155-463: The giant trevally ( Caranx ignobilis ), also known as the lowly trevally , barrier trevally , ronin jack , giant kingfish , or ulua , is a species of large marine fish classified in the jack family , Carangidae . The giant trevally is distributed throughout the tropical waters of the Indo-Pacific region, with a range stretching from South Africa to Hawaii , including Japan in
310-423: A mutation–selection balance . It is predicted that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit, "the quasispecies effect" or the "survival of the flattest". There is no suggestion that a viral quasispecies resembles
465-515: A taxonomic rank of an organism, as well as a unit of biodiversity . Other ways of defining species include their karyotype , DNA sequence, morphology , behaviour, or ecological niche . In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses ) are given
620-542: A two-part name , called a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature , also sometimes in zoological nomenclature ). For example, Boa constrictor is one of the species of the genus Boa , with constrictor being the species' epithet. While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example,
775-400: A "classical" method of determining species, such as with Linnaeus, early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a two-winged mother is not a different species). Species named in this manner are called morphospecies . In the 1970s, Robert R. Sokal , Theodore J. Crovello and Peter Sneath proposed
930-424: A 'smallest clade' idea" (a phylogenetic species concept). Mishler and Wilkins and others concur with this approach, even though this would raise difficulties in biological nomenclature. Wilkins cited the ichthyologist Charles Tate Regan 's early 20th century remark that "a species is whatever a suitably qualified biologist chooses to call a species". Wilkins noted that the philosopher Philip Kitcher called this
1085-465: A bluefin trevally of world-record size, but was later rejected when it was discovered to be a hybrid. Initial evidence of hybridisation was morphological characteristics intermediate to the two species; later genetic tests confirmed it was indeed a hybrid. The two species are known to school together, including at spawning time, which was considered to be the reason for hybridisation. The giant trevally has been used by humans since prehistoric times , with
1240-428: A connected series of neighbouring populations, each of which can sexually interbreed with adjacent related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing
1395-575: 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
1550-432: A different species from its ancestors. Viruses have enormous populations, are doubtfully living since they consist of little more than a string of DNA or RNA in a protein coat, and mutate rapidly. All of these factors make conventional species concepts largely inapplicable. A viral quasispecies is a group of genotypes related by similar mutations, competing within a highly mutagenic environment, and hence governed by
1705-401: A few millimetres in diameter may also be found scattered all over the body, although the coverage of these dots varies between widespread to none at all. All the fins are generally light grey to black, although fish taken from turbid waters often have yellowish fins, with the anal fin being the brightest. The leading edges and tips of the anal and dorsal fins are generally lighter in colour than
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#17327869450941860-508: A genetic boundary suitable for defining a species concept is present. DNA barcoding has been proposed as a way to distinguish species suitable even for non-specialists to use. One of the barcodes is a region of mitochondrial DNA within the gene for cytochrome c oxidase . A database, Barcode of Life Data System , contains DNA barcode sequences from over 190,000 species. However, scientists such as Rob DeSalle have expressed concern that classical taxonomy and DNA barcoding, which they consider
2015-546: A home range, with some evidence of diel and seasonal shifts in habitat use. In the Hawaiian Islands, giant trevally do not normally move between atolls , but have specific core areas where they spend most their time. Within these core areas, habitat shifts during different times of the day have been recorded, with the fish being most active at dawn and dusk, and usually shifting location near sunrise or sunset. Furthermore, large seasonal migrations appear to occur for
2170-477: 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
2325-465: A lineage should be divided into multiple chronospecies , or when populations have diverged to have enough distinct character states to be described as cladistic species. Species and higher taxa were seen from the time of Aristotle until the 18th century as categories that could be arranged in a hierarchy, the great chain of being . In the 19th century, biologists grasped that species could evolve given sufficient time. Charles Darwin 's 1859 book On
2480-554: A major peak during May to August. Lunar cycles are also known to control the spawning events, with large schools forming in certain locations at specific phases of the moon in Hawaii and the Solomon Islands. Locations for spawning include reefs, the reef channels and offshore banks. Sampling of schools prior to spawning suggests the fish segregate into schools of only one sex, although the details are still unclear. Observations in
2635-492: A misnomer, need to be reconciled, as they delimit species differently. Genetic introgression mediated by endosymbionts and other vectors can further make barcodes ineffective in the identification of species. A phylogenetic or cladistic species is "the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts)". The empirical basis – observed character states – provides
2790-449: A particular species, including which genus (and higher taxa) it is placed in, is a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be corroborated or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as
2945-400: A perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that
3100-406: A predator, it eats more than it is worth at market. The giant trevally is of high importance to modern fisheries throughout its range, although quantifying the amounts taken is very difficult due to the lack of fishery statistics kept in most of these countries. Hawaii has the best-kept statistics, where the 1998 catch consisted of 10,194 pounds of giant trevally worth around US$ 12,000. Historically,
3255-480: A recognised gamefish , with the species taken by nets and lines by professionals and by bait and lures by anglers. Catch statistics in the Asian region show hauls of 4,000–10,000 tonnes , while around 10,000 lb of the species are taken in Hawaii each year. The species is considered poor to excellent table fare by different authors, although ciguatera poisoning is common from eating the fish. Dwindling numbers around
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#17327869450943410-657: A sandy bottom, where eggs and sperm were released. The fish then diverged and swam away. Each individual appears to spawn more than once in each period, with only part of the gonads ripe in spawners. Fecundity is not known, although females are known to release several thousand eggs on capture during the spawning process. Eggs are described as pelagic and transparent in nature. The giant trevally's early larval stages and their behaviour have been extensively described, with all fins having formed by at least 8 mm in length, with larvae and subjuveniles being silver with six dark vertical bars. Laboratory populations of fish show
3565-400: A short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics . However, abbreviations such as "sp." should not be italicised. When a species' identity is not clear,
3720-475: A significant variability in the length at a certain age, with the average range being around 6.5 mm. Growth rates in larvae between 8.0 and 16.5 mm are on average 0.36 mm per day. The speed at which larvae swim increases with age from 12 cm/s at 8 mm in length to 40 cm/s at 16.5 mm, with size rather than age a better predictor of this parameter. Size is also a better predictor of endurance in larvae than age. These observations suggest
3875-445: A silvery colour with occasional dark spots, but males may be black once they mature. It is the largest fish in the genus Caranx , growing to a maximum known size of 170 cm (67 in) and a weight of 80 kg (176 lb). The giant trevally inhabits a wide range of marine environments, from estuaries , shallow bays, and lagoons as a juvenile to deeper reefs , offshore atolls , and large embayments as an adult. Juveniles of
4030-429: A small patch of scales in front of the pelvic fins. The upper jaw contains a series of strong outer canines with an inner band of smaller teeth, while the lower jaw contains a single row of conical teeth. The species has 20 to 24 gill rakers in total and 24 vertebrae are present. The eye is covered by a moderately well-developed adipose eyelid , and the posterior extremity of the jaw is vertically under or just past
4185-404: A specialist may use "cf." before the epithet to indicate that confirmation is required. The abbreviations "nr." (near) or "aff." (affine) may be used when the identity is unclear but when the species appears to be similar to the species mentioned after. With the rise of online databases, codes have been devised to provide identifiers for species that are already defined, including: The naming of
4340-523: A species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. It has been argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection. Mayr's use of the adjective "potentially" has been a point of debate; some interpretations exclude unusual or artificial matings that occur only in captivity, or that involve animals capable of mating but that do not normally do so in
4495-400: A species as determined by a taxonomist. A typological species is a group of organisms in which individuals conform to certain fixed properties (a type), so that even pre-literate people often recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens (such as longer or shorter tails) would differentiate the species. This method was used as
4650-491: A species. All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT. There is strong evidence of HGT between very dissimilar groups of prokaryotes , and at least occasionally between dissimilar groups of eukaryotes , including some crustaceans and echinoderms . The evolutionary biologist James Mallet concludes that there
4805-685: A species. Generally the term includes the unknown element of a distinct act of creation. Many authors have argued that a simple textbook definition, following Mayr's concept, works well for most multi-celled organisms , but breaks down in several situations: Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorised as two types: (i) one morphology, multiple lineages (e.g. morphological convergence , cryptic species ) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity , multiple life-cycle stages). In addition, horizontal gene transfer (HGT) makes it difficult to define
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4960-528: A taxonomic decision at the discretion of cognizant specialists, is not governed by the Codes of Zoological or Botanical Nomenclature, in contrast to the PhyloCode , and contrary to what is done in several other fields, in which the definitions of technical terms, like geochronological units and geopolitical entities, are explicitly delimited. The nomenclatural codes that guide the naming of species, including
5115-517: A traditional biological species. The International Committee on Taxonomy of Viruses has since 1962 developed a universal taxonomic scheme for viruses; this has stabilised viral taxonomy. Most modern textbooks make use of Ernst Mayr 's 1942 definition, known as the Biological Species Concept as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept. This defines
5270-447: A variation on the morphological species concept, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms. It differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species
5425-428: A varied array of invertebrates . These include crustaceans such as shrimps , decapods , copepods and stomatopods , cephalopods , 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
5580-515: A variety of reasons. Viruses are a special case, driven by a balance of mutation and selection , and can be treated as quasispecies . Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics . Early taxonomists such as Linnaeus had no option but to describe what they saw: this was later formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts,
5735-408: A wide array of lures . The species is commonly taken on bibbed plugs, minnows, spoons, jigs and poppers, stickbaits, soft plastic lures and saltwater flies . In recent years, the development of both jigging and surface-popping techniques has seen the giant trevally become an extremely popular candidate for catch and release fishing , with many charter operators based around this concept. The species
5890-438: Is "an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies". This differs from the biological species concept in embodying persistence over time. Wiley and Mayden stated that they see the evolutionary species concept as "identical" to Willi Hennig 's species-as-lineages concept, and asserted that
6045-399: Is 'bigeye trevally', 'bigeye kingfish', 'bigeye crevalle jack' or bigeye jack', with other names used including 'great trevally', 'six-banded trevally' and 'dusky jack'. 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 kg in weight. It is similar to most other jacks in having a compressed, oblong body, with
6200-441: 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 dusk 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
6355-400: Is a group of sexually reproducing organisms that recognise one another as potential mates. Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridise successfully, they are still distinct cohesion species if
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6510-458: Is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognise as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters. A genetic species as defined by Robert Baker and Robert Bradley is a set of genetically isolated interbreeding populations. This
6665-573: 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 sharks and larger species of carangid to sea lions and various birds. The bigeye trevally reaches sexual maturity at
6820-442: Is also popular with spearfishermen throughout its range. The species' edibility has been rated from poor to excellent by different authors, although numerous cases of ciguatera poisoning have been reported from the species. Detailed tests on a large (1 m) specimen taken from Palmyra Island showed the toxicity of the fish's flesh, liver and washed intestinal tract produced no or weakly positive symptoms to laboratory mice, but
6975-557: 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 reefs 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
7130-414: Is called speciation . Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species . Speciation depends on a measure of reproductive isolation , a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate. Reproductive isolation
7285-653: Is commercially caught by a number of methods, including hook and line, handlines, gill nets and other types of artisanal traps. The species has also successfully been bred for aquaculture purposes in Taiwan. It is sold at market fresh, frozen, salted , and smoked , and as fishmeal and oil . The giant trevally is considered one of the top gamefish of the Indo-Pacific region, having outstanding strength, speed and endurance once hooked. It can be taken by many methods, including baits of cut or live fish and squid, as well as
7440-515: Is commonly found in large slow moving schools during the day, becoming active at night when it feeds, taking a variety of fish, crustaceans , cephalopods 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
7595-403: Is described formally, in a publication that assigns it a unique scientific name. The description typically provides means for identifying the new species, which may not be based solely on morphology (see cryptic species ), differentiating it from other previously described and related or confusable species and provides a validly published name (in botany) or an available name (in zoology) when
7750-450: Is estimated at between 3.82 and 20.87 g/day, with larger fish growing at a more rapid rate. Length at the age of one year is 18 cm, at two years is 35 cm and by three years, the fish is around 50 to 60 cm. The use of von Bertalanffy growth curves fitted to observed otolith data show an individual of around 1 m in length is about eight years old, while a 1.7 m fish would be around 24 years old. The maximum theoretical length of
7905-671: Is further weakened by the existence of microspecies , groups of organisms, including many plants, with very little genetic variability, usually forming species aggregates . For example, the dandelion Taraxacum officinale and the blackberry Rubus fruticosus are aggregates with many microspecies—perhaps 400 in the case of the blackberry and over 200 in the dandelion, complicated by hybridisation , apomixis and polyploidy , making gene flow between populations difficult to determine, and their taxonomy debatable. Species complexes occur in insects such as Heliconius butterflies, vertebrates such as Hypsiboas treefrogs, and fungi such as
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#17327869450948060-726: Is hard or even impossible to test. Later biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, and the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: (1) agamospecies for asexual organisms (2) biospecies for reproductively isolated sexual organisms (3) ecospecies based on ecological niches (4) evolutionary species based on lineage (5) genetic species based on gene pool (6) morphospecies based on form or phenotype and (7) taxonomic species,
8215-419: 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 bays and lagoons 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
8370-443: Is more likely to be ciguatoxic, so if the fish is kept, it must be disposed of or sent to a taxidermist if it is a trophy fish. A catch and release approach has also been adopted by operators outside Hawaii, with Australian operators who target the species by popping and jigging rarely keeping any fish. Careful fish handling techniques have also been implemented by anglers so as not to damage the fish; such techniques include supporting
8525-420: Is mostly demersal in nature. The species is most common in shallow coastal waters in a number of environments, including coral and rocky reefs and shorefaces, lagoons , embayments, tidal flats and channels. They commonly move between reef patches, often over large expanses of deeper sand and mud bottoms between the reefs. Older individuals tend to move to deeper seaward reefs, bomboras and drop-offs away from
8680-492: Is much rarer in estuaries. The species has a wide salinity tolerance, as evident from the ranges from which juvenile and subadult fish in South African estuaries have been recorded; 0.5 to 38 parts per thousand (ppt), with other studies also showing tolerance levels of less than 1 ppt. In these estuaries, the giant trevally is known from both highly turbid , dirty water to clean, high visibility waters, but in most cases,
8835-403: Is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods. The botanist Brent Mishler argued that the species concept
8990-478: Is not valid, notably because gene flux decreases gradually rather than in discrete steps, which hampers objective delimitation of species. Indeed, complex and unstable patterns of gene flux have been observed in cichlid teleosts of the East African Great Lakes . Wilkins argued that "if we were being true to evolution and the consequent phylogenetic approach to taxa, we should replace it with
9145-404: 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. The bigeye trevally is classified within
9300-420: 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. Filipinos 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
9455-586: Is similar to Mayr's Biological Species Concept, but stresses genetic rather than reproductive isolation. In the 21st century, a genetic species could be established by comparing DNA sequences. Earlier, other methods were available, such as comparing karyotypes (sets of chromosomes ) and allozymes ( enzyme variants). An evolutionarily significant unit (ESU) or "wildlife species" is a population of organisms considered distinct for purposes of conservation. In palaeontology , with only comparative anatomy (morphology) and histology from fossils as evidence,
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#17327869450949610-441: Is sometimes an important source of genetic variation. Viruses can transfer genes between species. Bacteria can exchange plasmids with bacteria of other species, including some apparently distantly related ones in different phylogenetic domains , making analysis of their relationships difficult, and weakening the concept of a bacterial species. Bigeye trevally The bigeye trevally ( Caranx sexfasciatus ), also known as
9765-403: Is the largest member of the genus Caranx , and the fifth-largest member of the family Carangidae (exceeded by the yellowtail amberjack , greater amberjack , leerfish , and rainbow runner ), with a recorded maximum length of 170 cm (67 in) and a weight of 80 kg (180 lb). Specimens of 50 kg and above are not uncommon in sportfishing. The Hallaniyat Islands in southern Oman are
9920-421: Is thought juvenile seals being followed in this way may be outcompeted by the larger fish. A similar strategy has been employed by fish in the presence of large reef sharks , as they use the larger animal as a tool to ambush prey. The opportunistic nature of giant trevally has also been made evident by studies on the mortality rate of undersized or egg-bearing lobsters released from traps at the water's surface of
10075-594: Is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model . A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form (a chronospecies ), without increasing the number of resultant species. Horizontal gene transfer between organisms of different species, either through hybridisation , antigenic shift , or reassortment ,
10230-530: The ICZN for animals and the ICN for plants, do not make rules for defining the boundaries of the species. Research can change the boundaries, also known as circumscription, based on new evidence. Species may then need to be distinguished by the boundary definitions used, and in such cases the names may be qualified with sensu stricto ("in the narrow sense") to denote usage in the exact meaning given by an author such as
10385-612: The Philippines , Fiji , and the Solomon Islands . Along continental Asia, the species has been recorded from Malaysia to Vietnam, but not China. Despite this, its offshore range does extend north to Hong Kong , Taiwan, and southern Japan. In the south, the species reaches as far south as New South Wales in Australia and even to the northern tip of New Zealand in the southern Pacific. Its distribution continues throughout
10540-463: The Red Sea off both Yemen and Saudi Arabia, with one of these designated to be the holotype . He named the species Scomber ignobilis , with the specific epithet Latin for "unknown", "obscure" or "ignoble". It was assigned to the mackerel genus Scomber , where many carangids were placed before they were classified as a separate family. This later revision in classification saw the species moved to
10695-480: 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 Oceans, 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
10850-461: 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 scutes . 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
11005-479: 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
11160-399: The fly agaric . Natural hybridisation presents a challenge to the concept of a reproductively isolated species, as fertile hybrids permit gene flow between two populations. For example, the carrion crow Corvus corone and the hooded crow Corvus cornix appear and are classified as separate species, yet they can hybridise where their geographical ranges overlap. A ring species is
11315-507: The jaguar ( Panthera onca ) of Latin America or the leopard ( Panthera pardus ) of Africa and Asia. In contrast, the scientific names of species are chosen to be unique and universal (except for some inter-code homonyms ); they are in two parts used together : the genus as in Puma , and the specific epithet as in concolor . A species is given a taxonomic name when a type specimen
11470-425: 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 Niño or La Niña climate events, with the abundance significantly dropping during El Niño events. The bigeye trevally
11625-511: The northwestern Hawaiian Islands showed the giant trevally was of high ecological importance, constituting 71% of the apex predator biomass , and was the dominant apex predator. This number is considerably less in heavily fished Hawaiian waters. The species is prey to sharks, especially when small. Conversely, adult giant trevallies, either singles or pairs, have been recorded attacking sharks (like blacktip reef shark ) by ramming them repeatedly with their head. The shark, sometimes even larger than
11780-438: The ventral profile, particularly anteriorly . The dorsal fin is in two parts, the first consisting of eight spines and the second of one spine followed by 18 to 21 soft rays . The anal fin consists of two anteriorly detached spines followed by one spine and 15 to 17 soft rays. The pelvic fins contain 1 spine and 19 to 21 soft rays. The caudal fin is strongly forked, and the pectoral fins are falcate, being longer than
11935-406: The "cynical species concept", and arguing that far from being cynical, it usefully leads to an empirical taxonomy for any given group, based on taxonomists' experience. Other biologists have gone further and argued that we should abandon species entirely, and refer to the "Least Inclusive Taxonomic Units" (LITUs), a view that would be coherent with current evolutionary theory. The species concept
12090-710: The French naturalists 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
12245-510: The Hawaiian Islands suggest the population is slightly skewed toward females, with the male:female ratio being 1:1.39. Spawning occurs during the warmer months in most locations, although the exact dates differ by location. In southern Africa, this occurs between July and March, with a peak between November and March; in the Philippines between December and January, with a lesser peak during June; and in Hawaii between April and November, with
12400-564: The Hawaiian Islands. The fish are efficient predators of these crustaceans, with individuals often seizing a lobster before it could sink to the seafloor after being released, or attacking before the lobster moves into a defensive position. Some bolder, large individuals are even known to eat the lobster head first when it is in a defensive stance. The giant trevally reaches sexual maturity at 54 to 61 cm in length and three to four years of age, although many authors narrow this down to 60 cm and three years of age. Sex ratio estimates from
12555-592: The Indian Ocean, the species' westernmost range is the coast of continental Africa, being distributed from the southern tip of South Africa north along the east African coastline to the Red Sea and Persian Gulf . Its range extends eastwards along the Asian coastline, including Pakistan, India and into Southeast Asia, the Indonesian Archipelago and northern Australia. The southernmost record from
12710-626: The Origin of Species explained how species could arise by natural selection . That understanding was greatly extended in the 20th century through genetics and population ecology . Genetic variability arises from mutations and recombination , while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures . Genes can sometimes be exchanged between species by horizontal gene transfer ; new species can arise rapidly through hybridisation and polyploidy ; and species may become extinct for
12865-793: 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 seamounts . The species
13020-405: The abbreviation "sp." in the singular or "spp." (standing for species pluralis , Latin for "multiple species") in the plural in place of the specific name or epithet (e.g. Canis sp.). This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology . Authors may also use "spp." as
13175-570: The amount of hybridisation is insufficient to completely mix their respective gene pools . A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology , genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that members of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA–DNA hybridisation to decide if they belong to
13330-446: 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
13485-475: 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
13640-474: The biological species concept, "the several versions" of the phylogenetic species concept, and the idea that species are of the same kind as higher taxa are not suitable for biodiversity studies (with the intention of estimating the number of species accurately). They further suggested that the concept works for both asexual and sexually-reproducing species. A version of the concept is Kevin de Queiroz 's "General Lineage Concept of Species". An ecological species
13795-505: The biological species concept, a cladistic species does not rely on reproductive isolation – its criteria are independent of processes that are integral in other concepts. Therefore, it applies to asexual lineages. However, it does not always provide clear cut and intuitively satisfying boundaries between taxa, and may require multiple sources of evidence, such as more than one polymorphic locus, to give plausible results. An evolutionary species, suggested by George Gaylord Simpson in 1951,
13950-428: The boundaries between closely related species become unclear with hybridisation , in a species complex of hundreds of similar microspecies , and in a ring species . Also, among organisms that reproduce only asexually , the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be
14105-433: The concept of a chronospecies can be applied. During anagenesis (evolution, not necessarily involving branching), some palaeontologists seek to identify a sequence of species, each one derived from the phyletically extinct one before through continuous, slow and more or less uniform change. In such a time sequence, some palaeontologists assess how much change is required for a morphologically distinct form to be considered
14260-431: The contrary. This was due to the highly size-selective nature of the fishery, which theoretically should prevent a decrease in numbers. Despite this, populations have decreased, and in light of their continued falling abundance in Hawaii, several recommendations, including banning the commercial take of the species, increasing minimum lengths and decreasing bag limits for anglers, as well as reassessment of protected areas for
14415-504: 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 buoys , indicating
14570-472: The digested contents of the intestine were lethal. The authors argued, based on this test, the flesh of giant trevally was safe to consume. However, analysis of case studies in which ciguatera poisoning was reported after eating the fish suggested an accumulative effect occurs with repeated consumption; and tests like the one outlined above are not reliable, as the toxin appears to be distributed haphazardly throughout each fish. Since 1990, giant trevally taken from
14725-435: The evidence to support hypotheses about evolutionarily divergent lineages that have maintained their hereditary integrity through time and space. Molecular markers may be used to determine diagnostic genetic differences in the nuclear or mitochondrial DNA of various species. For example, in a study done on fungi , studying the nucleotide characters using cladistic species produced the most accurate results in recognising
14880-441: The fish are on the bite, especially after dusk. The species is also occasionally taken from beaches , 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
15035-489: The fish was seen as a god , and treated as gamefish which commoners could not hunt. There are many mentions of ulua in Hawaiian proverbs , all generally relating to the strength and warrior-like qualities of the fish. The Hawaiians considered the fish to be of excellent quality, with white, firm flesh. Despite this, intrusions of giant trevally into modern-day fishponds used by Hawaiians for rearing fish are unwelcome; being
15190-411: The fish's weight, using barbless single, rather than treble, hooks and restricting the time the fish spends out the water to a minimum. Species A species ( pl. : species) is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring , typically by sexual reproduction . It is the basic unit of classification and
15345-582: The formerly saltwater Taal Lake , and are referred to as maliputo to distinguish them from the marine variant (locally named talakitok ). Along with Taal Volcano and Taal Lake, the maliputo is prominently featured on the reverse side of the newly redesigned Philippine 50 peso bill . The giant trevally is a solitary fish once it reaches sexual maturity , only schooling for the purposes of reproduction and more rarely for feeding. Juveniles and subadults commonly school, both in marine and estuarine environments. Observations from South African estuaries indicate
15500-444: The genus Caranx , 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 , which in turn is part of the order Carangiformes . 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
15655-650: The genus Caranx , where it has remained. Even after its initial description, the giant trevally (and the bigeye trevally ) were often confused with the Atlantic crevalle jack , Caranx hippos , due to their superficial similarity, which led to some authors claiming the crevalle jack had a circumtropical distribution. After Forsskål's initial description and naming, the species was independently renamed three times as Caranx lessonii , Caranx ekala and Carangus hippoides , all of which are now considered invalid junior synonyms . The latter of these names once again highlighted
15810-459: The giant trevally is a silvery-grey fish, with the head and upper body slightly darker in both sexes. Fish greater than 50 cm show sexual dimorphism in their colouration, with males having dusky to jet-black bodies, while females are a much lighter coloured silvery-grey. Individuals with darker dorsal colouration often also display striking silvery striations and markings on the upper part of their bodies, particularly their backs. Black dots of
15965-433: The giant trevally is to 'escort' monk seals , a behavior which has been observed near the Hawaiian Islands. The trevally swim close by the seal, and when the seal stops to forage, the trevally positions its mouth inches away from the seal. If a prey item is disturbed, the trevally will attempt to steal the prey from the seal, which routinely does occur. The seal does not appear to gain any benefit from this relationship, and it
16120-480: The giant trevally's feeding strategies have found hunting in schools increases their capture efficiency, but is not necessary for an individual's survival. When a school is formed during feeding, one individual will take a leading position, with others trailing behind it. Several individuals will attack the prey school, striking and stunning the prey, with the leading individual generally being more successful. Some individuals act individually and opportunistically within
16275-542: 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
16430-400: The length of the head. The lateral line has a pronounced and moderately long anterior arch, with the curved section intersecting the straight section below the lobe of the second dorsal fin. The curved section of the lateral line contains 58-64 scales , while the straight section contains none to four scales and 26 to 38 very strong scutes . The chest is devoid of scales with the exception of
16585-502: The main Hawaiian Islands have also led to several proposals to reduce the catch of fish in this region. The giant trevally is classified within the genus Caranx , 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 , which in turn is part of the order Carangiformes . The giant trevally was first scientifically described by Swedish naturalist Peter Forsskål in 1775 based on specimens taken from
16740-435: The main Hawaiian islands have been blocked from sale by auction internationally due to concerns over liability from ciguatera poisoning. A decline in giant trevally numbers around inhabited regions has been well documented in Hawaii, with both catch data as presented above and ecological studies showing this decrease in numbers. A biomass study in the Hawaiian Islands indicates the main Hawaiian Islands are heavily depleted in
16895-545: 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 larvae of bigeye trevally have been extensively described, with defining features being
17050-514: The main part of the fins. There is no black spot on the operculum . Traces of broad cross-bands on the fish's sides are occasionally seen after death. The fishes have been known to prey and eat on the dead fish. The giant trevally is widely distributed throughout the tropical and subtropical waters of the Bay of Bengal and Indian and Pacific Oceans, ranging along the coasts of three continents and many hundreds of smaller islands and archipelagos . In
17205-452: The most common prey taken at 89% of stomach content by volume, with fish, mostly of the family Blennidae, making up only 7% of the stomach contents. Estuarine fish in both Hawaii and Australia have mostly fish-based diets, with crustaceans such as prawns and amphipods also of importance, and they are known to take more novel prey, such as spiders and insects, in these habitats. Juvenile turtles and dolphins were reported being found within
17360-441: 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
17515-419: The most prolific places for these large fish, with fish of 100 lb being caught almost daily. Unfortunately in recent times, the fishery has dwindled with commercial pressure and fish that size are becoming ever rarer throughout the islands. The giant trevally is similar in shape to a number of other large jacks and trevallies, having an ovate, moderately compressed body with the dorsal profile more convex than
17670-412: The natural habitat found spawning occurred during the day immediately after and just before the change of tide when there were no currents . Giant trevally gathered in schools of over 100 individuals, although ripe individuals occurred slightly deeper; around 2–3 m above the seabed in groups of three or four, with one silver female being chased by several black males. Eventually, a pair would sink down to
17825-458: The north and Australia in the south. Two were documented in the eastern tropical Pacific in the 2010s (one captured off Panama and another sighted at the Galápagos ), but whether the species will become established there remains to be seen. The giant trevally is distinguished by its steep head profile, strong tail scutes , and a variety of other more detailed anatomical features. It is normally
17980-483: The numerous fungi species of all the concepts studied. Versions of the phylogenetic species concept that emphasise monophyly or diagnosability may lead to splitting of existing species, for example in Bovidae , by recognising old subspecies as species, despite the fact that there are no reproductive barriers, and populations may intergrade morphologically. Others have called this approach taxonomic inflation , diluting
18135-477: 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 IGFA maintains a full set of line class and tippet records for the bigeye jack. The all tackle world record stands at 14.30 kg (31 lb 8 oz) caught off Poivre Island in the Seychelles . The bigeye trevally's edibility
18290-418: The oldest known records of the capture of this species by Hawaiians, whose culture held the fish in high regard. The ulua , as the fish is known to Hawaiians, was likened to a fine man and strong warrior , which was the cause of a ban on women eating the species in antiquity. The species was often used in Hawaiian religious rites , and took the place of a human sacrifice when none was available. Culturally,
18445-593: The paper is accepted for publication. The type material is usually held in a permanent repository, often the research collection of a major museum or university, that allows independent verification and the means to compare specimens. Describers of new species are asked to choose names that, in the words of the International Code of Zoological Nomenclature , are "appropriate, compact, euphonious, memorable, and do not cause offence". Books and articles sometimes intentionally do not identify species fully, using
18600-674: The person who named the species, while the antonym sensu lato ("in the broad sense") denotes a wider usage, for instance including other subspecies. Other abbreviations such as "auct." ("author"), and qualifiers such as "non" ("not") may be used to further clarify the sense in which the specified authors delineated or described the species. Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct. The evolutionary process by which biological populations of sexually-reproducing organisms evolve to become distinct or reproductively isolated as species
18755-441: The posterior margin of the pupil. The eye of the giant trevally has a horizontal streak in which ganglion and photoreceptor cell densities are markedly greater than the rest of the eye. This is believed to allow the fish to gain a panoramic view of its surroundings, removing the need to constantly move the eye, which in turn will allow easier of detection of prey or predators in that field of view. At sizes less than 50 cm,
18910-470: The predominant species around these structures in Taiwan. Juvenile to subadult giant trevally are known to enter and inhabit estuaries, the upper reaches of rivers and coastal lakes in several locations, including South Africa, Solomon Islands, Philippines, India, Taiwan, Thailand, northern Australia, and Hawaii. In some of these locations, such as Australia, it is a common and relatively abundant inhabitant, while in others, including South Africa and Hawaii, it
19065-440: The presence of squid and the schooling carangid Decapterus macarellus indicates exploitation of more open-water habitats, as well. Off Africa, the diet is similar, consisting mostly of fish including eels , with minor squid, octopus, mantis shrimp , lobsters and other crustaceans. Younger fish inside Kaneohe Bay , Hawaii showed the only instance where crustaceans were preferred over fish; stomatopods , shrimp and crabs were
19220-480: The protection of fringing reefs, often to depths greater than 80 m. Large individuals, however, often return to these shallower waters as they patrol their ranges, often to hunt or reproduce. In Hawaii, the juvenile to subadult giant trevally is the most common large carangid in the protected inshore waters, with all other species apparently preferring the outer, less protected reefs. It is also easily attracted to artificial reefs , where studies have found it to be one of
19375-490: The purpose of aggregating for spawning, with this also known from the Solomon Islands. Despite not moving between atolls, they do make periodic atoll-wide journeys of up to 29 km. Long-term studies show juveniles can move up to 70 km away from their protected habitats to outer reefs and atolls. The giant trevally is one of the most important apex predators in its habitats, both as adults on reefs and as juveniles in estuaries. Observations in relatively untouched waters of
19530-487: The result of misclassification leading to questions on whether there really are any ring species. The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus , or the cat family, Felidae . Another problem with common names is that they often vary from place to place, so that puma, cougar, catamount, panther, painter and mountain lion all mean Puma concolor in various parts of America, while "panther" may also mean
19685-586: The ring. Ring species thus present a difficulty for any species concept that relies on reproductive isolation. However, ring species are at best rare. Proposed examples include the herring gull – lesser black-backed gull complex around the North pole, the Ensatina eschscholtzii group of 19 populations of salamanders in America, and the greenish warbler in Asia, but many so-called ring species have turned out to be
19840-508: The same species. This concept was narrowed in 2006 to a similarity of 98.7%. The average nucleotide identity (ANI) method quantifies genetic distance between entire genomes , using regions of about 10,000 base pairs . With enough data from genomes of one genus, algorithms can be used to categorize species, as for Pseudomonas avellanae in 2013, and for all sequenced bacteria and archaea since 2020. Observed ANI values among sequences appear to have an "ANI gap" at 85–95%, suggesting that
19995-529: The same species. When two species names are discovered to apply to the same species, the older species name is given priority and usually retained, and the newer name considered as a junior synonym, a process called synonymy . Dividing a taxon into multiple, often new, taxa is called splitting . Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognising differences or commonalities between organisms. The circumscription of taxa, considered
20150-406: The school if one of the prey fish becomes isolated, with the main advantage of schooling appearing to be the ability to further break up and isolate prey schools. The only time hunting in schools is a disadvantage is when only isolated prey are present, such as close to a reef; here, an individual hunter has a greater probability of capturing it than if a group is present. Another hunting strategy of
20305-456: The schools of smaller juveniles tend not to intermingle with schools of other species, but larger subadults are known to form mixed-species schools with the brassy trevally . Research has been conducted on the movements of larger fish around their habitats, as well as the movement between habitats as the species grows, to understand how marine reserves impact on the species. Adult giant trevally are known to range back and forth up to 9 km along
20460-624: The second dorsal fin has a distinctive white tip. The bigeye trevally also has a small dark opercular spot on the upper margin. The bigeye trevally is widely distributed throughout the tropical and subtropical waters of both the Indian and Pacific Oceans. 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
20615-727: The similarity with the crevalle jack, with the epithet hippoides essentially meaning "like Carangus hippos ", which was the crevalle jack's Latin name at that time. Despite the resemblance with the crevalle jack, the two species have never been phylogenetically compared, either morphologically or genetically, to determine their relationship. C. ignobilis is most commonly referred to as the giant trevally (or giant kingfish) due to its large maximum size, with this often abbreviated to simply GT by many anglers. Other names occasionally used include lowly trevally, barrier trevally, yellowfin jack (not to be confused with Hemicaranx leucurus ), Forsskål's Indo-Pacific jack fish and Goyan fish. In Hawaii ,
20770-625: The species are known to live in waters of very low salinity such as coastal lakes and upper reaches of rivers, and tend to prefer turbid waters. The giant trevally is an apex predator in most of its habitats, and is known to hunt individually and in schools. The species predominantly takes various fish as prey , although crustaceans , cephalopods , and molluscs make up a considerable part of their diets in some regions. Their novel hunting strategies include shadowing monk seals to pick off escaping prey, using sharks to ambush prey, and leaping to catch birds. The giant trevally reproduces in
20925-470: The species becomes an effective swimmer (is able to swim against a current) around 7–14 mm. No obvious relationships with age and either swimming depth or trajectory have been found. Larvae appear to also opportunistically feed on small zooplankton while swimming. The larvae actively avoid other large fish, and jellyfish are occasionally used as temporary cover. Larvae have no association with reefs, and appear to prefer to live pelagically . Daily growth
21080-506: The species concept and making taxonomy unstable. Yet others defend this approach, considering "taxonomic inflation" pejorative and labelling the opposing view as "taxonomic conservatism"; claiming it is politically expedient to split species and recognise smaller populations at the species level, because this means they can more easily be included as endangered in the IUCN red list and can attract conservation legislation and funding. Unlike
21235-546: The species has been taken in far greater numbers, and has been an important food, market and game fish since the early 1900s. However, their exploitation has seen the landings of the species decrease by over 84% since the turn of the century, declining from 725,000 lb to 10,000 lb in recent catches. FAO statistics of the Asian region record catches between 4,000 and 10,000 tonnes between 1997 and 2007, although this excludes most fisheries which are not monitored or do not discriminate between trevally species. The giant trevally
21390-440: The species is almost exclusively referred to as ulua , often in conjunction with the prefixes black, white, or giant. Due to its wide distribution, many other names for the species in different languages are also used. In the Philippines, the species is referred to as talakitok . Some success has been achieved in raising giant trevally commercially in small fish farms there, typically to an age of seven months. The giant trevally
21545-403: 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
21700-424: The species predicted by the growth curves is 1.84 m, but the largest reported individual was 1.7 m long. As previously mentioned, as the giant trevally grows, it shifts from turbid inshore waters or estuaries to reefs and lagoons in bays, moving finally to outer reefs and atolls. A hybrid of C. ignobilis and C. melampygus ( bluefin trevally ) has been recorded from Hawaii. The specimen was initially thought to be
21855-425: The species prefers the turbid waters. Younger fish apparently actively seek out these turbid waters, and when no estuaries are present, they live in the turbid inshore waters of bays and beaches . These young fish eventually move to inshore reefs as they mature, before again moving to deeper outer reefs. In the Philippines, a population of giant trevally inhabit (and were once common in) the landlocked fresh waters of
22010-454: 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
22165-403: The species, have been proposed by officials. The species (nor any other carangid) has not been assessed by the IUCN . Some recreational fishing groups are also promoting a catch and release practice for the giant trevally, with this becoming an increasingly popular option for charter boat operators, who have also begun to tag giant trevally for scientific purposes. At large sizes, the species
22320-402: The species, which in untouched ecosystems comprises 71% of the apex predator biomass. In contrast, it comprises less than 0.03% of the apex biomass in exploited habitats, with only a single fish observed during the course of this research study. Prior to this, a 1993 report suggested the population around the main Hawaiian islands were not stressed, though several biological indicators suggested to
22475-581: The stomach contents of larger giant trevally. Studies of different size classes of fish have found their diets change with age in some locations, with the changes relating to an increased volume of fish taken. Giant trevally also feed on fledgling sooty terns on Farquhar Atoll snatching them from the water surface and even jumping acrobatically to catch them in the air as seen on the BBC documentary Blue Planet II , episode 1. So far this behaviour has not been observed elsewhere. Studies in controlled environments on
22630-427: The trevally, may die from the attack. The reason for this behavior is unclear, but the giant trevally does not attempt to eat the dead shark. Rarely, they have been recorded behaving in the same way towards humans: A spearfisher in Hawaii broke three ribs when rammed by a giant trevally. Large giant trevallies have been recorded as a host of the sharksucker , Echeneis naucrates , a fish which is normally seen attached to
22785-459: The two species vastly different lifestyles and spawning characteristics. As all fish species, the bigeye trevally harbours parasites . These include Monogeneans , Digeneans , Acanthocephalans , Nematodes , Copepodes , and Isopodes ; of these, the protomicrocotylid monogenean Neomicrocotyle pacifica is the more abundant. The bigeye trevally is of varying importance to both commercial and recreational fisheries throughout its range, with
22940-573: The undersides of sharks. The giant trevally is a powerful predatory fish , from the estuaries it inhabits as a juvenile to the outer reefs and atolls it patrols as an adult. Hunting appears to occur at different times of the day in different areas of its range; off South Africa it is most active during the day, especially at dawn and dusk, while off Zanzibar and Hong Kong, it is nocturnal in its habits. The species' diets have been determined in several countries and habitats; their diets generally vary slightly by locations and age. In all but one study (which
23095-443: The upper jaw , with a row of widely spaced conical teeth on the lower jaw. The bigeye trevally has 21 to 25 gill rakers 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,
23250-410: The warmer months, with peaks differing by region. Spawning occurs at specific stages of the lunar cycle , when large schools congregate to spawn over reefs and bays, with reproductive behaviour observed in the wild. The fish grow relatively fast, reaching sexual maturity at a length around 60 cm at three years of age. The giant trevally is both an important species to commercial fisheries and
23405-437: 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 anglers , 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
23560-531: The west coast of Australia comes from Rottnest Island , not far offshore from Perth . Elsewhere in the Indian Ocean, the species has been recorded from hundreds of small island groups, including the Maldives , Seychelles , Madagascar and the Cocos (Keeling) Islands . The giant trevally is abundant in the central Indo-Pacific region, found throughout all the archipelagos and offshore islands including Indonesia,
23715-475: The western Pacific, including Tonga , Western Samoa , and Polynesia , with its easternmost limits known to be the Pitcairn and Hawaiian Islands. The giant trevally inhabits a very wide range of offshore and inshore marine environments, with the species also known to tolerate the low salinity waters of estuaries and rivers. It is a semipelagic fish known to spend time throughout the water column, but
23870-540: The wild. It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of Species : I was much struck how entirely vague and arbitrary is the distinction between species and varieties. He went on to write: No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of
24025-498: Was of juveniles), the giant trevally dominantly takes other fishes, with various crustaceans , cephalopods and occasionally molluscs making the remainder of the diet. In Hawaii, the species has a predominantly fish-based diet consisting of Scaridae and Labridae , with crustaceans, including lobsters , and cephalopods (squid and octopus) making up the remaining portion. The large number of reef fishes suggests it spends much of its time foraging over shallow-water reef habitats, but
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