Herring scad
Encyclopedia
The herring scad, Alepes vari (also known as the duskyfin crevalle and trevally scad), is a common species
of tropical
marine
fish
in the jack family Carangidae
. The species inhabits the surface waters of coast
al regions throughout the Indo-West Pacific
region, feeding on a variety of crustacean
s and small fishes. It is the largest fish of the scad genus Alepes
, growing to a recorded length of 56 cm. The herring scad is identified among the genus Alepes by its more numerous and smaller scute
s and the number of gill raker
s on the first arch. It is of minor importance to fisheries
throughout its range.
Alepes, a group of fish in the jack family, Carangidae
. The Carangidae are perciform fish in the suborder Percoidei
.
The species was first scientifically described by the French
naturalist
Georges Cuvier
in 1833 from a specimen now lost to science. He named the species Caranx vari, believing the fish was closely affiliated with the large jacks of that genus. The species was later transferred to the scad genus Alepes by Gushiken in 1983, and a specimen from Pondicherry, India was designated to be the lectotype
the following year by Smith-Vaniz. The species was redescribed and renamed twice after Cuvier's description, first by Pieter Bleeker
as Selar macrurus and then by Henry Fowler
as Alepes glabra, both of which are junior synonyms discarded under ICZN
rules. Although commonly called the 'herring scad', the names duskyfin crevalle, trevally scad and, incorrectly, blackfin scad (A. melanoptera
) are applied to the species.
s, the first containing 8 spines while the second has a single spine followed by 24 to 27 soft rays. The anal fin consists of two anteriorally detached small spines followed by a single spine connected to 20 to 23 soft rays. The lateral line
is strongly arched anteriorally with the junction of the curved and straight sections located the origin of second dorsal to the third soft ray. The curved section contains 42 to 50 scales and 0 to 2 scute
s, while the straight section has 0 to 7 scales and 48 to 69 scutes. There is a well-developed adipose eyelid on the posterior half of the eye
. The jaw
s hold a single row of numerous comb like teeth. There are 32 to 38 gill raker
s and a total of 24 vertebrae. The herring scad is by far the largest species in Alepes, growing to 56 cm in total length, although is more commonly encountered at below 30 cm.
The species is an ash blue above, fading to a silvery white below, with a diffuse dusky blotch on margin of operculum
. The fins are dusky with the exception of the spinous dorsal fin which is pale to dark dusky. The amount of dark pigment
in the fins is sexually dimorphic, with males developing darker spinous dorsal fin, lobes of soft dorsal and anal fins, and pelvic fins than females.
oceans. The species has been recorded from the Red Sea
, eastward to Sri Lanka
, India
, Southeast Asia
, China
, Indonesia
, the Philippines
, New Guinea
, and as far north as Taiwan and as far south as northern Australia
. The herring scad is most commonly found in shallow coastal regions where it inhabits the surface layers of the ocean over a variety of substrates.
s including shrimp
s, copepod
s and decapods
as well as other small fishes. It is one of a number of pelagic fish
from the Red Sea found to have high numbers of luminescent bacteria
in its gut, living symbiotically with the fish as part of the gut flora. The species is of little importance to fisheries, taken occasionally on hook and line gear.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of tropical
Tropical fish
Tropical fish include fish found in tropical environments around the world, including both freshwater and salt water species.Tropical fish are popular as aquarium fish, due to their often bright coloration...
marine
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
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 the surface waters of coast
Coast
A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...
al regions throughout the Indo-West Pacific
Indo-West Pacific
The Indo-West Pacific, or IWP, is a zoogeographical region spanning the entire Indian Ocean including the Red Sea and the Pacific Ocean as far as the Caroline Islands but short of the Marshall Islands...
region, feeding on 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 small fishes. It is the largest fish of the scad genus Alepes
Alepes
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...
, growing to a recorded length of 56 cm. The herring scad is identified among the genus Alepes by its more numerous and smaller 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 and the number of 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 on the first arch. It is of minor importance to fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
throughout its range.
Taxonomy and naming
The herring scad is one of five extant species in the scad genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Alepes, a group of fish 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 Carangidae are perciform fish in the suborder Percoidei
Percoidei
Percoidei is one of eighteen suborders of bony fish in the order Perciformes. Many commercially harvested fish species are contained in this suborder, including the snappers, jacks, whitings, groupers, bass, perches and porgies.-Divisions:...
.
The species was first scientifically described by the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
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...
in 1833 from a specimen now lost to science. He named the species Caranx vari, believing the fish was closely affiliated with the large jacks of that genus. The species was later transferred to the scad genus Alepes by Gushiken in 1983, and a specimen from Pondicherry, India was designated to be the lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
the following year by Smith-Vaniz. The species was redescribed and renamed twice after Cuvier's description, first by Pieter Bleeker
Pieter Bleeker
Pieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
as Selar macrurus and then by Henry Fowler
Henry Weed Fowler
Henry Weed Fowler was an American zoologist born in Holmesburg, Pennsylvania.He studied at Stanford University under David Starr Jordan...
as Alepes glabra, both of which are junior synonyms discarded under ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
rules. Although commonly called the 'herring scad', the names duskyfin crevalle, trevally scad and, incorrectly, blackfin scad (A. melanoptera
Blackfin scad
The blackfin scad, Alepes melanoptera, is a species of tropical marine fish of the jack family Carangidae. The species inhabits inshore waters throughout the Indo-Pacific region, although is rare in the western Indian Ocean...
) are applied to the species.
Description
The herring scad has a body profile very similar to other members of the genus Alepes, having a strongly compressed, ovate body. The ventral and dorsal profiles of the fish are almost evenly convex, joined anteriorally by a pointed snout. There are two separate dorsal finDorsal 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 8 spines while the second has a single spine followed by 24 to 27 soft rays. The anal fin consists of two anteriorally detached small spines followed by a single spine connected to 20 to 23 soft rays. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
is strongly arched anteriorally with the junction of the curved and straight sections located the origin of second dorsal to the third soft ray. The curved section contains 42 to 50 scales and 0 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 has 0 to 7 scales and 48 to 69 scutes. There is a well-developed adipose eyelid on the posterior half of the eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
. The jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s hold a single row of numerous comb like teeth. There are 32 to 38 gill raker
Gill raker
Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch and are involved with filter feeding tiny prey. They are not to be confused with the gill filaments that compose the bony part of the gill. Rakers are usually present in two rows, projecting from both the...
s and a total of 24 vertebrae. The herring scad is by far the largest species in Alepes, growing to 56 cm in total length, although is more commonly encountered at below 30 cm.
The species is an ash blue above, fading to a silvery white below, with a diffuse dusky blotch on margin of operculum
Operculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
. The fins are dusky with the exception of the spinous dorsal fin which is pale to dark dusky. The amount of dark pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
in the fins is sexually dimorphic, with males developing darker spinous dorsal fin, lobes of soft dorsal and anal fins, and pelvic fins than females.
Distribution and habitat
The herring scad is distributed throughout tropical to subtropical regions of the Indo-West PacificIndo-West Pacific
The Indo-West Pacific, or IWP, is a zoogeographical region spanning the entire Indian Ocean including the Red Sea and the Pacific Ocean as far as the Caroline Islands but short of the Marshall Islands...
oceans. 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...
, eastward to 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...
, 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...
, Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, 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...
, the 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...
, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, and as far north as Taiwan 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...
. The herring scad is most commonly found in shallow coastal regions where it inhabits the surface layers of the ocean over a variety of substrates.
Biology and fishery
The herring scad is a carnivorous species, known to consume a variety of crustaceanCrustacean
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 including 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, copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s and decapods
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
as well as other small fishes. It is one of a number of pelagic fish
Pelagic fish
Pelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...
from the Red Sea found to have high numbers of luminescent bacteria
Luminescent bacteria
Luminescent bacteria emit light as the result of a chemical reaction during which chemical energy is converted to light energy. Luminescent bacteria exist as symbiotic organisms carried within a larger organism, such as many deep sea organisms, including the Lantern Fish, the Angler fish, certain...
in its gut, living symbiotically with the fish as part of the gut flora. The species is of little importance to fisheries, taken occasionally on hook and line gear.