''Decapterus russelli'', also known as the Indian scad, northern mackerel scad, round scad, Russell's mackerel scad, slender scad, or three lined grunter, is a species of ray-finned fish in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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

. It naturally occurs in the Indian and the western Pacific Oceans and 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 The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

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 102 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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

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 (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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 110 g.

Distribution

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

Gulf of Suez The Gulf of Suez (; 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 of Aqaba. The gulf was formed within a relative ...

as far south as

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, eastwards into the western Pacific Ocean, from

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

in the north and south to

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. 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 (biology), family Leiognathidae. They are native to the Indian Ocean and the western Pacific Ocean. They are sometimes known as silverbellies. Species There are c ...

'' spp.,

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

es, eels, '' Nemipterus'' 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 ...

'', ''

Boleophthalmus ''Boleophthalmus '' is a genus of mudskippers native to the Indian Ocean and the western Pacific Ocean. Species There are currently six recognized species in this genus: * '' B. birdsongi'' Murdy, 1989 (Birdsong's goggle-eyed goby) * '' B. bod ...

'' sp., '' Bregmaceros mcclellandi'', '' Polynemus heptadactylus'', '' Polynemus indicus'', '' Cynoglossus'' 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. They are found in Atlantic and Indo-pacific Species These are the currently recognized species in this genus: * '' Stolephorus acinaces'' Hata & Lavoué & Motomura, 2020 ...

'' spp. It is host to the

ectoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

'' 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, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

and

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

, 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 in 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 Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honours the

Scottish Scottish usually refers to something of, from, or related to Scotland, including: *Scottish Gaelic, a Celtic Goidelic language of the Indo-European language family native to Scotland *Scottish English *Scottish national identity, the Scottish ide ...

surgeon In medicine, a surgeon is a medical doctor who performs surgery. Even though there are different traditions in different times and places, a modern surgeon is a licensed physician and received the same medical training as physicians before spec ...

and

herpetologist Herpetology (from Ancient Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is a branch of zoology concerned with the study of amphibians (including frogs, salamanders, and caecilians (Gymnophiona)) and reptiles (in ...

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 Fish of the Indian Ocean Fish of the Pacific Ocean Fish of the Mediterranean Sea Marine fish of East Africa Marine fauna of South Asia Fish described in 1830 Taxa named by Eduard Rüppell