Island trevally
Encyclopedia
The island trevally, Carangoides orthogrammus (also known as the island jack, thicklip trevally and false bluefin trevally), is a widespread 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...

 of offshore 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 classified 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 island trevally is common through the tropical regions 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 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, ranging from Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 and the Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....

 in the west to Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

 and the Revillagigedo Islands
Revillagigedo Islands
The Revillagigedo Islands or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem...

 in the central and eastern Pacific. The species is almost completely absent from the continental shelves, instead inhabiting offshore
Shore
A shore or 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 and present, while the beach is at the edge of the shore,...

 islands where it is found in lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

s and on reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

 systems. It is a moderately large fish, growing to a maximum recorded length of 75 cm and 6.6 kg in weight, and is distinguishable by its angular snout and yellow spots, as well as more detailed anatomical features. The island trevally often moves in small schools, preying on a variety of small fishes and 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. It is of moderate importance to fisheries throughout its range, often taken by trawls
Trawling
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....

, hook and line and various inshore netting methods, and is sold fresh or salted
Salting (food)
Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...

 at market.

Taxonomy and naming

The island trevally is classified within the genus 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...

, a group of fish commonly called jacks and trevallies. Carangoides falls into the jack and horse mackerel 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 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...

, in 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:...

.

The species was first scientifically described by the American ichthyologists 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 Gilbert
Charles Henry Gilbert
Charles Henry Gilbert was a pioneer ichthyologist and fishery biologist of particular significance to natural history of the western United States. He collected and studied fishes from Central America north to Alaska and described many new species...

 in 1881 based on a specimen taken from the Revillagigedo Islands
Revillagigedo Islands
The Revillagigedo Islands or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem...

, 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...

. They named this new species Caranx orthogrammus, placing the species in a closely related genus of jacks
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...

, but this was later changed to Carangoides after further revision of the family had occurred. The species was independently redescribed a named a number of times, with the fish placed in subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 status twice. John Treadwell Nichols
John Treadwell Nichols
John Treadwell Nichols was an American ichthyologist.-Biography:Nichols was born as son of John White Treadwell Nichols in Jamaica Plain, Boston, Massachusetts. In 1906 he studied vertebrate zoology at Harvard College where he graduated to Bachelor of Arts...

 considered his C. ferdau jordani to be separate to C. orthogrammus, or possibly a subspecies of the blue trevally
Blue trevally
The blue trevally, Carangoides ferdau is a common widespread species of pelagic marine fish classified in the jack family, Carangidae...

, Carangoides ferdau, and was later treansferred to Carangoides jordani. It was also considered a subspecies of a synonym the bludger
Bludger (fish)
The bludger, Carangoides gymnostethus , is a widespread species of large marine fish in the jack family, Carangidae...

, Carangoides gymnostethoides, and was also renamed as Carangoides nitidus. The fish is now considered a separate species, with the subspecies names and the later names rendered 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...

 naming rules. The species is commonly known
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...

 as 'island trevally' in reference to its preferred offshore habitat, with the names 'thicklip trevally' and 'false bluefin trevally' also used as descriptive names. The specific epithet means "straight lined" in Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

.

Description

The island trevally is a moderately large fish, growing to a maximum recorded length of 75 cm and 6.61 kg in weight. The species is quite similar to Carangoides ferdau, although the prominent yellow spots serve as a quick identifying feature. The island trevally has a compressed oblong
Rectangle
In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle...

 shaped body with the dorsal profile more convex than the ventral profile and the snout usually being slightly rounded. The 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...

 is in two sections, the first consisting of 8 spines and the second of 1 spine and 28 to 31 soft rays, with the lobe of the second dorsal fin being slightly falcate in younger individuals, but is always shorter than the head length. The anal fin has 2 detached spines followed by 1 spine attached to 24 to 26 soft rays, while the pelvic fin has 1 spine attached to 21 or 22 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 very slight anterior arch, with the intersection of the straight and curved sections between the 15th to 19th soft ray of the dorsal fin. The curved section contains 96 to 106 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 section contains 20 to 30 scales and 21 to 28 scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...

s. The breast is scaleless ventrally until the origin of pelvic fins, often with a small patch of pre-pelvic scales. Laterally, this naked area of the breast is separated from the naked base of the pectoral fins by a moderate band of scales. The lips are notably fleshy in adults, with both jaws containing narrow bands of villiform teeth which become obsolescent with age. There are 28 to 32 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 in total and 24 vertebrae.

The island trevally is a pale blue green above, becoming more silvery below, with adults having several quite large elliptical yellow to brassy spots scattered on their body close to the midline. There may be 9 or 10 dark vertical bars on the body from the head to the caudal peduncle. The soft dorsal, anal and caudal fins are a pale brownish to brilliant blue, with all other fins being pale green to 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...

 in colour.

Distribution and habitat

The island trevally is distributed throughout the offshore
Shore
A shore or 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 and present, while the beach is at the edge of the shore,...

 waters of the tropical and subtropical regions 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 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. In the Indian Ocean, it ranges from Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 on the east coast of Africa north to the Gulf of Aden
Gulf of Aden
The Gulf of Aden is located in the Arabian Sea between Yemen, on the south coast of the Arabian Peninsula, and Somalia in the Horn of Africa. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb strait, which is about 20 miles wide....

, but has not been recorded 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...

. Its range extends throughout South East Asia, 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 northern Australia
Northern Australia
The term northern Australia is generally known to include two State and Territories, being Queensland and the Northern Territory . The part of Western Australia north of latitude 26° south—a definition widely used in law and State government policy—is also usually included...

 in the eastern Indian Ocean. In the Pacific Ocean, the species has been recorded from 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...

, 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...

, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

 and the Revillagigedo Islands
Revillagigedo Islands
The Revillagigedo Islands or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem...

 off Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 in the eastern Pacific, as well as many Pacific islands.

As the species common name partly suggests, the island trevally very rarely is found on the continental shelves, instead living around offshore islands formed by volcanic activity
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....

 or isolated slivers of continental material remaining from continental rifting. These islands are often quite large, and have most of the geographical features of the continental environment including beaches, reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

s, lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

s and even estuaries. The island trevally is known from all of these habitats, as well as slightly deeper seaward reefs up to 50 m deep.
In Hawaii, the species is less frequently found inside protected bays, and more often slightly further offshore presumably due to competition with other species.
The island trevally is one of a number of carangid species known to be attracted to man made fish attracting devices, which are installed to aggregate fish for anglers.

Biology and fishery

The island trevally moves both as a solitary individual or in small schools
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...

 through its habitat, with the species often accounting for large proportions of an areas immediate biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 when moving in schools.
The species diet consisting of small fish species and 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, with studies on the species exact diet composition has finding the fish takes different species and different ratios of prey throughout its range. A study conducted in 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...

 found the species consumed 98% fish, with only 1 percent crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

s, while a large study in Hawaii found it took 64.7% crustaceans including crabs, shrimps and stomatopods while taking only 32.3% fish consisting of gobies and benthic fishes of the order scorpaeniformes
Scorpaeniformes
Scorpaeniformes is an order of ray-finned fish, but it has also been called the Scleroparei.They are known as "mail-cheeked" fishes due to their distinguishing characteristic, the suborbital stay: a backwards extension of the third circumorbital bone across the cheek to the preoperculum, to which...

, as well as 2% cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s. In this setting, it appears that the major carangid species in the region alter their diet to reduce interspecific competition
Interspecific competition
Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resource in an ecosystem...

, but change this partitioning elsewhere in their range where they co-occur. Reproduction and growth are poorly studied in the species, with only a general estimate of spawning timing of March in the Solomon Islands.

The island trevally is of moderate importance to fisheries throughout its range, often taken by hook and line, trawls and various types of artisanal gear.
The species is generally only caught as bycatch, with catch numbers often very small in comparison to the target species of the fishery.
Throughout most of its range, catch statistics are not kept. The species is marketed fresh, dry or salted
Salting (food)
Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...

, and is considered a good table fish.

External links

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