Senegal jack
Encyclopedia
The Senegal jack, Caranx senegallus (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 Africa
n 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, crab
s and shrimp
s 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, seine
s and hook and line, and sold fresh or preserved.
, one of a number of groups known as the jacks or trevallies. Caranx itself is part of the larger jack and horse mackerel family Carangidae
, a group of percoid
fishes in the order Perciformes
.
The species was first scientifically described by the famed French naturalist
Georges Cuvier
in 1833 based on a specimen taken from the mouth of the Senegal River
at Gorée
, Senegal, which was designated to be the holotype
. Cuvier named the new species Caranx senegallus with the specific epithet referring to the country the holotype was taken from. The species was independently redescribed twice; both times by the Austrian zoologist Franz Steindachner
. In 1867 he named the species Caranx macrops, while in 1883 he named it Caranx africanus, with no apparent reason for the redescription. Under ICZN
naming rules, these are both considered junior synonyms and rendered invalid. The species' two common name
s simply refer to the African coasts where the species is found.
but is more common at around 30 cm. It has a body shape typical of most other species of Caranx, with a moderately compressed ovate form and blunt pointed snout. The dorsal profile is slightly more convex than the ventral profile. The dorsal fin
is in two distinct sections, the first consisting of 8 spines while the second has 1 spine and 20 or 21 soft rays. The anal fin consists of 2 detached spines anteriorly followed by 1 spine and 17 or 18 soft rays. Both the anal and dorsal fins are elongate, with the dorsal lobe being over twice the length of the head. The pectoral fin is falcate, and also longer than the head. The lateral line
has a short, strong anterior arch, with 40 to 45 scute
s on the straight posterior section. Above and below the terminus of the lateral line on the caudal peduncle are bilateral caudal keel
s. The rest of the body is covered in small cycloid scale
s, with the exception of the breast which is naked. The Senegal jack's eye has a weakly developed adipose eyelid, with the end of the upper jaw
extending to directly under the middle of the eye. The upper jaw contains an inner band of villiform teeth with an irregular series of outer canines, while the lower jaw contains only a band of villiform teeth. The species has 38 to 42 gill raker
s and 24 vertebrae.
The Senegal jack is a green to blue colour dorsally, fading to a silvery white below. The fins are hyaline
to grey, with the pectoral fin and anal fin lobe having a pale yellow tinge. The species has a black spot on the upper opercular
margin.
, ranging along the west Africa
n coast from Angola
in the south to Mauritania
in the north.
The Senegal jack is an inshore species, living semi-pelagically, moving between surface and bottom layers in coastal waters. It is confidently known to range to a depth of at least 90 m, although may live at depths of around 200 m. Older fish tend to live further from the shore on reef
s, while juveniles inhabit shallow tidal bay
s and creek
s lined with mangrove
s. The species is also known to occur in estuaries in significant numbers, inhabiting these on a semi-permanent basis.
s and shrimp
s. The species shows a difference in age of maturation
between the sexes, with males reaching sexual maturity at 24 cm and females at 21 cm. Spawning
has been documented in Guinea Bissau during two peaks throughout the year; the first occurring from February to April and the second from September to November. Spawning occurs in shallow waters, with larva
e and juveniles known to inhabit shallow tidal creeks and estuaries. The juveniles migrate back to the deeper marine environment as they grow.
The Senegal jack is of minor importance to fisheries throughout its range, although individual fisheries statistics are not available for the species, so its exact importance can not be quantified. It is taken using trawls, purse seines and hook and line gear, and is generally counted with other species of Caranx in a catch. Senegal jack is sold fresh, frozen, salted
and smoked as well as being used for fish meal
and oil. The species is also considered a gamefish in larger sizes.
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 large 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...
classified 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 species is distributed through the tropical waters of the eastern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, ranging along the west Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
n coast from Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
in the south to Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
in the north. It can be distinguished from co-occurring relatives by its longer 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...
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, crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s as its main prey items. The species reaches sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at 21 cm in females and 24 cm in males, with spawning
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called 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, seine
Seine
The Seine is a -long river and an important commercial waterway within the Paris Basin in the north of France. It rises at Saint-Seine near Dijon in northeastern France in the Langres plateau, flowing through Paris and into the English Channel at Le Havre . It is navigable by ocean-going vessels...
s and hook and line, and sold fresh or preserved.
Taxonomy and naming
The Senegal jack is classified within the genus CaranxCaranx
Caranx is a genus of tropical to subtropical marine fish in the jack family Carangidae, commonly known as jacks, trevallies and kingfishes. They are moderate to large sized, deep bodied fishes which are distinguished from other carangid genera by specific gill raker, fin ray and dentition...
, one of a number of groups known as the jacks or trevallies. Caranx itself is part of the larger 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...
, a group of percoid
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:...
fishes in 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...
.
The species was first scientifically described by the famed French naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
in 1833 based on a specimen taken from the mouth of the Senegal River
Sénégal River
The Sénégal River is a long river in West Africa that forms the border between Senegal and Mauritania.The Sénégal's headwaters are the Semefé and Bafing rivers which both originate in Guinea; they form a small part of the Guinean-Malian border before coming together at Bafoulabé in Mali...
at Gorée
Gorée
Île de Gorée Île de Gorée Île de Gorée (i.e. "Gorée Island"; is one of the 19 communes d'arrondissement (i.e. "commune of arrondissement") of the city of Dakar, Senegal. It is a island located at sea from the main harbor of Dakar ....
, Senegal, which was designated to be 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...
. Cuvier named the new species Caranx senegallus with the specific epithet referring to the country the holotype was taken from. The species was independently redescribed twice; both times by the Austrian zoologist Franz Steindachner
Franz Steindachner
Franz Steindachner was an Austrian zoologist.- Work and career :Being interested in natural history, Steindachner took up the study of fossil fishes on the recommendation of his friend Eduard Suess...
. In 1867 he named the species Caranx macrops, while in 1883 he named it Caranx africanus, with no apparent reason for the redescription. Under ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
naming rules, these are both considered junior synonyms and rendered invalid. The species' two 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...
s simply refer to the African coasts where the species is found.
Description
The Senegal jack is a large species of fish, known to reach a length of 1 m,but is more common at around 30 cm. It has a body shape typical of most other species of Caranx, with a moderately compressed ovate form and blunt pointed snout. The dorsal profile is slightly more convex than the ventral profile. The 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...
is in two distinct sections, the first consisting of 8 spines while the second has 1 spine and 20 or 21 soft rays. The anal fin consists of 2 detached spines anteriorly followed by 1 spine and 17 or 18 soft rays. Both the anal and dorsal fins are elongate, with the dorsal lobe being over twice the length of the head. The pectoral fin is falcate, and also longer than the head. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
has a short, strong anterior arch, with 40 to 45 scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s on the straight posterior section. Above and below the terminus of the lateral line on the caudal peduncle are bilateral caudal keel
Keel
In boats and ships, keel can refer to either of two parts: a structural element, or a hydrodynamic element. These parts overlap. As the laying down of the keel is the initial step in construction of a ship, in British and American shipbuilding traditions the construction is dated from this event...
s. The rest of the body is covered in small cycloid scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s, with the exception of the breast which is naked. The Senegal jack's eye has a weakly developed adipose eyelid, with the end of the upper jaw
Jaw
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...
extending to directly under the middle of the eye. The upper jaw contains an inner band of villiform teeth with an irregular series of outer canines, while the lower jaw contains only a band of villiform teeth. The species has 38 to 42 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 and 24 vertebrae.
The Senegal jack is a green to blue colour dorsally, fading to a silvery white below. The 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 grey, with the pectoral fin and anal fin lobe having a pale yellow tinge. The species has a black spot on the upper opercular
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....
margin.
Distribution and habitat
The Senegal jack has a relatively restricted range compared to most of the other members of Caranx. It is distributed through the tropical waters of the eastern Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, ranging along the west Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
n coast from Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
in the south to Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
in the north.
The Senegal jack is an inshore species, living semi-pelagically, moving between surface and bottom layers in coastal waters. It is confidently known to range to a depth of at least 90 m, although may live at depths of around 200 m. Older fish tend to live further from the shore on reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, while juveniles inhabit shallow tidal 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 creek
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
s lined with 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...
s. The species is also known to occur in estuaries in significant numbers, inhabiting these on a semi-permanent basis.
Biology and fishery
The Senegal jack is a predatory fish, taking a variety of small fishes, crabCrab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s. The species shows a difference in age of maturation
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
between the sexes, with males reaching sexual maturity at 24 cm and females at 21 cm. Spawning
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
has been documented in Guinea Bissau during two peaks throughout the year; the first occurring from February to April and the second from September to November. Spawning occurs in shallow waters, with larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e and juveniles known to inhabit shallow tidal creeks and estuaries. The juveniles migrate back to the deeper marine environment as they grow.
The Senegal jack is of minor importance to fisheries throughout its range, although individual fisheries statistics are not available for the species, so its exact importance can not be quantified. It is taken using trawls, purse seines and hook and line gear, and is generally counted with other species of Caranx in a catch. Senegal jack is sold fresh, frozen, salted
Salting (food)
Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...
and smoked as well as being used for fish meal
Fish meal
Fish meal, or fishmeal, is a commercial product made from both whole fish and the bones and offal from processed fish. It is a brown powder or cake obtained by rendering pressing the cooked whole fish or fish trimmings to remove most of the fish oil and water, and then ground...
and oil. The species is also considered a gamefish in larger sizes.