The royal threadfin (''Pentanemus quinquarius'') is a species of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

, a

threadfin Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name ...

from the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Polynemidae Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name ...

, the

s. It is found in the eastern Atlantic Ocean along the western coast of Africa.

Description

The royal threadfin is a medium-sized threadfin species reaching a maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of , although a more normal length is . It has two separate

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s, the first dorsal fin has 8 spines and the second dorsal fin has a single spine and 14 or 15 soft rays. The

anal 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 ...

contains 3 spines and 24 to 30 soft rays, with a base which is longer than that of the second dorsal-fin. The

pectoral 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 ...

has 14 to 16 unbranched rays and is 30% to 42% of the fish's standard length with its tip extending to or just short of the centre of the base of the

. The pectoral fin is situated far below the midline of body. There are 5 pectoral filaments, the first being the shortest and this filament just reaches to or extends beyond the start of the anal fin. The remaining pectoral filaments reach well past the ends of lobes of the

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 ...

s with the third filament being the longest being 2.5-3 times the standard length. The caudal fin is deeply forked and the lobes are not fialmented, the length of the upper lobe is 36% to 46% of the standard length and lower lobe is 38 %to 47% of the standard length. There are 68-76 pored scales in the simple

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 epithelial ...

which extends from upper end of gill opening to the middle of the caudal fin fork. The upper sides of its head and body tinged with gold, this changes to silver on the lower flanks. The margins of both dorsal fins and the caudal fins are black, the rest of these fins are blackish while pelvic and anal fins are white. The pectoral fin is yellow with

melanophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, ...

s. The base of pectoral filaments is white, darkening towards their tips.

Distribution

The royal threadfin is found in the eastern Atlantic Ocean where it occurs along the western coast of Africa from Senegal to Angola. It has been recorded from

Cape Verde , national_anthem = () , official_languages = Portuguese , national_languages = Cape Verdean Creole , capital = Praia , coordinates = , largest_city = capital , demonym ...

and Mauritania. A record from Cuba of a half grown fish from the mid-nineteenth century remains the only record from the western Atlantic Ocean.

Habitat and biology

The royal threadfin occurs over muddy substrates in shallow coastal waters between in depth. It is also often recorded in estuaries and lagoons. It is a carnivorous fish and its diet consists of crustaceans and small fish.

Spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...

takes place off

Lagos Lagos (Nigerian English: ; ) is the largest city in Nigeria and the List of cities in Africa by population, second most populous city in Africa, with a population of 15.4 million as of 2015 within the city proper. Lagos was the national ca ...

throughout the year but peaks in the dry season and nearly stops altogether during the rainy season. Unlike other threadfins this species has a small proportion of the population which are hermaphroditic. It is also relatively short lived and few fish survive beyond 2 years of age.

Fisheries

The royal threadfin is mainly taken as

by-catch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

off Lagos by shrimp beam trawlers, but it is still commercially important. Most of the fish caught are subadults and this pattern is likely replicated throughout West Africa where it is one of the most important commercial species in this region> It is caught using trawls, but also by gillnet and beach seine. In Senegal, it is regarded as less valuable due to its smaller size and lower abundance than the

lesser African threadfin The lesser African threadfin (''Galeoides decadactylus'') is a species of marine ray-finned fish, a threadfin from the family Polynemidae which is found in the eastern Atlantic Ocean off the western coast of Africa. Description The lesser Afric ...

References

{{Taxonbar, From = Q2196051 Polynemidae Fish described in 1758 Taxa named by Carl Linnaeus Taxobox binomials not recognized by IUCN