Razorbelly scad
Encyclopedia
The razorbelly scad, Alepes kleinii (also known as the banded scad, golden scad and goggle-eye scad) is a small species of tropical marine
fish
in the Jack family, Carangidae
. The species inhabits coastal waters in the Indo-Pacific
, from Pakistan
in the west to Japan
and Australia
in the east, often found over reef
s. The razorbelly scad has a complex taxonomic history
, and even recently has had its position in the genus Alepes challenged, but appears to be stable after a molecular phylogeny
study supported the placement in Alepes. It is very similar to other scads in the same genus, but is readily identified by its unique teeth. Razorbelly scad are predatory fish, taking a variety of crustacean
s and shrimp
s, and show a change in feeding intensity over the year. Reproduction and development has been extensively studied in India, where spawning
occurs in a single event from January to September. The species is commonly taken in tropical fisheries where it is marketed fresh or dried.
, which is part of the jack family, Carangidae
. The Carangidae are perciform fishes in the suborder Percoidei
.
Like a number of other members of Alepes, the razorbelly scad suffers from a complicated taxonomic history
, in which the species has been described and named no less than seven times, and has had three of those names reassigned to different genera. The first person to describe and name the species was the German naturalist
Marcus Elieser Bloch
in 1793, assigning the name Scomber kleinii putting the species in a genus of mackerel
. This was later transferred to the jack genus Caranx
and finally to the genus Alepes, which Swainson had created in 1839. This is the currently accepted name, as Bloch was the first to describe the fish, even though he put it in the wrong genus. In a marathon effort of synonymy, Georges Cuvier
described the species under three separate names in 1833, of which two were reclassified into Alepes, forming the commonly used junior synonyms of Alepes para and Alepes kalla. The razorbelly scad was described and named three times after Cuvier's efforts by Bleeker, De Vis and Wakiya. In a 1942 review of Caranx kalla, Nichols tried to separate and rationalise a number of synonyms, even suggesting a subspecies of De Vis' Caranx queenslandiae be created. The type specimen of A. kleinii was collected from the Malabar Coast
off India. Although commonly called razorbelly scad, and recognised as such by fishbase
, the species also is known as banded scad, goggle-eye scad and golden scad.
genus due to it having short conical teeth in comparison to the rest of Alepes comblike teeth. This problem was addressed in a molecular phylogenetic
study of the Carangidae in which A. kleinii and A. djedaba
(Shrimp scad) were included. The results confirmed the placement of A. kleinii in Alepes, with the authors arguing the two species were too closely related to warrant placement in a new genus.
which is further heightened by the different sized lobes of the caudal fin. The head of the fish tapers to a pointed snout
, with the large eye having a well-developed posterior adipose eyelid. The teeth of the fish are a major diagnostic feature of the species, with the upper jaw
having two irregular rows of small conical teeth at the front of the mouth, transitioning to a paving of blunt teeth at the back. The lower jaw is similar, having two rows of short conical teeth in the front of the jaw changing to one row of blunter teeth further back. There are two separate dorsal fin
s, the first containing eight weak spines while the second consists of a single spine followed by 23 to 26 soft rays. The anal fin has two detached spines anterior to the main section, which consists of a single spine followed by 19 to 22 soft rays. The upper caudal fin lobe is larger than the lower lobe, whilst the pelvic fin is quite small in comparison to those of other carangids. The lateral line
is strongly arched anteriorally, with the arched and straight sections of the line intersecting below the fourth to sixth soft dorsal rays. The curved section of the line contains 32 to 46 scales and up to 2 scute
s, while the straight section consists of 35 to 45 scutes and up to 2 scales. The species has 24 vertebrae and a total of 38 to 44 gill raker
s. It is a fairly small fish compared to most carangids, only known to reach 16 cm in length.
Whilst alive, the razorbelly scad is a bluish grey to greenish grey on the upper body, becoming lighter and more silvery ventrally. Dark vertical bands are sometimes present on the body above the lateral line, and a large black spot is present on the upper operculum
and surrounding shoulder region. The fins are pale to hyaline
with the exception of the caudal fin which is yellow to dusky in colour, with the upper lobe generally brighter and having a narrow dusky edge.
-West Pacific region, not as widely distributed as most of the genus Alepes. The species has been recorded from the Red Sea
in the west, but is rarely found west of Pakistan
. It is common along the India
n, Sri Lanka
n and South East Asian coasts, extending throughout Indonesia
, Philippines
, Taiwan
, reaching as far north as Japan
and as far south as northern Australia
. As Caranx kalla, the species was recorded at least once in the Mediterranean Sea
, passing through the Suez Canal
from the Red Sea as part of the Lessepsian migration.
The species inhabits inshore coastal environments, especially reef
habitats.
s and small or larva
l fish
, with smaller amounts of Lucifer
, prawns, amphipods and fish eggs taken.
Reproduction and spawning
in the species has been studied only in Indian waters, where razorbelly scad spawn in a single event from January to September, with peaks in February and in June to August. The eggs are pelagic, spherical and transparent, measuring 0.58 to 0.61 mm in diameter. Newly hatched larvae are 1.13 mm in diameter, and the developmental biology
of the larvae has been well studied. The fecundity
of the species has been shown to be correlated with total length and body weight.
The growth of razorbelly scad was also studied off the Indian coast near Mangalore
. It was found the species grows to 83–84 mm in its first year, 131 mm in the second and 143 mm in the third year of its life. From the data collected, the growth curve predicts a maximum size of 17.1 cm, although it would require a long lifespan. Each sex reaches sexual maturity
at a different size, in males it is 128.5 mm and 126.5 mm in females.
The species is commonly taken as part of a number of fisheries, although catch data is not available. It is taken by methods including hook and line, gill nets as well as other subsistence fishing gear. Razorbelly scad is market
ed fresh and dried salted.
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
in the Jack family, Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
. The species inhabits coastal waters in the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
, from Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
in the west to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and 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 the east, often found over reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s. The razorbelly scad has a complex taxonomic history
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, and even recently has had its position in the genus Alepes challenged, but appears to be stable after a molecular phylogeny
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
study supported the placement in Alepes. It is very similar to other scads in the same genus, but is readily identified by its unique teeth. Razorbelly scad are predatory fish, taking a variety of 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 and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s, and show a change in feeding intensity over the year. Reproduction and development has been extensively studied in India, where 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...
occurs in a single event from January to September. The species is commonly taken in tropical fisheries where it is marketed fresh or dried.
Taxonomy and naming
The razorbelly scad is classified in the scad genus AlepesAlepes
Alepes is a genus containing five extant species of tropical marine fishes in the jack family, Carangidae. They are commonly known as scads, a term applied to many genera of carangid fishes. Their body form, however, differs from these other scads by being much more ovate in shape, more similar to...
, which is part of 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 Carangidae are perciform fishes in the suborder Percoidei
Percoidei
Percoidei is one of eighteen suborders of bony fish in the order Perciformes. Many commercially harvested fish species are contained in this suborder, including the snappers, jacks, whitings, groupers, bass, perches and porgies.-Divisions:...
.
Like a number of other members of Alepes, the razorbelly scad suffers from a complicated taxonomic history
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, in which the species has been described and named no less than seven times, and has had three of those names reassigned to different genera. The first person to describe and name the species was the German naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Marcus Elieser Bloch
Marcus Elieser Bloch
Marcus Elieser Bloch was a German medical doctor and naturalist. He is generally considered one of the most important ichthyologists of the 18th century.- Life :...
in 1793, assigning the name Scomber kleinii putting the species in a genus of mackerel
Mackerel
Mackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...
. This was later transferred to the jack genus Caranx
Caranx
Caranx is a genus of tropical to subtropical marine fish in the jack family Carangidae, commonly known as jacks, trevallies and kingfishes. They are moderate to large sized, deep bodied fishes which are distinguished from other carangid genera by specific gill raker, fin ray and dentition...
and finally to the genus Alepes, which Swainson had created in 1839. This is the currently accepted name, as Bloch was the first to describe the fish, even though he put it in the wrong genus. In a marathon effort of synonymy, 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...
described the species under three separate names in 1833, of which two were reclassified into Alepes, forming the commonly used junior synonyms of Alepes para and Alepes kalla. The razorbelly scad was described and named three times after Cuvier's efforts by Bleeker, De Vis and Wakiya. In a 1942 review of Caranx kalla, Nichols tried to separate and rationalise a number of synonyms, even suggesting a subspecies of De Vis' Caranx queenslandiae be created. The type specimen of A. kleinii was collected from the Malabar Coast
Malabar Coast
The Malabar Coast is a long and narrow coastline on the south-western shore line of the mainland Indian subcontinent. Geographically, it comprises the wettest regions of southern India, as the Western Ghats intercept the moisture-laden monsoon rains, especially on their westward-facing mountain...
off India. Although commonly called razorbelly scad, and recognised as such by fishbase
FishBase
FishBase is a comprehensive database of information about fish species . It is the largest and most extensively accessed online database on adult finfish on the web...
, the species also is known as banded scad, goggle-eye scad and golden scad.
Phylogeny
Although the species, including many of its synonyms, has been placed in the genus Alepes for some time, the nature of its teeth has made this placement controversial. Two authors have argued that the species should be reassigned to a new monotypicMonotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus due to it having short conical teeth in comparison to the rest of Alepes comblike teeth. This problem was addressed in a molecular phylogenetic
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
study of the Carangidae in which A. kleinii and A. djedaba
Shrimp scad
The shrimp scad, Alepes djedaba , is a species of widespread tropical marine fish of the jack family, Carangidae...
(Shrimp scad) were included. The results confirmed the placement of A. kleinii in Alepes, with the authors arguing the two species were too closely related to warrant placement in a new genus.
Description
The razorbelly scad is similar in body shape and profile to the rest of Alepes, possessing a strongly compressed ovate body. The dorsal profile of the body is definitively less convex than the ventral profile, giving the upper and lower parts of the body an asymmetryAsymmetry
Asymmetry is the absence of, or a violation of, symmetry.-In organisms:Due to how cells divide in organisms, asymmetry in organisms is fairly usual in at least one dimension, with biological symmetry also being common in at least one dimension....
which is further heightened by the different sized lobes of the caudal fin. The head of the fish tapers to a pointed snout
Snout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
, with the large eye having a well-developed posterior adipose eyelid. The teeth of the fish are a major diagnostic feature of the species, with 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...
having two irregular rows of small conical teeth at the front of the mouth, transitioning to a paving of blunt teeth at the back. The lower jaw is similar, having two rows of short conical teeth in the front of the jaw changing to one row of blunter teeth further back. There are two separate dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s, the first containing eight weak spines while the second consists of a single spine followed by 23 to 26 soft rays. The anal fin has two detached spines anterior to the main section, which consists of a single spine followed by 19 to 22 soft rays. The upper caudal fin lobe is larger than the lower lobe, whilst the pelvic fin is quite small in comparison to those of other carangids. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
is strongly arched anteriorally, with the arched and straight sections of the line intersecting below the fourth to sixth soft dorsal rays. The curved section of the line contains 32 to 46 scales and up to 2 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, while the straight section consists of 35 to 45 scutes and up to 2 scales. The species has 24 vertebrae and a total of 38 to 44 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. It is a fairly small fish compared to most carangids, only known to reach 16 cm in length.
Whilst alive, the razorbelly scad is a bluish grey to greenish grey on the upper body, becoming lighter and more silvery ventrally. Dark vertical bands are sometimes present on the body above the lateral line, and a large black spot is present on the upper 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....
and surrounding shoulder region. The fins are pale to hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
with the exception of the caudal fin which is yellow to dusky in colour, with the upper lobe generally brighter and having a narrow dusky edge.
Distribution and habitat
The razorbelly scad is broadly distributed over the tropical Eastern IndoIndian 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...
-West Pacific region, not as widely distributed as most of the genus Alepes. The species has been recorded from 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...
in the west, but is rarely found west of Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
. It is common along the 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...
n, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
n and South East Asian coasts, extending throughout 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...
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, reaching as far north as 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 as far south as northern Australia
Northern Australia
The term northern Australia is generally known to include two State and Territories, being Queensland and the Northern Territory . The part of Western Australia north of latitude 26° south—a definition widely used in law and State government policy—is also usually included...
. As Caranx kalla, the species was recorded at least once in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, passing through the Suez Canal
Suez Canal
The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...
from the Red Sea as part of the Lessepsian migration.
The species inhabits inshore coastal environments, especially reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
habitats.
Biology and fishery
The razorbelly scad is a predatory fish, whose feeding activity changes, at least in some regions, over the course of a year. A 1988 study in Indian waters found that the species is an active feeder during February and March, showing only moderate activity for the rest of the year. Their main prey items were small crustaceans, particularly copepodCopepod
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 small or 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...
l 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...
, with smaller amounts of Lucifer
Lucifer (prawn)
Lucifer is a little-known and degenerate genus of prawns, the only genus in the family Luciferidae. Lucifer has a long body, but many fewer appendages than other prawns, with only three pairs of pereiopods remaining, all without claws. It also bears no gills. The females, uniquely among prawns,...
, prawns, amphipods and fish eggs taken.
Reproduction and 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...
in the species has been studied only in Indian waters, where razorbelly scad spawn in a single event from January to September, with peaks in February and in June to August. The eggs are pelagic, spherical and transparent, measuring 0.58 to 0.61 mm in diameter. Newly hatched larvae are 1.13 mm in diameter, and the developmental biology
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
of the larvae has been well studied. The fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
of the species has been shown to be correlated with total length and body weight.
The growth of razorbelly scad was also studied off the Indian coast near Mangalore
Mangalore
Mangalore is the chief port city of the Indian state of Karnataka. It is located about west of the state capital, Bangalore. Mangalore lies between the Arabian Sea and the Western Ghat mountain ranges, and is the administrative headquarters of the Dakshina Kannada district in south western...
. It was found the species grows to 83–84 mm in its first year, 131 mm in the second and 143 mm in the third year of its life. From the data collected, the growth curve predicts a maximum size of 17.1 cm, although it would require a long lifespan. Each sex reaches 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...
at a different size, in males it is 128.5 mm and 126.5 mm in females.
The species is commonly taken as part of a number of fisheries, although catch data is not available. It is taken by methods including hook and line, gill nets as well as other subsistence fishing gear. Razorbelly scad is 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...
ed fresh and dried salted.