The smallmouth scad (''Alepes apercna'') (also known as the banded scad and roundfin trevally), is a species of tropical

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

fish Fish are aquatic, craniate, gill-bearing 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. Approximately 95% of li ...

in the jack family Carangidae. The species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to northern Australia, inhabiting primarily inshore waters. It is similar to other scads in the genus ''

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 ...

'', and is distinguished by a well-developed posterior

adipose eyelid An adipose eyelid is a transparent eyelid found in some species of fish, that covers some or all of the eye. They are most commonly found on deep sea (benthic) fish, but can also be seen on non-benthic fish. Fish with this feature include milkfish ...

, 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

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s, and is of very minor economic importance.

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 Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Carangiformes Carangiformes is an order of the ray-finned fishes. The order is part of a clade which is a sister clade to the Ovalentaria, the other orders in the clade being Synbranchiformes, Anabantiformes, Istiophoriformes and Pleuronectiformes. The Carang ...

. 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 Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

was taken in 1984, and deposited in the Queensland Museum along with photographs of a juvenile as paratypes with no

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

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 The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...

rules. 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. The

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

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.

Description

The smallmouth scad has an elongate oval to

oblong An oblong is a non-square rectangle. Oblong may also refer to: Places * Oblong, Illinois, a village in the United States * Oblong Township, Crawford County, Illinois, United States * A strip of land on the New York-Connecticut border in the Unit ...

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. 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

spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolog ...

s, and the second dorsal has one spine and 24-26

soft ray Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology co ...

s. 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. 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 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 ...

counts, having 27-30 compared to ''A. vari's'' 37. The largest specimen known was taken by the

CSIRO The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government The Australian Government, also known as the Commonwealth Government, is the national government of Australia, a federal parliamentar ...

and measured 29.5 cm. 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 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 se ...

are a dusky yellow green. The anterior of the soft dorsal and anal fins have white tips and 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 en ...

is a white to grey colour, while the pectoral is

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

Distribution and habitat

The smallmouth scad is known only from Australian waters, inhabiting the tropical north from

Exmouth Gulf Exmouth Gulf is a gulf in the north-west of Western Australia. It lies between North West Cape and the main coastline of Western Australia. It is considered to be part of the Pilbara Coast and Northwest Shelf, and the Carnarvon Basin geologi ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

, north to the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

and east to Wide Bay in

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

. There has been a single report of an individual as far down as

Botany Bay Botany Bay (Dharawal: ''Kamay''), an open oceanic embayment, is located in Sydney, New South Wales, Australia, south of the Sydney central business district. Its source is the confluence of the Georges River at Taren Point and the Cook ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. The species may also occur in the Gulf of Papua but has not yet reported. It is an abundant fish on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

in waters from 10 to 150 m in depth, rarely leading a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

lifestyle.

Biology and fishery

Smallmouth scad are omnivorous, but take a high proportion of small

s, primarily benthic

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s and

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s. It also frequently ingests

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, a feature which is rare in the Carangidae. Nothing of the reproductive cycle is known. It is of little importance to

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

, usually caught on hook and line tackle by commercial and

recreational Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or pleasure ...

fishermen.

References

External links

Smallmouth scad at FishbaseBasic summary and school photo
{{Taxonbar, from=Q603674 Alepes Fish described in 1987 vi:Carpiodes cyprinus