Duskyshoulder trevally
Encyclopedia
The duskyshoulder trevally, Carangoides humerosus (also known as the epaulet trevally), is a species
of small inshore marine
fish
in the jack family, Carangidae
. The duskyshoulder trevally is distributed through the eastern Indian
and western Pacific Ocean
s, 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 bay
s and on the continental shelf
. It is a predatory fish, taking demersal fishes, crustacean
s and cephalopod
s, with nothing known of its reproductive habits. It is of little value to fisheries, often taken as bycatch in prawn
trawling operations.
, a group of fish commonly called jacks and trevallies. Carangoides falls into the jack and horse mackerel family Carangidae
, itself part the order Perciformes
, in the suborder Percoidei
.
The species was first scientifically described by the Australian ichthyologist Alan Riverstone McCulloch
in 1915 based on the holotype
specimen taken from Bustard Head in Queensland
, Australia. He named the species Caranx humerosus, with the specific epithet literally meaning "having shoulders" in reference to the species prominent dark shoulder colouring. The species was later transferred to the genus Carangoides, where it has remained to this day. The species has not been redescribed under another name, which is rare amongst the Carangidae. The common name
of 'duskyshoulder trevally ' refers to the prominent shoulder markers, as does the name 'epaulet trevally'.
s contain anteriorly widening bands of small villiform teeth, with older individuals also having a number of larger outer teeth. There are two separate dorsal fin
s, the first consisting of 8 spines and the second of 1 spine and 20 to 22 soft rays. The anal fin comprises two detached anterior spines, followed by 1 spine and 17 to 19 soft rays. The lobe of the soft dorsal fin is falcate, being about the same length as the head. The pelvic fin consists of 1 spine and 18 or 19 soft rays. The lateral line is moderately curved anteriorly, with the curve having 62 to 72 scales present on it, while the straight section contains 3 to 8 scales and 24 to 32 scutes. The breast of the duskyshoulder trevally is scaleless, extending up to behind the pelvic fin origin and laterally to the pectoral fin base. There are 6 to 10 gill raker
s on the first arch and 16 to 20 on the second arch, and the species has 24 vertebrae.
The duskyshoulder trevally is a dusky green colour above, fading to silver below, with adults and juveniles often having 5 or 6 dark broad cross bars running vertically down their body. There is a large black spot usually present on the shoulder, with smaller dark spots on the operculum
and pectoral fin axil. The soft dorsal, anal and caudal fins are dusky, with the spinous dorsal fin black. The pectoral and pelvic fins are hyaline
to white in colour.
and west Pacific Ocean
, recorded only from the coastlines of India
, Indonesia
, Papua New Guinea
, northern Australia
and possibly Taiwan
. The species probably inhabits more island nations in the region, but due to inadequate sampling has not been recorded.
The species lives in waters shallower than 50 m, generally inhabiting the sand
y substrates
and reef
s of the continental shelf
, also venturing into bay
s and inhabiting beach
es and mangrove
-lined creeks.
, Australia indicating it preys mostly on various species of small teleost fish and crustacean
s, with particular preference for brachyurans. Other less common prey taken includes penaeid prawns, other crustaceans, molluscs and cephalopod
s. Nothing is known of the movements or reproduction in the species.
The duskyshoulder trevally is of little importance to either commercial fisheries or angler
s, but is commonly taken as bycatch in other trawl related fisheries, especially the northern Australian prawn fishery. It is mostly discarded when taken, rarely sold at market.
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 small inshore marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
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 duskyshoulder trevally is distributed through the eastern Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and western Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s, ranging from eastern 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...
to northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
. 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 bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s and on the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
. It is a predatory fish, taking demersal fishes, 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 cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, with nothing known of its reproductive habits. It is of little value to fisheries, often taken as bycatch in prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
trawling operations.
Taxonomy and naming
The duskyshoulder trevally is classified within the genus CarangoidesCarangoides
Carangoides is a genus of tropical to subtropical marine fishes in the jack family, Carangidae. They are small to large sized, deep bodied fish characterised by a certain gill raker and jaw morphology, often appearing very similar to jacks in the genus Caranx...
, a group of fish commonly called jacks and trevallies. Carangoides falls into the jack and horse mackerel 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...
, itself part the order Perciformes
Perciformes
The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
, 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 Australian ichthyologist Alan Riverstone McCulloch
Alan Riverstone McCulloch
Alan Riverstone McCulloch was a prominent Australian ichthyologist.McCulloch was born in Sydney, and began his scientific career at the age of 13 as an unpaid assistant to Edgar Ravenswood Waite in the Australian Museum there; Waite encouraged McCulloch to study zoology...
in 1915 based on the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen taken from Bustard Head in Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, Australia. He named the species Caranx humerosus, with the specific epithet literally meaning "having shoulders" in reference to the species prominent dark shoulder colouring. The species was later transferred to the genus Carangoides, where it has remained to this day. The species has not been redescribed under another name, which is rare amongst the Carangidae. The common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
of 'duskyshoulder trevally ' refers to the prominent shoulder markers, as does the name 'epaulet trevally'.
Description
The duskyshoulder trevally is one of the smallest fish in the genus Carangoides, reaching only 27 cm in length. The species is similar to other jacks in its overall body profile, having a compressed ovate to oblong shape, with the dorsal profile more convex than the ventral profile. The head profile is gently sloping and slightly convex, with large males having a distinct bulge that is absent in females and juveniles of both sexes. Both of the jawJaw
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 contain anteriorly widening bands of small villiform teeth, with older individuals also having a number of larger outer teeth. There are two separate dorsal fin
Dorsal 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 consisting of 8 spines and the second of 1 spine and 20 to 22 soft rays. The anal fin comprises two detached anterior spines, followed by 1 spine and 17 to 19 soft rays. The lobe of the soft dorsal fin is falcate, being about the same length as the head. The pelvic fin consists of 1 spine and 18 or 19 soft rays. The lateral line is moderately curved anteriorly, with the curve having 62 to 72 scales present on it, while the straight section contains 3 to 8 scales and 24 to 32 scutes. The breast of the duskyshoulder trevally is scaleless, extending up to behind the pelvic fin origin and laterally to the pectoral fin base. There are 6 to 10 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 and 16 to 20 on the second arch, and the species has 24 vertebrae.
The duskyshoulder trevally is a dusky green colour above, fading to silver below, with adults and juveniles often having 5 or 6 dark broad cross bars running vertically down their body. There is a large black spot usually present on the shoulder, with smaller dark spots on the 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....
and pectoral fin axil. The soft dorsal, anal and caudal fins are dusky, with the spinous dorsal fin black. The pectoral and pelvic fins are hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
to white in colour.
Distribution and habitat
The duskyshoulder trevally inhabits the tropical and subtropical regions of the eastern Indian OceanIndian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and west Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, recorded only from the coastlines of 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...
, 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...
, Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
, northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and possibly Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
. The species probably inhabits more island nations in the region, but due to inadequate sampling has not been recorded.
The species lives in waters shallower than 50 m, generally inhabiting the sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
y substrates
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
and reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s of the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
, also venturing into bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s and inhabiting beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es and mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
-lined creeks.
Biology and fishery
The duskyshoulder trevally is poorly studied in most aspects of its biology with the exception of its diet. It is a benthic predator, with studies in the Gulf of CarpentariaGulf of Carpentaria
The Gulf of Carpentaria is a large, shallow sea enclosed on three sides by northern Australia and bounded on the north by the Arafura Sea...
, Australia indicating it preys mostly on various species of small teleost fish and 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, with particular preference for brachyurans. Other less common prey taken includes penaeid prawns, other crustaceans, molluscs and cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s. Nothing is known of the movements or reproduction in the species.
The duskyshoulder trevally is of little importance to either commercial fisheries or angler
Angling
Angling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
s, but is commonly taken as bycatch in other trawl related fisheries, especially the northern Australian prawn fishery. It is mostly discarded when taken, rarely sold at market.