and
seagrass meadow
A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...
s.
Juveniles and subadults are more common in these settings, and prefer these more protected environments, where they live in water to a minimum of around 2 m depth.
Adults tend to prefer more exposed, deeper settings such as outer reef slopes, outlying
atoll
An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gr ...
s and bomboras, often near drop offs,
with the species reported from depths up to 183 m.
Adults often enter shallower
channel
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
s, reefs and lagoons to feed at certain periods during the day.
The bluefin trevally displays some habitat partitioning with
giant trevally
The giant trevally (''Caranx ignobilis''), also known as the lowly trevally, barrier trevally, ronin jack, giant kingfish or ''ulua'', is a species of large marine fish classified in the jack family, Carangidae. The giant trevally is distributed ...
, ''Caranx ignobilis'', tending to be more common outside the major bays than their relatives.
Juvenile and subadult bluefin trevally have been recorded in estuaries in several locations,
and generally occupy large, open estuaries up to the middle reaches of the system. These estuaries are often lined by mudflats and
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
s, however the species rarely enters these shallow waters.
Individuals of between 40 and 170 mm have been recorded in South African estuaries, where they are the least tolerant carangid to the
brackish
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
and freshwater conditions of these systems. Bluefin trevally can tolerate
salinities
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
of between 6.0 and 35 ‰, and only occupy clear, low
turbidity
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
Fluids can ...
waters. There is evidence the species is only resident in these estuaries for short periods.
The species is also absent from coastal lakes that many other carangids are known from.
Biology and ecology
![A pair of omilu or blue trevally (6741932671)](https://upload.wikimedia.org/wikipedia/commons/9/98/A_pair_of_omilu_or_blue_trevally_%286741932671%29.jpg)
The bluefin trevally is a
schooling
A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes compuls ...
species as a juvenile, transitioning to a more solitary fish with well defined
home range
A home range is the area in which an animal lives and moves on a periodic basis. It is related to the concept of an animal's territory which is the area that is actively defended. The concept of a home range was introduced by W. H. Burt in 1943. He ...
s as an adult.
Adults do school to form
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 aquati ...
aggregations or temporarily while hunting, with evidence from laboratory studies indicates bluefin trevally are able to coordinate these aggregations over
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Co ...
s based on the release of
dimethylsulfoniopropionate
Dimethylsulfoniopropionate (DMSP), is an organosulfur compound with the formula (CH3)2S+CH2CH2COO−. This zwitterionic metabolite can be found in marine phytoplankton, seaweeds, and some species of terrestrial and aquatic vascular plants ...
(DMSP) from the reef. DMSP is a naturally occurring chemical produced by
marine algae
Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it al ...
and to a lesser extent
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
s and their symbiotic
zooxanthellae
Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Sy ...
. The number of fish present in an area is also influenced by
tidal
Tidal is the adjectival form of tide.
Tidal may also refer to:
* ''Tidal'' (album), a 1996 album by Fiona Apple
* Tidal (king), a king involved in the Battle of the Vale of Siddim
* TidalCycles, a live coding environment for music
* Tidal (servic ...
factors and possibly the abundance of
prey
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 the ...
and other environmental factors.
Tracking studies in Hawaii have found bluefin trevally
patrol
A patrol is commonly a group of personnel, such as Law enforcement officer, law enforcement officers, military personnel, or Security guard, security personnel, that are assigned to monitor or secure a specific geographic area.
Etymology
Fro ...
back and forth along a home range of patch reef walls during the day, only stopping for variable periods where major depth changes or discontinuities in the reef were present. Several fish patrol the same reef patch, reversing direction where the others do. While most fish patrol the one reef, some have been observed to make excursions to nearby reefs, before returning to their home reef later.
Night
Night (also described as night time, unconventionally spelled as "nite") is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends o ...
time movements are less extensive than daytime movements, with the trevally moving rapidly between several small reef sections, before slowing down and milling in one patch for around an hour. The fish living in a particular region congregate in one area at night, before returning to their individual daytime range during the day. The reason for this congregation is unclear, but may be important to the social structure of the species.
Long term studies have found the fish may range up to 10.2 km over several months, however, is much less restricted in its movements than its relative, the giant trevally. A Hawaiian
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
study found the species to be one of the most abundant large
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 ...
s in the islands, however it is less abundant in the heavily exploited Main Hawaiian Islands compared to the remote Northwest Hawaiian Islands. The main difference in these populations was the relative lack of large adult fish in the inhabited areas compared to the remote, unfished regions.
A study on carangids caught during a
fishing tournament
A fishing tournament, or derby, is an organised competition among anglers. Fishing tournaments typically take place as a series of competitive events around or on a clearly defined body of water with specific rules applying to each event. They can ...
in Hawaii found the bluefin trevally is the most common trevally species taken, accounting for over 80% of the carangid catch. The authors note that this may not only reflect its abundance, but also it vulnerability to specific fishing methods used in the tournament.
Apart from the typical predator-prey relationship the species shows (described later), an individual of the species has been seen to rub itself against the skin of a
Galapagos shark
The Galapagos shark (''Carcharhinus galapagensis'') is a species of requiem shark, in the family Carcharhinidae, found worldwide. It favors clear reef environments around oceanic islands, where it is often the most abundant shark species. A larg ...
, apparently to rid itself of
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s. This behaviour is also observed in
rainbow runner
The rainbow runner (''Elagatis bipinnulata''), also known as the rainbow yellowtail, Spanish jack and Hawaiian salmon, is a common species of pelagic ocean, marine fish of the jack family, Carangidae. The species is widespread throughout the tropi ...
and is a rare example of a commensal cleaner relationship where the cleaner does not gain anything.
Diet and feeding
![Moofushi Kandu fish](https://upload.wikimedia.org/wikipedia/commons/3/32/Moofushi_Kandu_fish.jpg)
The bluefin trevally is a fast swimming, mainly
piscivorous
A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...
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 ...
which shows a wide range in hunting techniques.
Two studies of adult fish in Hawaii found fish to be the dominant food type in the species, making up over 95% volume of the stomach contents by weight.
Here the main fish selected were small reef dwellers, with fish from the families
Labridae,
Mullidae
The goatfishes are perciform fish of the family Mullidae. The family is also sometimes referred to as the red mullets, which also refers more narrowly to the genus ''Mullus''.
The family name and the English common name mullet derived from Lati ...
,
Scaridae and
Priacanthidae
The Priacanthidae, the bigeyes, are a family of 18 species of marine ray-finned fishes. " Catalufa" is an alternate common name for some members of the Priacanthidae. The etymology of the scientific name (, to bite + , thorn) refers to the fam ...
being the most common. Despite the preference of several families, bluefin trevally do take a very wide variety of fish in small amounts, including various species of
eel
Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...
.
The species appears to have a preference for fish of a specific size, which depends on its own length and age.
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 (mainly
octopus
An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...
or
squid
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...
)
and a wide array of crustaceans are also taken in smaller quantities, with
shrimp
Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...
s,
stomatopod
Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in leng ...
s and
crab
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
s being the most common.
The diet of juveniles in Hawaiian and South African estuaries has also been determined, with these younger fish having a more crustacean based diet than the adults.
In Hawaii, crustaceans make up 96% of the gut contents numerically, with
tanaid
The crustacean order Tanaidacea (known as tanaids) make up a minor group within the class Malacostraca. There are about 940 species in this order.
Description
Tanaids are small, shrimp-like creatures ranging from in adult size, with most speci ...
s and
isopod
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
s dominating the diet, while fish only make up 4% numerically.
Juveniles less than 170 mm in South African estuaries feed predominantly on
mysid
Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in thi ...
s and paenid
prawn
Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten.
The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...
s, before shifting to a more fish based diet at larger sizes. Small fish are able to effectively filter these small crustaceans from the water, while adults are not.
In both cases, a transition to a more fish based diet with age was found to occur, although the length at which this transition occurred varied between location.
The diet overlap with the similar ''C. ignobilis'' is low in the Hawaiian Islands, suggesting there is some separation of feeding niches.
Calculations suggest each individual bluefin trevally consumes around 45 kg of fish per year on average, making it one of the most effective predators in this habitat.
The bluefin trevally displays a remarkable array of hunting techniques, ranging from midwater attacks to ambush and taking advantage of larger
forage fish
Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food ...
. The species is reported to hunt during the day, particularly at
dawn
Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's horizo ...
and
dusk
Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enou ...
in most locations;
however it is known to be a
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
feeder in South Africa.
The bluefin trevally hunts both as a solitary individual and in groups of up to 20, with most fish preferring an individual approach.
In groups, these fish will rush their prey, and disperse the school, allowing for isolated individuals to be picked out and eaten,
much in the way the related species, giant trevally have been observed to do in captivity. In some cases, only one individual in a group will attack the prey school. Where the prey is schooling
reef fishes, once the prey school has been attacked, the trevally chases down the prey as they scatter back to cover in the corals, often colliding with coral as they attempt to snatch a fish.
While hunting in midwater, fish swim both against and with the
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide t ...
, although significantly more fish hunt when swimming with the tide (i.e. 'downstream'), suggesting some mechanical advantage is gained when hunting in this mode.
Another method of attack is
ambush
An ambush is a long-established military tactics, military tactic in which a combatant uses an advantage of concealment or the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbru ...
; in this mode the trevally change their colour to a dark
pigmentation
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
state and hide behind large coral lumps close to where the aggregations (often spawning reef fish) occur.
Once the prey is close enough to the hiding spot, the fish ram the base of the school, before chasing down individual fish. These dark fish in ambush mode vigorously drive away any other bluefin trevally that stray too close to the aggregation.
Ambushes have also been observed on small midwater planktivorous fishes are moving to or from the shelter of the reef.
In many cases, the species uses changes in the depth of the reef such as ledges to conceal its ambush attacks. Bluefin trevally also enter lagoons as the tide rises to hunt small
baitfish
300px, Feeder Goldfish are common baitfish.
Bait fish (or baitfish) are small-sized fish caught and used by anglers as bait to attract larger predatory fish, particularly game fish. Baitfish species are typically those that are common and bree ...
in the shallow confines, leaving as the tide falls.
The species is also known to follow large
rays
Ray may refer to:
Fish
* Ray (fish), any cartilaginous fish of the superorder Batoidea
* Ray (fish fin anatomy), a bony or horny spine on a fin
Science and mathematics
* Ray (geometry), half of a line proceeding from an initial point
* Ray (gra ...
,
shark
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...
s and other foraging fish such as
goatfish
The goatfishes are perciform fish of the family Mullidae. The family is also sometimes referred to as the red mullets, which also refers more narrowly to the genus ''Mullus''.
The family name and the English common name mullet derived from Lati ...
and
wrasse
The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 81 genera, which are divided into 9 subgroups or tribes.
They are typically small, most of them le ...
around sandy substrates, waiting to pounce on any disturbed crustaceans or fish which are flushed out by the larger fish.
Life history
![Bluefin trevally pair](https://upload.wikimedia.org/wikipedia/commons/4/41/Bluefin_trevally_pair.jpg)
The bluefin trevally reaches
sexual maturity
Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...
at between 30 and 40 cm in length and around 2 years in age,
with one study Hawaii suggesting maturation occurs at a length of around 35 cm on average.
There is also a difference in the length at maturation between the two
sexes
Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones ( ova, of ...
, with females on average reaching maturity at 32.5 cm length, while males attain maturity at 35 cm on average.
Sex ratio
The sex ratio (or gender ratio) is usually defined as the ratio of males to females in a population. As explained by Fisher's principle, for evolutionary reasons this is typically about 1:1 in species which reproduce sexually. Many species devia ...
s in the species vary by location with population off east Africa being skewed towards males (M:F = 1.68:1),
while in Hawaii the opposite is true with the M:F ratio being 1:1.48.
The period of the year over which
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 aquati ...
occurs is also variable by location, with African fish reproducing between September and March
while in Hawaii this occurs between April and November, with a peak in May to July.
Natural spawning behaviour in the species has never been observed,
although large aggregations of bluefin trevally observed in
Palau
Palau,, officially the Republic of Palau and historically ''Belau'', ''Palaos'' or ''Pelew'', is an island country and microstate in the western Pacific. The nation has approximately 340 islands and connects the western chain of the Caro ...
consisting of over 1000 fish are believed to be for the purpose of spawning.
Extensive studies on the species in captivity has revealed the species to be a multiple spawner, capable of spawning at least 8 times a year, and up to twice in 5 days.
Spawning events are often clustered in a few consecutive or alternate days, usually in the third or fourth
lunar phase
Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...
s. Spawning apparently occurs at night to minimise predation on
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s.
Fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
in the natural environment has been reported to range from around 50 000 to 4 270 000, with larger individuals releasing more eggs.
Studies in captive fish show females may produce over 6 000 000 eggs per year. These eggs are
pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...
and spherical, with
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
s between 0.72 and 0.79 mm.
The development of the bluefin trevally
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
after hatching has been briefly described in a study of changes in the
digestive enzyme
Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anim ...
s of the species. The species has depleted its storage of energy from the egg at 3 days old, with a series of transformations including coiling of the gut and fin formation occurring before
flexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...
at 26 days of age.
Digestive enzymes active from hatching to 30 days old show an apparent shift from
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
utilisation to
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
and
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
utilisation as the larvae grows older.
Measurements from juveniles in Hawaii indicate the fish is around 70 mm by 100 days and 130 mm by 200 days.
Otolith data fitted to the von Bertalanffy growth curve shows the species grows to 194 mm in its first year, 340 mm in the second and 456 mm in the third year. It reaches 75 cm by 8 years of age and 85 cm by 12 years.
This model also suggests a growth of 0.45 mm/day; while laboratory feeding studies found the fish grow at an average of 0.4 mm/day in these confined conditions.
The maximum theoretical size indicated from the growth curves is 89.7 cm,
much less than the 117 cm reported as the known maximum size.
Juveniles often enter estuaries, however the species is not estuary dependent as breeding is known to occur where no estuaries are present, suggesting the use of these habitats is
facultative
{{wiktionary, facultative
Facultative means "optional" or "discretionary" (antonym '' obligate''), used mainly in biology in phrases such as:
* Facultative (FAC), facultative wetland (FACW), or facultative upland (FACU): wetland indicator statuses ...
. The fish move from these shallower inshore waters to deeper reefs as they grow.
Two
hybrid
Hybrid may refer to:
Science
* Hybrid (biology), an offspring resulting from cross-breeding
** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species
** Hybridity, the property of a hybrid plant which is a union of two dif ...
isation events in the species are known from Hawaii; the first with the giant trevally, ''Caranx ignobilis'' and the second with the
bigeye trevally
The bigeye trevally (''Caranx sexfasciatus''), also known as the bigeye jack, great trevally, six-banded trevally and dusky jack, is a species of widespread large marine fish classified in the jack family Carangidae. The bigeye trevally is distr ...
, ''Caranx sexfasciatus''. Both were initially identified as hybrids by intermediate physical characteristics, and were later confirmed by
DNA sequencing
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...
.
It has been suggested these hybrids resulted from mixed species schooling during spawning periods. It is thought that hybridisation is more likely if one or both parent species is rare in an area, which is the case in much of the Main Hawaiian Islands, where
overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...
has severely depleted all trevally species populations.
Relationship to humans
![Bluefin trevally trio](https://upload.wikimedia.org/wikipedia/commons/4/4e/Bluefin_trevally_trio.jpg)
The bluefin trevally is an important species to both commercial
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 ...
and
angler
Angler may refer to:
* A fisherman who uses the fishing technique of angling
* ''Angler'' (video game)
* The angler, ''Lophius piscatorius'', a monkfish
* More generally, any anglerfish in the order Lophiiformes
* '' Angler: The Cheney Vice Pres ...
s, with the popularity of the fish leading to extensive
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...
trials. The catch statistics for the bluefin trevally are poorly reported in most of its range, with only parts of the western Indian Ocean supplying information to the
FAO
The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
. In this region, catch levels have fluctuated between 2 and 50
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s in the past decade.
Hawaii also keeps catch records, with these showing the species is taken in far less numbers than the giant trevally, with only 704 pounds taken compared to 10 149 lbs of giant trevally in 1998.
In Hawaii, the nearshore stocks of the species have been in decline since the early 1900s, with commercial landings dropping over 300% from 1990 to 1991, and have not recovered.
Most bluefin trevally sold in Hawaii are now imported from other Indo-Pacific nations.
The species is taken by a variety of
netting
In law, set-off or netting are legal techniques applied between persons or businesses with mutual rights and liabilities, replacing gross positions with net positions. It permits the rights to be used to discharge the liabilities where cross cla ...
and trapping methods, as well and by hook and line in commercial fisheries. It is usually sold fresh, as well as frozen or
salted.
The rapid decline in the population has seen a focus on breeding the bluefin trevally in captivity. The species' aquaculture potential was first investigated in a 1975 experiment in
French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
, where juveniles of the species were caught in the wild and transported back to a laboratory. The study found the fish grew to a commercial size of 300 g in 6 to 8 months and only suffered a 5%
mortality rate
Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...
. It was concluded that such a technique carried out on a larger scale in lagoons would be promising due to the growth rate and relatively high price commanded by the species at
market
Market is a term used to describe concepts such as:
*Market (economics), system in which parties engage in transactions according to supply and demand
*Market economy
*Marketplace, a physical marketplace or public market
Geography
*Märket, an ...
. Further investigations into the potential for offshore aquaculture were conducted in Hawaii, where the species successfully spawned in captivity.
The only barrier in these studies to successful production was problems with commercial food items. An
in vitro
''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...
cell culture
Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...
has recently been established for the species, which will allow long term management of potential
viral disease
A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.
Structural Characteristics
Basic structural characteristics, s ...
s that may arise during aquaculture of the fish. The bluefin trevally has been successfully kept in large saltwater aquaria, but require large water volumes to adapt well.
The bluefin trevally is one of the premier
gamefish
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 ...
of the Indo-Pacific region, although is often overshadowed by its larger cousin, the giant trevally.
The fish makes long powerful runs on light tackle, and is a determined fighter.
The species readily accepts both
bait and
lures, with live fish or squid often used as bait and a variety of lures also used on the species. Lures may include poppers, plugs, spoons, jigs, soft plastic lures and even
saltwater flies.
The species inshore habits make it a popular target for
spearfishermen also.
In Hawaii the species has bag and size limit restrictions in place to prevent further
overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...
.
It is considered to be a good to excellent
food fish
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingest ...
, however many cases of
ciguatera
Ciguatera fish poisoning (CFP), also known simply as ciguatera, is a foodborne illness caused by eating reef fish whose flesh is contaminated with certain toxins. Such individual fish are said to be ciguatoxic. Symptoms may include diarrhea, vomi ...
poisoning have been attributed to the bluefin trevally.
Laboratory tests have confirmed the presence of the toxin in the species flesh, with fish greater than 50 cm likely to be a carrier.
The risk of poisoning has also affected the sales of the fish in the marketplace in recent years.
Also of concern is one report of infection by a
dracunculoid parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
while preparing the fish for eating. In this case, the parasite invaded the victim's body by entering an open
wound
A wound is a rapid onset of injury that involves laceration, lacerated or puncture wound, punctured skin (an ''open'' wound), or a bruise, contusion (a ''closed'' wound) from blunt force physical trauma, trauma or compression. In pathology, a '' ...
while he was
fillet
Fillet may refer to:
*Annulet (architecture), part of a column capital, also called a fillet
*Fillet (aircraft), a fairing smoothing the airflow at a joint between two components
*Fillet (clothing), a headband
*Fillet (cut), a piece of meat
*Fille ...
ing the species, and is believed to be one of the first records for such cross contamination. The
IGFA
The International Game Fish Association (''IGFA'') is the leading authority on angling pursuits and the keeper of the most current World Record fishing catches by fish categories. Fishermen who are sport fishers are careful to follow their string ...
maintains full line and ripped class records for the bluefin trevally. The all tackle world record for the species stands at 13.24 kg (29 lb 3oz) taken off
Clipperton Island
Clipperton Island ( or ; ) is an uninhabited, coral atoll in the eastern Pacific Ocean. It is from Paris, France, from Papeete, Tahiti, and from Mexico. It is an Overseas France, overseas state private property of France under direct authori ...
in 2012.
References
External links
IGFA species recordsBluefin trevally (''Caranx melampygus'')a
FishBaseBluefin trevally (''Caranx melampygus'')a
Australian Museum Onlinea
Mexfisha
Reel1in*
{{Taxonbar, from=Q2282919
bluefin trevally
The bluefin trevally (''Caranx melampygus''), also known as the bluefin jack, bluefin kingfish, bluefinned crevalle, blue ulua, omilu, and spotted trevally), is a species of large, widely distributed marine fish classified in the jack family, Ca ...
Fish of the Indian Ocean
Fish of the Pacific Ocean
Fish described in 1833, bluefin trevally
Taxa named by Georges Cuvier, bluefin trevally