Smallmouth scad

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Smallmouth scad
Smallmouth scad.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Carangiformes
Family: Carangidae
Genus: Alepes
Species:
A. apercna
Binomial name
Alepes apercna
Alepes apercna distribution.PNG
Range of the smallmouth scad

The smallmouth scad (Alepes apercna) (also known as the banded scad and roundfin trevally), is a species of tropical marine fish in the jack family Carangidae. The species is endemic to northern Australia, inhabiting primarily inshore waters. It is similar to other scads in the genus Alepes , and is distinguished by a well-developed posterior adipose eyelid, as well as fin membrane spotting and gill raker counts. It is not a large species, with the maximum length reported to be 29.5 cm. It feeds primarily on a variety of small invertebrates, and is of very minor economic importance.

Contents

Taxonomy and naming

The smallmouth scad is one of five members in the scad genus Alepes, which is one of 33 genera of the jack family, Carangidae. The Carangidae are part of the order Carangiformes. [2]

The smallmouth scad has a slightly confusing taxonomic history, with confusion over the classification, the author, and confusion with other species clouding the species past. The first specimen known to science was taken in 1984, and deposited in the Queensland Museum along with photographs of a juvenile as paratypes with no holotype designated. Grant described the species for the first time in 1987 in "Fishes of Australia", crediting the species to Smith-Vaniz, who presumably collected the specimen and wrote a brief description. However, Grant's description of the species is the first publication of the species, making him the correct author under the ICZN rules. [3] Confusion over this species and Alepes kleinii led Sainsbury to refer to the species as Alepes sp., with the placement in the genus considered somewhat dubious. The type locality is listed only as Australia. [4] The common name of the species is related to the small mouth size of the species, with the names banded scad and roundfin trevally used incorrectly, and this is partially due to confusion with A. kleinii, the true banded scad. [4]

Description

The smallmouth scad has an elongate oval to oblong shaped body which is strongly compressed. The snout is blunt, and both the ventral and dorsal profiles are equally convex. The dorsal and anal fins both have a low profile, and are not falcate, while the pectorals are falcate and extend beyond the junction of the curved and straight lateral line. [5] The curved section of the lateral line is strongly arched, rising from the origin at the operculum and terminating at the junction with the straight section. A posterior adipose eyelid is well developed and reaches almost to the center of the eye, and the jaws are filled with fine teeth. The first dorsal fin has 8 spines, and the second dorsal has one spine and 24-26 soft rays. The anal fin has two separate spines posterior to the main anal fin which consists of one spine and 20 to 22 soft rays. There are 51-70 moderately protrusive scutes. [3] It is similar to Atule mate , but lacks the adipose eyelid on both posterior and anterior sides of the orbit. It is also very similar to Alepes melanoptera and is distinguished from it by having dusky to hyaline dorsal intermembranes, compared to A. melanoptera's spotted membranes. Alepes vari is more similar still, and can be clearly distinguished by gill raker counts, having 27-30 compared to A. vari's 37. [5] The largest specimen known was taken by the CSIRO and measured 29.5 cm. [6]

The colour of the body is a blue to green blue above and silver below, with young specimens having dark vertical cross bars. The operculum has a diffuse dark blotch. The spinous and soft dorsal fins, anal fins and caudal fin are a dusky yellow green. The anterior of the soft dorsal and anal fins have white tips and the pelvic fin is a white to grey colour, while the pectoral is hyaline. [5]

Distribution and habitat

The smallmouth scad is known only from Australian waters, inhabiting the tropical north from Exmouth Gulf in Western Australia, north to the Northern Territory and east to Wide Bay in Queensland. [4] There has been a single report of an individual as far down as Botany Bay in New South Wales. [7] The species may also occur in the Gulf of Papua but has not yet reported. It is an abundant fish on the continental shelf in waters from 10 to 150 m in depth, rarely leading a pelagic lifestyle. [3]

Biology and fishery

Smallmouth scad are omnivorous, but take a high proportion of small invertebrates, primarily benthic crustaceans and molluscs. [3] It also frequently ingests algae, a feature which is rare in the Carangidae. [5] Nothing of the reproductive cycle is known. It is of little importance to fisheries, usually caught on hook and line tackle by commercial and recreational fishermen. [3]

Related Research Articles

Shrimp scad Species of fish

The shrimp scad, is a species of widespread tropical marine fish of the jack family, Carangidae. The shrimp scad is widely distributed in the tropical and subtropical western Indian Ocean and areas of the eastern Pacific Ocean, ranging from South Africa in the west to Hawaii in the east, including Japan and Australia to the north and south. The species is commonly found on inshore reefs and sandy substrates. It has the common body profile of a scad, and may be difficult to differentiate from others in the genus Alepes. It is one of the larger scads, growing to 40 cm, but often is encountered at much smaller sizes. The shrimp scad often forms large schools, and is carnivorous, consuming a variety of crustaceans and small fish. It is of moderate importance to fisheries throughout its range.

Blackfin scad Species of fish

The blackfin scad 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. It is not a large species, with the largest reported capture being 25 cm, and it is distinguished readily from similar species by the prominent black dorsal fin. It is a predator which feeds on planktonic crustaceans, but little else is known of its biology. The blackfin scad is a minor food fish throughout its range, and is highly valued in Cambodia and Thailand.

Cleftbelly trevally Species of fish

The cleftbelly trevally, also known as the cleftbelly kingfish, Kuweh trevally or thin crevalle, is a species of tropical marine fish of the jack family, Carangidae. The species inhabits coastal waters throughout the Indo-West Pacific region from South Africa in the west to Japan in the east, often found near the water's surface. The cleftbelly trevally is the only member of the genus Atropus and is distinguished by a number of anatomical characteristics, with a deep median groove in the belly giving the species its common name. It is not a large fish, growing to a maximum recorded length of 26.5 cm. Cleftbelly trevally are predatory fish, taking a variety of small crustaceans and fish. The species is of minor importance to fisheries throughout its range.

Razorbelly scad Species of fish

The razorbelly 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 reefs. 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 its 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 crustaceans and shrimps, 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.

<i>Alepes</i> Genus of fishes

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 the larger jacks taken as game fish, although scads are generally much smaller. They are found in coastal waters throughout the Indo-West Pacific region.

Herring scad Species of fish

The herring scad, is a common species of tropical marine fish in the jack family Carangidae. The species inhabits the surface waters of coastal regions throughout the Indo-West Pacific region, feeding on a variety of crustaceans 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 scutes and the number of gill rakers on the first arch. It is of minor importance to fisheries throughout its range.

Yellowtail scad Species of fish

The yellowtail scad, is an abundant species of small inshore marine fish of the jack family, Carangidae. The species is widespread in the Indo-Pacific region from east Africa in the west to Hawaii in the east, extending north to Japan and south to Australia. The yellowtail scad is the only member of the monotypic genus Atule and is distinguished from similar species by a well-developed adipose eyelid and finlet-like extensions of the last rays of the dorsal and anal fins. It inhabits coastal areas such as bays and coral reefs, preying on small fishes and crustaceans. Spawning has been well studied in Hawaii, where fish enter bays to spawn, releasing up to 161,000 eggs each between March and October. The yellowtail scad is an important component of fisheries throughout its range, taken by a number of netting and hook-and-line methods. It is a prized food fish in some regions and is cooked or preserved by a variety of methods.

Longfin trevally Species of fish

The longfin trevally, also known as the longfin kingfish, longfin cavalla or armed trevally, is a species of inshore marine fish in the jack family, Carangidae. The species is common in tropical to subtropical waters of the Indo-Pacific, ranging from South Africa in the west to Japan in the east, typically inhabiting inshore reefs and bays. The species is easily distinguished by its elongate dorsal and anal fin lobes and filamentous dorsal rays, as well as its scaleless breast. Longfin trevally are pelagic predators, taking a variety of small fish, cephalopods and crustaceans, and reach sexual maturity at around 21 cm. The species has a maximum known length of 57 cm and weight of 3.5 kg. The longfin trevally has a very complex taxonomic history which is closely intertwined with another currently valid species, Carangoides ciliarius, which may yet prove to be synonymous. Longfin trevally are of minor importance to fisheries throughout their range and are considered good table fish, and are occasionally taken by anglers.

Longnose trevally Species of fish

The longnose trevally, also known as the tea-leaf trevally, club-nosed trevally, grunting trevally or dusky trevally, is a species of inshore marine fish in the jack family, Carangidae. The species is distributed throughout the tropical and subtropical waters of the Indian and west Pacific Oceans from South Africa to New Zealand and Japan, inhabiting coastal waters, especially reefs, to a depth of 90 m. The longnose trevally is distinguished from similar species by a combination of a scaleless breast and the number of gill rakers and fin rays. It is a moderately large fish, growing to a maximum known length of 72 cm and 4.35 kg. The longnose trevally is a predatory fish, consuming small fish, crustaceans and molluscs. The species is of minor commercial importance throughout its range, and is considered to be a good table fish.

Coastal trevally Species of fish

The coastal trevally, also known as the onion trevally, Japanese trevally or bluefin kingfish, is a species of inshore marine fish in the jack family Carangidae. The species is distributed throughout the tropical and subtropical waters of the Indian and west Pacific Oceans, from South Africa in the west to Japan and New Caledonia in the east, reaching as far south as Australia. The species is found on deep coastal reefs, both in schools and as solitary individuals, where they prey on small midwater organisms including crustaceans, small fish and cephalopods. The species is taken as bycatch in a number of fisheries throughout its range by a number of fishing methods and is of little commercial value, but is considered to be a good table fish. A mistype in the original volume in which Eduard Rüppell named the species led to the combination Carangoides caeruleopinnatus, which has incorrectly spread through the literature.

Shadow trevally Species of fish

The shadow trevally, also known as the shadow kingfish, twothread trevally or Aldabra trevally, is a species of inshore marine fish in the jack family Carangidae. The species is patchily distributed throughout the tropical and subtropical waters of the Indian and west Pacific Oceans, from South Africa in the west to Japan and Samoa in the east, reaching as far south as Indonesia and New Caledonia. It is most easily distinguished from similar species by as series of dark rectangular blotches under the second dorsal fin, giving a 'shadowed' appearance, from which its common name is derived. The shadow trevally is a reasonably large fish, growing to 85 cm in length and at least 2.6 kg in weight. It inhabits shallow coastal waters, including reefs, bays, and estuaries, where it takes small fish and benthic crustaceans as prey. Nothing is known of the species' ecology and reproductive biology. It is of little importance to fisheries, and is occasionally taken by bottom trawls and other artisanal fishing gear.

Whitefin trevally Species of fish

The whitefin trevally, also known as the horse trevally, is a species of deep water offshore fish in the jack family Carangidae. The species inhabits the tropical to temperate waters of the Indo-Pacific and central Pacific, ranging from South Africa in the west to Hawaii in the east. The whitefin trevally is a moderate-sized fish, growing to 37 cm, and is distinguished by a number of morphological traits, including fin size, gill raker count, and colour. It inhabits the continental shelf and slope at depths to 200 m over sand and mud substrates, where it preys on fish, crustaceans, and cephalopods. Studies in Japan indicate a length at sexual maturity of 17.4 cm on average, with spawning occurring between May and October, with each individual spawning multiple times. Whitefin trevallies are of high importance to fisheries in Japan, where they are taken by trawlers, although the catch numbers have halved since the 1980s. It is of minor importance elsewhere throughout its range, but is considered a good table fish.

Blue trevally Species of fish

The blue trevally, also known as the banded trevally, barred trevally, Ferdau's trevally or Forskaal's jackfish, is a common, widespread species of pelagic marine fish classified in the jack family, Carangidae. The blue trevally is distributed throughout the tropical and subtropical waters of the Indo-Pacific and central Pacific regions, ranging from South Africa in the west to Hawaii in the east. It is a moderately large fish, growing to a recorded maximum length of 70 cm, with the number of rays in the second dorsal fin and the colouring serving as diagnostic features of the species. The species inhabits waters to depths of 60 m, generally inhabiting reefs, beaches, lagoons, and areas with sandy substrates. It is a predatory fish, taking other fish, prawns, crabs, and molluscs, and very little is known of the species' reproductive biology. The blue trevally is of varying importance to fisheries throughout its range, with some regions having high catches of the fish. It is considered to be a gamefish, and is sought after for its excellent eating qualities.

Duskyshoulder trevally Species of fish

The duskyshoulder trevally or epaulet trevally, is a species of small inshore marine fish in the jack family, Carangidae. It is distributed through the eastern Indian and western Pacific Oceans, ranging from eastern India to northern Australia and Taiwan. It is relatively small by carangid standards, reaching only 27 cm maximum length, and can be distinguished by the large, black blotches on its shoulders. The duskyshoulder trevally is an inshore fish living in waters less than 50 m deep, over sandy substrates in bays and on the continental shelf. It is a predatory fish, taking demersal fishes, crustaceans, and cephalopods, with nothing known of its reproductive habits. It is of little value to fisheries, often taken as bycatch in prawn trawling operations.

Brownback trevally Species of fish

The brownback trevally, also known as the brown-backed trevally, is a species of small inshore marine fish classified in the jack family, Carangidae. The brownback trevally is distributed in two populations through the tropical waters of the Indo-west Pacific region, ranging from the Persian Gulf east to India, South East Asia and the Indonesian islands. The species is distinguished from similar species by its completely scaled breast and black-tipped second dorsal fin, and is known to reach a maximum length of 25 cm. The brownback trevally inhabits inshore waters including bays and estuaries, where it preys on demersal crustaceans and small fish. Other aspects of its biology are poorly known, and it is of minor importance to fisheries, occasionally caught by hook and line or trawls. William Smith-Vaniz has recently suggested the two distinct populations may actually represent two distinct species.

Imposter trevally Species of fish

The imposter trevally, also known as the imposter jack or white-tongued trevally, is a species of small coastal marine fish in the jack family Carangidae. The imposter trevally is distributed through the tropical waters of Indian and west Pacific oceans, from the Gulf of Oman in the west to Japan and Australia in the east. The species is quite similar to the Malabar trevally, but can be distinguished by its gill raker count, and is identifiable from other species by having a white to pale grey tongue. It is a relatively small species, growing to a maximum recorded length of 30 cm. The imposter trevally inhabits coastal waters of the continental shelf in depths of up to 140 m, often associating with closely related carangid species. It preys on a range of small fish, crustaceans and cephalopods, but little is known of its reproductive biology. The imposter trevally is of minor importance to fisheries throughout its range, taken by hook and line, bottom trawls and several types of artisanal gear.

Blacktip trevally Species of fish

The blacktip trevally, also known as the blacktip kingfish or yellowtail kingfish, is a species of large marine fish classified in the jack family Carangidae. The blacktip trevally is distributed throughout the tropical to subtropical Indian and West Pacific Oceans, ranging from South Africa in the west to Fiji, Japan and northern Australia in the east. It inhabits coastal waters throughout its range, preferring moderately deep clear waters over rocky and coral reefs. The blacktip trevally is easily distinguished by its yellow fins and a dark upper caudal fin lobe which gives the species its common name, as well as a host of other anatomical features. The species is known to reach a maximum size of 1 m. It is a benthopelagic predator, commonly forming small shoals where it takes a variety of fishes, cephalopods and crustaceans as prey. Little is known of reproduction in the species, and spawning is assumed to take place in more tropical regions of its range, with juveniles known to inhabit bays and large estuaries. Blacktip trevally are often caught using hook and line and various nets in commercial fisheries although don't make up a large part of the market. They are also popular with anglers due to their fighting ability and decent table qualities.

Senegal jack Species of fish

The Senegal jack, also known as the African jack, is a species of large marine fish classified in the jack family Carangidae. The species is distributed through the tropical waters of the eastern Atlantic Ocean, ranging along the west African coast from Angola in the south to Mauritania in the north. It can be distinguished from co-occurring relatives by its longer dorsal fin lobe, as well as a host of other anatomical features. The Senegal jack grows to a known maximum length of 1 m. It is a coastal species, known to live semi-pelagically, inhabiting both the sea floor and surface waters to depths of around 200 m. The Senegal jack is a predatory species, taking fish, crabs and shrimps as its main prey items. The species reaches sexual maturity at 21 cm in females and 24 cm in males, with spawning occurring in two periods; February to April and September to November. The species is of minor importance to fisheries, and is not discriminated from other jacks in catch statistics. It is taken by trawls, seines and hook and line, and sold fresh or preserved.

Fringefin trevally Species of fish

The fringefin trevally, also called fringe-finned trevally, round-finned trevally or reef herring, is a species of inshore marine fish classified in the jack and horse mackerel family Carangidae. A relatively small fish, the fringefin trevally is known to reach 40 cm (16 in), but is mostly encountered at lengths less than 25 cm (9.8 in). The fringefin trevally has an ovate body, with distinctive orange-yellow fins and a black opercular spot. The dental patterns of the species distinguish it from the closely related scads of the genus Alepes. Males have characteristic elongated dorsal and anal fins which produce a series of trailing filaments. The fringefin trevally is restricted to the waters of the Indo-Pacific, ranging from northern Australia to Papua New Guinea and eastern Indonesia. An inshore species, it is found in coastal and estuarine environments and exhibits daily and seasonal movements. The fringefin trevally is predatory, taking crustaceans as prey. The species is often taken as bycatch in prawn trawls and occasionally taken by anglers.

Yellowstripe scad Species of fish

The yellowstripe scad, also known as the yellowstripe trevally, yellow-banded trevally, smooth-tailed trevally, slender-scaled trevally and slender trevally, is a species of small inshore fish in the jack and horse mackerel family Carangidae, and the only member of the genus Selaroides. The yellowstripe trevally is distributed throughout the tropical waters of the Indo-West Pacific region, ranging from the Persian Gulf in the west to Vanuatu and New Caledonia in the east. The species is distinguished by its prominent lateral yellow band, and differs from the scads of the genus Selar in having a smaller eye and different dentition. The yellowstripe scad reaches a maximum recorded length of 22 cm, however is normally encountered at sizes less than 15 cm. Phylogenetic studies indicate the yellowstripe scad is closely related to the scads of the genus Selar, although its exact placement in the family Carangidae is less well agreed upon.

References

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