Shadow trevally
Encyclopedia
The shadow trevally, Carangoides dinema (also known as the shadow kingfish, twothread trevally and Aldabra trevally) is a species
of inshore marine
fish
in the jack family Carangidae
. The species is patchily distributed throughout the tropical and subtropical waters of the Indian
and west Pacific Ocean
s, from South Africa
in the west to Japan
and Samoa
in the east, reaching as far south as Indonesia
and New Caledonia
. It is most easily distinguished from similar species by as series of dark rectangular blotches under the second dorsal fin
, giving a 'shadowed' appearance, from which its common name
is derived. The shadow trevally is a reasonably large fish, growing to 85 cm in length and at least 2.6 kg in weight. It inhabits shallow coastal waters including reef
s, bay
s and estuaries, where it takes small fish and benthic crustacean
s as prey. Nothing is known of the species ecology
and reproductive biology
. It is of little importance to fisheries, and is occasionally taken by bottom trawls and other artisanal fishing gear.
Carangoides
, one of a number of groups of fish referred to as jacks and trevallies. Carangoides is further classified in the family Carangidae
, itself part of the suborder Percoidei
and the order Perciformes
; the perch-like fishes.
The species
was first scientifically described and named by the Dutch ichthyologist Pieter Bleeker
in 1851 based on a specimen collected from the waters off Jakarta
, located on Java
in Indonesia
, which was designated to be the holotype
. He named this new species Carangoides dinema, with the specific name derived from the Latin dis, meaning two and the Greek nema, meaning thread, referring to the fin anatomy of the species. This classification in Carangoides is still currently considered to be correct, although other authors have at times transferred the species to Caranx
and Carangichthys. The species was independently renamed once by David Starr Jordan
and Alvin Seale in 1908, who applied the name Caranx deani to the species. This later naming is considered invalid under the ICZN
nomenclature rules and is rendered a junior synonym. The species is quite unique in the comparatively simple taxonomic history
it has, with other related species often renamed and transferred between genera many times. The species is most commonly termed
the 'shadow trevally' or 'shadow kingfish' in reference to a series of small dark blotches positioned on the upper side, underneath the second dorsal fin, giving the appearance of shadow from the fin itself. Other names used for the species include 'twothread trevally' and 'Aldabra trevally'.
. The dorsal profile is strongly convex, while the ventral profile is less so, even tending to be concave between the snout and the anal fin, while the nape
is elevated and almost straight in profile. There are two separate dorsal fin
s, the first consisting of 8 spines and second of a single spine and 17 to 19 soft rays. The lobe of the second dorsal fin is elongated, being greater than the head length. The anal fin is composed of two anteriorly detached spines followed by a single spine and 15 to 17 soft rays. The lateral line
has a moderate arch anteriorly, with the junction of the curved and straight sections below the tenth or twelfth soft rays of the second dorsal fin. The curved section of the lateral line is slightly longer than the straight section, and contains 60 to 63 scales
, while the straight part contains 0 to 6 scales followed by 23 to 30 scutes. The breast is devoid of scales ventrally to behind the pelvic fin origin and up to the pectoral fin base, although in rare cases this is interrupted by a lateral band of scales. Both jaw
s contain bands of small teeth, with the bands becoming wider anteriorly, and the upper jaw also has an irregular outer series of moderately large teeth, with large specimens also showing this in the lower jaw. There are a total of 24 to 28 gill raker
s and 24 vertebrae.
In life, the shadow trevally is a blush green colour above, fading to a silvery white on the underside. It takes its common name from a series of small black-brown rectangular blotches which become larger posteriorly on its back between the bases of the second dorsal fin rays. There is also a dark brown diffuse blotch present on the operculum
. The spinous dorsal fin is pale to dusky, while the second dorsal fin lobe is dusky with the ray tips yellowish. The anal fin has a distal margin which is whitish blue, the caudal fin has a yellowish upper lobe and pale trailing edges and lower lobe tip. The pectoral fins are hyaline
and the pelvic fins are whitish to dusky.
and west Pacific Ocean
s. The species westernmost limit is a section of the east Africa
n coast from South Africa
to Tanzania
. No records exist for the species further north until India
and Sri Lanka
. In the Pacific, the species is known from China
, Korea
, South East Asia and the Indonesia
n and Philippines
island chains. Its eastern most limit extends to Taiwan
and Japan
in the north and a number of small island groups including Tonga
and Samoa
in the south.
The shadow trevally inhabits coastal waters in depths generally less than 15 m. It is known to cruise in small schools along the shallow edge of steep reef
drop-offs, and has also been recorded from bay
s and estuaries. The species has been recorded around shipwreck
s, and one study showed it was one of the first fish to move in after a ship was scuttled.
of the shadow trevally is extremely poorly known. It is known to live either in small schools or individually, and is a predatory fish, taking small fish and benthic crustacean
s. Nothing is known of its movements or reproduction.
The shadow trevally is of little importance to fisheries throughout its range, taken as bycatch
and generally not distinguished from other carangid species. It is often taken by bottom trawls and various kinds of artisanal fishing gear.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of inshore marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate 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...
in the jack family Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
. The species is patchily distributed throughout the tropical and subtropical waters of the Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and west Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s, from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
in the west to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Samoa
Samoa
Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...
in the east, reaching as far south as Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
and New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
. It is most easily distinguished from similar species by as series of dark rectangular blotches under the second dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, giving a 'shadowed' appearance, from which its common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
is derived. The shadow trevally is a reasonably large fish, growing to 85 cm in length and at least 2.6 kg in weight. It inhabits shallow coastal waters including reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s and estuaries, where it takes small fish and benthic crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s as prey. Nothing is known of the species ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
and reproductive biology
Reproductive biology
Reproductive biology is a study mainly involving the reproductive system and sex organs. It is closely related to reproductive endocrinology and infertility. also is miotosis and miosis...
. It is of little importance to fisheries, and is occasionally taken by bottom trawls and other artisanal fishing gear.
Taxonomy and naming
The shadow trevally is classified within the genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Carangoides
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 in the genus Caranx...
, one of a number of groups of fish referred to as jacks and trevallies. Carangoides is further classified in the family Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
, itself part of the suborder Percoidei
Percoidei
Percoidei is one of eighteen suborders of bony fish in the order Perciformes. Many commercially harvested fish species are contained in this suborder, including the snappers, jacks, whitings, groupers, bass, perches and porgies.-Divisions:...
and the order Perciformes
Perciformes
The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
; the perch-like fishes.
The species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
was first scientifically described and named by the Dutch ichthyologist Pieter Bleeker
Pieter Bleeker
Pieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
in 1851 based on a specimen collected from the waters off Jakarta
Jakarta
Jakarta is the capital and largest city of Indonesia. Officially known as the Special Capital Territory of Jakarta, it is located on the northwest coast of Java, has an area of , and a population of 9,580,000. Jakarta is the country's economic, cultural and political centre...
, located on Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, which was designated to be the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
. He named this new species Carangoides dinema, with the specific name derived from the Latin dis, meaning two and the Greek nema, meaning thread, referring to the fin anatomy of the species. This classification in Carangoides is still currently considered to be correct, although other authors have at times transferred the species to Caranx
Caranx
Caranx is a genus of tropical to subtropical marine fish 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 genera by specific gill raker, fin ray and dentition...
and Carangichthys. The species was independently renamed once by David Starr Jordan
David Starr Jordan
David Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
and Alvin Seale in 1908, who applied the name Caranx deani to the species. This later naming is considered invalid under the ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
nomenclature rules and is rendered a junior synonym. The species is quite unique in the comparatively simple taxonomic history
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
it has, with other related species often renamed and transferred between genera many times. The species is most commonly termed
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
the 'shadow trevally' or 'shadow kingfish' in reference to a series of small dark blotches positioned on the upper side, underneath the second dorsal fin, giving the appearance of shadow from the fin itself. Other names used for the species include 'twothread trevally' and 'Aldabra trevally'.
Description
The shadow trevally is similar in form to a number of other jacks in the family Carangidae, having an almost ovate, strongly compressed body. It is fairly large fish, growing to a maximum known length of 85 cm and a recorded weight of 2.6 kgKilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
. The dorsal profile is strongly convex, while the ventral profile is less so, even tending to be concave between the snout and the anal fin, while the nape
Nape
The nape is the back of the neck. In technical anatomical/medical terminology, the nape is referred to by the word nucha, which also gives the adjective corresponding to "nape" in English, "nuchal"....
is elevated and almost straight in profile. There are two separate dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s, the first consisting of 8 spines and second of a single spine and 17 to 19 soft rays. The lobe of the second dorsal fin is elongated, being greater than the head length. The anal fin is composed of two anteriorly detached spines followed by a single spine and 15 to 17 soft rays. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
has a moderate arch anteriorly, with the junction of the curved and straight sections below the tenth or twelfth soft rays of the second dorsal fin. The curved section of the lateral line is slightly longer than the straight section, and contains 60 to 63 scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
, while the straight part contains 0 to 6 scales followed by 23 to 30 scutes. The breast is devoid of scales ventrally to behind the pelvic fin origin and up to the pectoral fin base, although in rare cases this is interrupted by a lateral band of scales. Both jaw
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 serving to open and close it and is part of the body plan of...
s contain bands of small teeth, with the bands becoming wider anteriorly, and the upper jaw also has an irregular outer series of moderately large teeth, with large specimens also showing this in the lower jaw. There are a total of 24 to 28 gill raker
Gill raker
Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch and are involved with filter feeding tiny prey. They are not to be confused with the gill filaments that compose the bony part of the gill. Rakers are usually present in two rows, projecting from both the...
s and 24 vertebrae.
In life, the shadow trevally is a blush green colour above, fading to a silvery white on the underside. It takes its common name from a series of small black-brown rectangular blotches which become larger posteriorly on its back between the bases of the second dorsal fin rays. There is also a dark brown diffuse blotch present on the operculum
Operculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
. The spinous dorsal fin is pale to dusky, while the second dorsal fin lobe is dusky with the ray tips yellowish. The anal fin has a distal margin which is whitish blue, the caudal fin has a yellowish upper lobe and pale trailing edges and lower lobe tip. The pectoral fins are hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
and the pelvic fins are whitish to dusky.
Distribution and habitat
The shadow trevally is distributed patchily throughout the tropical to subtropical waters of the IndianIndian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and west Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s. The species westernmost limit is a section of the east Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
n coast from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
. No records exist for the species further north until India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
. In the Pacific, the species is known from China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
, South East Asia and the Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
n and Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
island chains. Its eastern most limit extends to Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
in the north and a number of small island groups including Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
and Samoa
Samoa
Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...
in the south.
The shadow trevally inhabits coastal waters in depths generally less than 15 m. It is known to cruise in small schools along the shallow edge of steep reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
drop-offs, and has also been recorded from bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s and estuaries. The species has been recorded around shipwreck
Shipwreck
A shipwreck is what remains of a ship that has wrecked, either sunk or beached. Whatever the cause, a sunken ship or a wrecked ship is a physical example of the event: this explains why the two concepts are often overlapping in English....
s, and one study showed it was one of the first fish to move in after a ship was scuttled.
Biology and fishery
The biology and ecologyEcology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
of the shadow trevally is extremely poorly known. It is known to live either in small schools or individually, and is a predatory fish, taking small fish and benthic crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. Nothing is known of its movements or reproduction.
The shadow trevally is of little importance to fisheries throughout its range, taken as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
and generally not distinguished from other carangid species. It is often taken by bottom trawls and various kinds of artisanal fishing gear.