Bigeye trevally
Encyclopedia
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 distributed throughout the tropical waters of the Indian
and Pacific Ocean
s, ranging from South Africa
in the west to California
and Ecuador
in the east, including Australia
to the south and Japan
in the north. The bigeye trevally is best distinguished by its colouration, having a dark second dorsal fin
with a white tip on the lobe, and also possessing a small dark spot on the operculum
. Other more detailed anatomical features also set the species apart from other members of Caranx
. The species is known to grow to a length of 120 cm and 18 kg
.
It is predominantly an inshore fish, inhabiting reef
s down to depths of around 100 m in both coastal zones and offshore
islands, often venturing into estuaries and sandy bays as juveniles. The bigeye trevally is commonly found in large slow moving schools during the day, becoming active at night when it feeds, taking a variety of fish, crustacean
s, cephalopod
s and other invertebrates. The fish is known to move from a more crustacean dominated diet as a juvenile to a nearly completely fish dominated diet as an adult. Sexual maturity
is reached at 42 cm, with spawning
occurring in large aggregations occurring at different periods throughout its range, generally between July and March. The bigeye trevally is of moderate importance to fisheries throughout its range, and being of high importance to some artisanal fisheries. It is taken by gill net, purse seine, hook and line and other artisanal fishing methods. It is rated as a fair to good table fish. The species is also considered a good gamefish, taken by lure, bait and spear throughout its range.
, 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
, a group of percoid
fishes in the order Perciformes
.
Prior to its description in 1825, the species was often confused with the similar-looking Atlantic species Caranx hippos, and its synonym Caranx carangus. The species was first properly scientifically described by the French naturalist
s Jean René Constant Quoy
and Joseph Paul Gaimard
in 1825 from a specimen collected off Waigeo
, Indonesia
which was designated to be the holotype
. They named the species Caranx sexfasciatus which the species is still currently accepted as, with the specific epithet meaning 'six banded' in relation to its juvenile colouration. Following this, the species was independently redescribed and named around fifteen times, and incorrectly broken into two subspecies
. In his massive ichthyological volume entitled Histoire Naturelle des Poissons
, Georges Cuvier
managed to assign no less than four junior synonyms to the species, while the most recent renaming was by Yojiro Wakiya in 1924, who applied the name Caranx oshimai. The two subspecies proposed were Caranx sexfaciatus elacate and Caranx sexfaciatus marginatus, both based on prior descriptions by Jordan
and Evermann
, and Gill respectively. All names except Caranx sexfasciatus are considered junior synonyms under ICZN
rules and discarded.
The common name
preferred by most authorities is 'bigeye trevally', 'bigeye kingfish', 'bigeye crevalle jack' or bigeye jack', with other names used including 'great trevally', 'six-banded trevally' and 'dusky jack'.
in weight. It is similar to most other jacks in having a compressed, oblong
body, with the dorsal profile slightly more convex than the ventral profile, particularly anteriorly. The snout is slightly pointed, and is greater in length than the eye diameter. The dorsal fin
is in two distinct sections; the first consisting of 8 spine and the second of 1 spine and 19 to 22 soft rays. The anal fin consists of 2 anteriorly detached spines followed by 1 spine and 14 to 17 soft rays. The pelvic fins consists of 1 spine and 17 to 18 soft rays, while the caudal fin is strongly forked and the pectoral fin falcate. The species lateral line
is moderately arched anteriorly, with 49 to 50 scales in this section, while the straight section contains 0 to 3 scales
and 27 to 36 strong scute
s. The breast is completely covered in scales. The species has well-developed adipose eyelids, while its dentition consists of an outer row of widely spaced canine
teeth and an inner band of villiform teeth in the upper jaw
, with a row of widely spaced conical teeth on the lower jaw. The bigeye trevally has 21 to 25 gill raker
s and 25 vertebrae.
The bigeye trevally shows a change in colour as it ages, changing both overall colour and body patterns. Juveniles are a silvery yellow to silvery brown in colour, and possess five to six dark vertical
bands on their sides, from which the specific epithet sexfasciatus arose. As they mature, the bands fade and become indistinct and the overall colour shifts to a silvery blue above and whitish below. In adults, the bars are completely absent and the dorsal colour is a silvery olive to blue green, fading to silvery white below. In juveniles, the fins are pale grey to yellow with darker edges, becoming darker overall in adulthood, with the anal and caudal fins yellow to black and the second dorsal fin olive to black. The tip of the second dorsal fin has a distinctive white tip. The bigeye trevally also has a small dark opercular
spot on the upper margin.
and Pacific Ocean
s. In the Indian Ocean, it ranges from South Africa
and Madagascar
in the west, along the east African coastline up to both the Red Sea
and Persian Gulf
. Its range extends east along India
, South East Asia, Indonesia
and many offshore Indian Ocean islands. The range extends north to Japan
and south to Australia
in this central Indo-pacific region. In the Pacific Ocean, the bigeye trevally inhabits most of the tropical island groups including Hawaii
,
with its range extending east to the western American coastline. In this eastern region of its distribution it has been recorded from the American state of California
in the north, including the Gulf of California
, and south to Ecuador
and the Galapagos Islands
.
The bigeye trevally predominantly live in inshore coastal waters, although does occur in pelagic settings far offshore
, and around remote islands and seamount
s. The species is known to reach depths of around 100 m. It is mostly found over coral
and rocky reef
complexes as adults, however often moves into more inshore areas in sandy bay
s and lagoon
s in small numbers. Those that live offshore often live on deeper seamounts or reefs around offshore islands. The species moves with the tide in some regions, entering shallow lagoonal areas as the tide rises, and moving back to the deeper reefs as it retreats. Juveniles inhabit more inshore, shallower waters around the coast, often venturing into lagoons, tidal flats, mangrove
zones and even estuaries. Juvenile bigeye trevally have been reported in rivers from several locations, and are known to penetrate well into the upper reaches of rivers.
As the fish grows, it moves back to deeper waters over reefs. The species has been reported in pelagic open ocean settings, milling around stationary buoy
s, indicating the species may follow floating debris far out to sea.
The bigeye trevally is a schooling
species, known to form aggregations consisting of more than 1500 fish. The species is often seen in these large schools either stationary or slowly moving around the reef complexes they inhabit during the day. At night, these schools dissolve, and the species become active, taking most of its prey during the nocturnal period. This contrasts to most jacks, which are generally diurnal hunters, although the species has been documented hunting in shallower waters during the day, especially as juveniles. The abundance of the species on the west coast of America has been linked to the occurrence of El Nino or La Nina
climate events, with the abundance significantly dropping during El Nino events.
and through the night. The large stationary aggregations break off as the fish move off to hunt in small groups or individually. The species predominantly takes small fish as prey, however supplements its diet with a varied array of invertebrate
s. These include crustacean
s such as shrimp
s, decapods
, copepod
s and stomatopods, cephalopod
s, gastropods, jellyfish
, sponges and even species of open ocean sea-skater insects. Bigeye trevally were found to be the primary fish predators of these sea-skates, and took far more of these than any other species of carangid. Evidence from South African estuaries indicates there is a shift in the species diet as it grows. Young fish below 200 mm in length take mostly the juveniles of other fish species but still have a significant intake of penaeid shrimps, while fish larger than this take small fish nearly exclusively. The larger fish on reefs tend to move between these reefs regularly, which is thought to be due to prey availability. Bigeye trevally are also an important prey for larger species, ranging from shark
s and larger species of carangid to sea lions and various birds.
at a length of around 42 cm, with both males and females reaching maturity at a similar length and age. Spawning
is known to occur between July and September in the east Pacific and in November to March in South Africa, indicating variation across the species range. There is also evidence that spawning may occur during new moon periods. Fish aggregate in large schools prior to spawning, with pairs breaking off the main aggregation to commence spawning. The pair increase their swimming speed to leave the school, with the fish underneath instantly changing colour to a dark black, with this individual also known to chase off any other individuals that approach the pair. The trevally then press their ventral surfaces together to spawn, often swimming almost horizontally
, before returning to the school and changing back to their normal silvery colour.
The larva
e of bigeye trevally have been extensively described, with defining features being a conspicuously pigmented supraoccipital crest, relatively deep body and an anal fin ray count of 15 to 17, the lowest of any east Pacific carangid. There has been little research into the later stages of growth and their rates. Juveniles are known to inhabit either inshore habitats such as estuaries, with an influx of these small fish after spawning in South Africa, while in other cases juveniles have been found living pelagically around floating objects.
There has been one documented hybrid involving the bigeye trevally, a cross between C. sexfasciatus and C. melampygus (bluefin trevally
), taken from the waters of Kane'ohe Bay, Hawaii.
The specimen was initially thought to be a bigeye trevally, however a lack of the black opercular spot, light coloured scutes and a smaller than normal eye led to the specimen being examined in more detail. DNA
analysis confirmed a hybrid between C. sexfasciatus and C. melampygus, which has been difficult to explain due to the two species vastly different lifestyles and spawning characteristics.
The bigeye trevally is of varying importance to both commercial and recreational fisheries throughout its range, with the large school sizes allowing for large catches in some regions. In many regions the species is lumped with other jacks in fishery statistics
, and therefore worldwide catch is nearly impossible to estimate. Known recent annual catches include those of Saudi Arabia
(615–638 t
), Mexico
(900 t), and Hawaii
(297 lb
). The species is especially important in fisheries based around coral reefs, with one such fishery in Papua New Guinea
showing bigeye trevally are the most frequently taken carangid, and one of the top five most important species overall. It is also of high importance in small artisanal and subsistence fisheries, for which statistics are not kept. Bigeye trevally are taken by a number of methods including hook and line, gill nets, purse seines and various other netting methods. Due to their nocturnal hunting nature, a popular way to catch large numbers involves illuminating the water surface at night, and using hook and line to catch the fish attracted by the light. The species is sold fresh, dried and salted
at market
.
The bigeye trevally is also popular with angler
s, with the species rated as an excellent gamefish in larger sizes. The species is commonly taken by boat fishermen over reef complexes, however schools often hang around jetties
and wharves
, allowing for frantic fishing when the fish are on the bite, especially after dusk. The species is also occasionally taken from beach
es, but rarely in large quantities. Common techniques for catching the fish include bait fishing, which can involve both live or dead bit including fish, squid
or various crustaceans, or lure fishing. Bigeye trevally are known to accept many lure types including bibbed lures, surface poppers and metal slugs jigged in rapid retrieve from the ocean floor. Soft plastic lures are known to take the species, as are saltwater fly
patterns. In larger sizes, gear must be robust and well maintained to land the fish.
The bigeye trevally's edibility
is said to range from fair to very good, with frying, steaming, grilling and even use in soup
popular in some South East Asian countries. Filipino
s are said to consider the fish of high quality, especially fish taken from the volcanic Lake Taal, which are said to have a delicate flavour due to the lake's sulphur content. Apart from fishing, the species is popular with scuba divers which often photograph the huge schools that mill around reefs during the day. Bigeye trevally have also been held in large saltwater aquaria, however require large tank volumes to survive.
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 widespread large 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...
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 bigeye trevally is distributed throughout the tropical 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 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 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 California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
in the east, including Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
to the south 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. The bigeye trevally is best distinguished by its colouration, having a dark 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...
with a white tip on the lobe, and also possessing a small dark spot 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....
. Other more detailed anatomical features also set the species apart from other members of 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...
. The species is known to grow to a length of 120 cm and 18 kg
Kilogram
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...
.
It is predominantly an inshore fish, inhabiting reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s down to depths of around 100 m in both coastal zones and 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, often venturing into estuaries and sandy bays as juveniles. The bigeye trevally is commonly found in large slow moving schools during the day, becoming active at night when it feeds, taking a variety of fish, 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, 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 and other invertebrates. The fish is known to move from a more crustacean dominated diet as a juvenile to a nearly completely fish dominated diet as an adult. Sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is reached at 42 cm, with spawning
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
occurring in large aggregations occurring at different periods throughout its range, generally between July and March. The bigeye trevally is of moderate importance to fisheries throughout its range, and being of high importance to some artisanal fisheries. It is taken by gill net, purse seine, hook and line and other artisanal fishing methods. It is rated as a fair to good table fish. The species is also considered a good gamefish, taken by lure, bait and spear throughout its range.
Taxonomy and naming
The bigeye trevally is classified within the genus CaranxCaranx
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...
, 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
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...
, a group of percoid
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:...
fishes in 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...
.
Prior to its description in 1825, the species was often confused with the similar-looking Atlantic species Caranx hippos, and its synonym Caranx carangus. The species was first properly scientifically described by the French naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
s Jean René Constant Quoy
Jean René Constant Quoy
Jean René Constant Quoy was a French zoologist.Along with Joseph Paul Gaimard he served as naturalist aboard La Coquille under Louis Isidore Duperrey during its circumnavigation of the globe , and the Astrolabe under the command of Jules Dumont d'Urville...
and Joseph Paul Gaimard
Joseph Paul Gaimard
Joseph Paul Gaimard was a French naval surgeon and naturalist.Along with Jean René Constant Quoy he served as naturalist on the ships L'Uranie under Louis de Freycinet 1817-1820, and L'Astrolabe under Jules Dumont d'Urville 1826-1829...
in 1825 from a specimen collected off Waigeo
Waigeo
Waigeo is an island in West Papua province of eastern Indonesia. The island is also known as Amberi, or Waigiu. It is the largest of the four main islands in the Raja Ampat Islands archipelago, between Halmahera and about 65 km to the northwest coast of New Guinea...
, 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...
. They named the species Caranx sexfasciatus which the species is still currently accepted as, with the specific epithet meaning 'six banded' in relation to its juvenile colouration. Following this, the species was independently redescribed and named around fifteen times, and incorrectly broken into two 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...
. In his massive ichthyological volume entitled Histoire Naturelle des Poissons
Histoire Naturelle des Poissons
Histoire Naturelle des Poissons was a 22-volume study of Ichthyology written by Georges Cuvier and his student Achille Valenciennes in the 1830s....
, Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
managed to assign no less than four junior synonyms to the species, while the most recent renaming was by Yojiro Wakiya in 1924, who applied the name Caranx oshimai. The two subspecies proposed were Caranx sexfaciatus elacate and Caranx sexfaciatus marginatus, both based on prior descriptions by 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 Evermann
Barton Warren Evermann
Barton Warren Evermann was an American ichthyologist. He was born in Monroe County, Iowa, and graduated from Indiana University in 1886. For 10 years, he served as teacher and superintendent of schools in Indiana and California. He was professor of biology at the Indiana State University in...
, and Gill respectively. All names except Caranx sexfasciatus are considered junior synonyms under 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...
rules and discarded.
The 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...
preferred by most authorities is 'bigeye trevally', 'bigeye kingfish', 'bigeye crevalle jack' or bigeye jack', with other names used including 'great trevally', 'six-banded trevally' and 'dusky jack'.
Description
The bigeye trevally is one of the larger members of Caranx, growing to a maximum recorded size of 120 cm in length and 18.0 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...
in weight. It is similar to most other jacks in having 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...
body, with the dorsal profile slightly more convex than the ventral profile, particularly anteriorly. The snout is slightly pointed, and is greater in length than the eye diameter. 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 distinct sections; the first consisting of 8 spine and the second of 1 spine and 19 to 22 soft rays. The anal fin consists of 2 anteriorly detached spines followed by 1 spine and 14 to 17 soft rays. The pelvic fins consists of 1 spine and 17 to 18 soft rays, while the caudal fin is strongly forked and the pectoral fin falcate. The species 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...
is moderately arched anteriorly, with 49 to 50 scales in this section, while the straight section contains 0 to 3 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...
and 27 to 36 strong 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 completely covered in scales. The species has well-developed adipose eyelids, while its dentition consists of an outer row of widely spaced canine
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
teeth and an inner band of villiform teeth in the upper 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...
, with a row of widely spaced conical teeth on the lower jaw. The bigeye trevally has 21 to 25 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 25 vertebrae.
The bigeye trevally shows a change in colour as it ages, changing both overall colour and body patterns. Juveniles are a silvery yellow to silvery brown in colour, and possess five to six dark vertical
Vertical direction
In astronomy, geography, geometry and related sciences and contexts, a direction passing by a given point is said to be vertical if it is locally aligned with the gradient of the gravity field, i.e., with the direction of the gravitational force at that point...
bands on their sides, from which the specific epithet sexfasciatus arose. As they mature, the bands fade and become indistinct and the overall colour shifts to a silvery blue above and whitish below. In adults, the bars are completely absent and the dorsal colour is a silvery olive to blue green, fading to silvery white below. In juveniles, the fins are pale grey to yellow with darker edges, becoming darker overall in adulthood, with the anal and caudal fins yellow to black and the second dorsal fin olive to black. The tip of the second dorsal fin has a distinctive white tip. The bigeye trevally also has a small dark opercular
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....
spot on the upper margin.
Distribution and habitat
The bigeye trevally is widely distributed throughout the tropical and subtropical waters of both 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 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 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...
and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
in the west, along the east African coastline up to both the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and Persian Gulf
Persian Gulf
The Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
. Its range extends east along 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...
, 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 many offshore Indian Ocean islands. The range extends north 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 south to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
in this central Indo-pacific region. In the Pacific Ocean, the bigeye trevally inhabits most of the tropical island groups including 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...
,
with its range extending east to the western American coastline. In this eastern region of its distribution it has been recorded from the American state of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in the north, including the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
, and south to Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
and the Galapagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
.
The bigeye trevally predominantly live in inshore coastal waters, although does occur in pelagic settings far 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,...
, and around remote islands and seamount
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
s. The species is known to reach depths of around 100 m. It is mostly found over coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
and rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
complexes as adults, however often moves into more inshore areas in sandy 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 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 in small numbers. Those that live offshore often live on deeper seamounts or reefs around offshore islands. The species moves with the tide in some regions, entering shallow lagoonal areas as the tide rises, and moving back to the deeper reefs as it retreats. Juveniles inhabit more inshore, shallower waters around the coast, often venturing into lagoons, tidal flats, mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
zones and even estuaries. Juvenile bigeye trevally have been reported in rivers from several locations, and are known to penetrate well into the upper reaches of rivers.
As the fish grows, it moves back to deeper waters over reefs. The species has been reported in pelagic open ocean settings, milling around stationary buoy
Buoy
A buoy is a floating device that can have many different purposes. It can be anchored or allowed to drift. The word, of Old French or Middle Dutch origin, is now most commonly in UK English, although some orthoepists have traditionally prescribed the pronunciation...
s, indicating the species may follow floating debris far out to sea.
Biology
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...
species, known to form aggregations consisting of more than 1500 fish. The species is often seen in these large schools either stationary or slowly moving around the reef complexes they inhabit during the day. At night, these schools dissolve, and the species become active, taking most of its prey during the nocturnal period. This contrasts to most jacks, which are generally diurnal hunters, although the species has been documented hunting in shallower waters during the day, especially as juveniles. The abundance of the species on the west coast of America has been linked to the occurrence of El Nino or La Nina
La Niña
La Niña is a coupled ocean-atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño-Southern Oscillation climate pattern. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5 °C...
climate events, with the abundance significantly dropping during El Nino events.
Diet and feeding
The bigeye trevally is a fast-swimming predatory species that has had several studies determine its diet in various places throughout its distribution. As mentioned above, the species is mostly inactive during the day, and feeds at duskDusk
Dusk is the beginning of darkness in the evening, and occurs after twilight, when the sky generally remains bright and blue. Civil dusk is when the earth has rotated enough that the center of the sun is at 6° below the local horizon...
and through the night. The large stationary aggregations break off as the fish move off to hunt in small groups or individually. The species predominantly takes small fish as prey, however supplements its diet with a varied array of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. These include 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 such as 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, decapods
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
, copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s and stomatopods, 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, gastropods, jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
, sponges and even species of open ocean sea-skater insects. Bigeye trevally were found to be the primary fish predators of these sea-skates, and took far more of these than any other species of carangid. Evidence from South African estuaries indicates there is a shift in the species diet as it grows. Young fish below 200 mm in length take mostly the juveniles of other fish species but still have a significant intake of penaeid shrimps, while fish larger than this take small fish nearly exclusively. The larger fish on reefs tend to move between these reefs regularly, which is thought to be due to prey availability. Bigeye trevally are also an important prey for larger species, ranging from shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s and larger species of carangid to sea lions and various birds.
Reproduction and growth
The bigeye trevally reaches sexual maturitySexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at a length of around 42 cm, with both males and females reaching maturity at a similar length and age. Spawning
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
is known to occur between July and September in the east Pacific and in November to March in South Africa, indicating variation across the species range. There is also evidence that spawning may occur during new moon periods. Fish aggregate in large schools prior to spawning, with pairs breaking off the main aggregation to commence spawning. The pair increase their swimming speed to leave the school, with the fish underneath instantly changing colour to a dark black, with this individual also known to chase off any other individuals that approach the pair. The trevally then press their ventral surfaces together to spawn, often swimming almost horizontally
Horizontal plane
In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...
, before returning to the school and changing back to their normal silvery colour.
The larva
Larva
A larva 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...
e of bigeye trevally have been extensively described, with defining features being a conspicuously pigmented supraoccipital crest, relatively deep body and an anal fin ray count of 15 to 17, the lowest of any east Pacific carangid. There has been little research into the later stages of growth and their rates. Juveniles are known to inhabit either inshore habitats such as estuaries, with an influx of these small fish after spawning in South Africa, while in other cases juveniles have been found living pelagically around floating objects.
There has been one documented hybrid involving the bigeye trevally, a cross between C. sexfasciatus and C. melampygus (bluefin trevally
Bluefin trevally
The bluefin trevally, Caranx melampygus , is a species of large, widely distributed marine fish classified in the jack family, Carangidae...
), taken from the waters of Kane'ohe Bay, Hawaii.
The specimen was initially thought to be a bigeye trevally, however a lack of the black opercular spot, light coloured scutes and a smaller than normal eye led to the specimen being examined in more detail. DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
analysis confirmed a hybrid between C. sexfasciatus and C. melampygus, which has been difficult to explain due to the two species vastly different lifestyles and spawning characteristics.
Relationship to humans
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
, and therefore worldwide catch is nearly impossible to estimate. Known recent annual catches include those of Saudi Arabia
Saudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
(615–638 t
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
), 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...
(900 t), and 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...
(297 lb
LB
-Codes:*.lb, the Internet country code top-level domain for Lebanon*Labrador's former postal abbreviation*Lloyd Aéreo Boliviano airline's IATA code*Luxembourgish language's ISO 639 alpha-2 code*Lebanon's ISO 3166-1 alpha-2 country code...
). The species is especially important in fisheries based around coral reefs, with one such fishery in Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
showing bigeye trevally are the most frequently taken carangid, and one of the top five most important species overall. It is also of high importance in small artisanal and subsistence fisheries, for which statistics are not kept. Bigeye trevally are taken by a number of methods including hook and line, gill nets, purse seines and various other netting methods. Due to their nocturnal hunting nature, a popular way to catch large numbers involves illuminating the water surface at night, and using hook and line to catch the fish attracted by the light. The species is sold fresh, dried and 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
Market
A market is one of many varieties of systems, institutions, procedures, social relations and infrastructures whereby parties engage in exchange. While parties may exchange goods and services by barter, most markets rely on sellers offering their goods or services in exchange for money from buyers...
.
The bigeye trevally is also popular with angler
Angling
Angling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
s, with the species rated as an excellent gamefish in larger sizes. The species is commonly taken by boat fishermen over reef complexes, however schools often hang around jetties
Jetty
A jetty is any of a variety of structures used in river, dock, and maritime works that are generally carried out in pairs from river banks, or in continuation of river channels at their outlets into deep water; or out into docks, and outside their entrances; or for forming basins along the...
and wharves
Wharf
A wharf or quay is a structure on the shore of a harbor where ships may dock to load and unload cargo or passengers.Such a structure includes one or more berths , and may also include piers, warehouses, or other facilities necessary for handling the ships.A wharf commonly comprises a fixed...
, allowing for frantic fishing when the fish are on the bite, especially after dusk. The species is also occasionally taken from beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es, but rarely in large quantities. Common techniques for catching the fish include bait fishing, which can involve both live or dead bit including fish, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
or various crustaceans, or lure fishing. Bigeye trevally are known to accept many lure types including bibbed lures, surface poppers and metal slugs jigged in rapid retrieve from the ocean floor. Soft plastic lures are known to take the species, as are saltwater fly
Fly fishing
Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...
patterns. In larger sizes, gear must be robust and well maintained to land the fish.
The bigeye trevally's edibility
Fish (food)
Fish is a food consumed by many species, including humans. The word "fish" refers to both the animal and to the food prepared from it. Fish has been an important source of protein for humans throughout recorded history.-Terminology:...
is said to range from fair to very good, with frying, steaming, grilling and even use in soup
Soup
Soup is a generally warm food that is made by combining ingredients such as meat and vegetables with stock, juice, water, or another liquid. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth.Traditionally,...
popular in some South East Asian countries. Filipino
Filipino people
The Filipino people or Filipinos are an Austronesian ethnic group native to the islands of the Philippines. There are about 92 million Filipinos in the Philippines, and about 11 million living outside the Philippines ....
s are said to consider the fish of high quality, especially fish taken from the volcanic Lake Taal, which are said to have a delicate flavour due to the lake's sulphur content. Apart from fishing, the species is popular with scuba divers which often photograph the huge schools that mill around reefs during the day. Bigeye trevally have also been held in large saltwater aquaria, however require large tank volumes to survive.