The Indian Scad (''Decapterus russelli''), also known as the Northern mackerel scad, round scad, Russell's mackerel scad, slender scad or the three lined grunter, is a species of ray-finned fish of the genus ''

Decapterus ''Decapterus'' is a genus of marine fishes of jack family, Carangidae, commonly known as mackerel scads, round scads, or horse mackerel. They are found throughout the world. Species Currently, 10 or 12 recognized species are found in this genus: ...

'' which is part of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Carangidae The Carangidae are a family of ray-finned fish which includes the jacks, pompanos, jack mackerels, runners, and scads. It is the largest of the six families included within the order Carangiformes. Some authorities classify it as the only family ...

and which occurs in the Indian Ocean. It has colonised the eastern Mediterranean through the Suez Canal. It is an important species in coastal fisheries throughout its range.

Description

''Decapterus russelli'' has an elongate, somewhat slender and slightly compressed body. The eyes are of moderate size and have a well developed adipose eyelid which completely covers eye apart from a vertical slit which has the pupil in its centre. The scales on top of head do not reach a line running through the centre of pupil. The lateral line has a low regular arch towards the head and the curved and straight parts meet below the second

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

between 11th to 13th soft rays; there are 42-62 scales in the curved part of the lateral line and between 0 and 4 scutes, while the straight part has 0 to 4 scales which are followed by 30 to 40 scutes, meaning that the total count of scales and scutes is between 77 and 102m if caudal scutes are excluded). There is a dusky or transparent membrane at the join of the upper jaw, the posterior end of the upper jaw is straight above and a little concave and not horizontal antero-ventrally. Both jaws bear an anterior row of minute teeth which is quite irregular with a single series of posterior teeth. There are 10-14 upper

gill rakers Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the ...

and 30 to 39 lower making a total of 41 to 53 on the first gill arch. The shoulder girdle has 3 small papillae on its margin, the lower one being the larger. There are two widely separate

s, the first is triangular with 8 spines and the second has one spine with 28-33 soft rays. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

has 2 detached spines followed by a single spine and 25-29 soft rays; the terminal dorsal and anal soft rays consist of a widely detached finlet. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

measures 76.5 to 97.0% of the head length. In life it is bluish-green above and silvery below with a small black blotch on the margin of operculum near its upper edge. Caudal fin varies from translucent to dark brown, the second dorsal fin is translucent at its base but light blackish-brown towards the margin; the other fins are mostly translucent, other than the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two e ...

s of adult males which are slightly darker. The spines and rays on the dorsal and anal fin are grey, those on the other finds are white. Its length is up to 45 cm total length, more usually 30 cm and the maximum weight is 110g.

Distribution

''Decapterus russelli'' occurs throughout the Indian Ocean, from the coasts of eastern Africa from the

Gulf of Suez The Gulf of Suez ( ar, خليج السويس, khalīǧ as-suwais; formerly , ', "Sea of Calm") is a gulf at the northern end of the Red Sea, to the west of the Sinai Peninsula. Situated to the east of the Sinai Peninsula is the smaller Gulf o ...

as far south as

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, eastwards into the western Pacific Ocean, from Japan in the north and south to Australia. First recorded in the Mediterranean Sea off Israel in 2005, it is now common in Levantine waters up to Iskenderun (Turkey) and has become an important species in local fisheries.Atlas of Exotic Fishes in the Mediterranean Sea (Decapterus russelli). 2nd Edition. 2021. 366p. CIESM Publishers, Paris, Monaco.https://ciesm.org/atlas/fishes_2nd_edition/Decapterus_russelli.pdf

Biology

Adult ''Decapterus russelli'' are benthic and form large schools in deeper water, although they may occasionally be found inshore in smaller groups where there are sheltered bays. It is the most common species of ''Decapterus'' in coastal waters and on open shallows of the Indian Ocean. Their main prey is smaller planktonic invertebrates, with a study off India finding that the prawn '' Acetes indicus '' being the most numerous prey for both adult and juvenile fish but larger specimens hunt a wide variety of suitably sized fish, including '' Lactarius lactarius'', ''

Leiognathus ''Leiognathus'' is a genus of marine ray-finned fishes, ponyfishes from the family Leiognathidae. They are native to the Indian Ocean and the western Pacific Ocean. They are sometimes known as silverbellies. Species There are currently 7 recogn ...

spp'',

lanternfish Lanternfishes (or myctophids, from the Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented ...

es, eels, ''

Nemipterus ''Nemipterus'' is a genus of fish in the family Nemipteridae. They are native to the Indian and Pacific Oceans, but now also occur in the Mediterranean Sea due to Lessepsian migration. Species There are currently 28 recognized species in this ge ...

spp'', ''

Saurida tumbil The greater lizardfish ''(Saurida tumbil)'' is a species of lizardfish that lives in the Indo-Pacific. They are a minor fishery. Distribution They live in the Indo-West Pacific. More specifically, their geographic range spans from Red Sea and ea ...

'', '' Boleophthalamus sp.'', '' Bregmaceros mcclellandi'', '' Polynemus heptadactylus'', ''

Polynemus indicus ''Polynemus'' is a genus of threadfins (family Polynemidae). They are native to South and Southeast Asia and, depending on the species, occur in freshwater, brackish, and/or marine environments. The family Polynemidae is characterized by the pe ...

'', ''

Cynoglossus ''Cynoglossus'' is a genus of fish in the family Cynoglossidae. Most species are indigenous to the Indo-Pacific region, but there are also a few in warmer parts of the East Atlantic. They are commonly found in shallow waters on a muddy or s ...

spp.'', ''

Trichiurus lepturus The largehead hairtail (''Trichiurus lepturus'') or beltfish is a member of the cutlassfish family, Trichiuridae. This common to abundant species is found in tropical and temperate oceans throughout the world. The taxonomy is not fully resolved, ...

'' and ''

Stolephorus ''Stolephorus'' is a genus of ray-finned fish in the family Engraulidae. Species These are the currently recognized species in this genus: * ''Stolephorus acinaces'' Harutaka Hata & Sébastien Lavoué & Motomura, 2020 * ''Stolephorus advenus'' ...

spp.''. It is host to the

ectoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...

'' Lernanthropus decapteri''. It reaches sexual maturity at around 1 year old and about 12 cm in length

Human usage

Decapterus russelli is fished for wherever it occurs, normally using

seine net Seine fishing (or seine-haul fishing; ) is a method of fishing that employs a surrounding net, called a seine, that hangs vertically in the water with its bottom edge held down by weights and its top edge buoyed by floats. Seine nets can be de ...

s and trawls. In 1999 the total catch was just short of 160,000 tonnes, with the two major fishing nations being

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

and

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

, which landed 82,000 tonnes and 70,160 tonnes respectively. Since the 1950s The weight of Indian scad landed fluctuates and there is no increasing or decreasing trend apparent in the population, however in south-east Asia there has been a marked increase in effort which has not seen an increase n landings suggesting the fishery is over-exploited. It is generally marketed fresh, may be dried or salted, as well as being sold frozen and canned.

Etymology

The specific name honours the Scottish surgeon and

herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning " reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and r ...

Patrick Russell (1726-1805) who had described and illustrated in 1803 but did not give it a specific name. Decapterus russelli India

References

{{Taxonbar, from=Q1042369 Decapterus Marine fauna of East Africa Marine fauna of South Asia Marine fish of Northern Australia Fish described in 1830