The lesser African threadfin (''Galeoides decadactylus'') is a species of marine

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 ...

which is found in the eastern Atlantic Ocean off the western coast of Africa.

Description

The lesser African threadfin has a rather compress, moderately elongated body with has a depth which is around one thirds of the

standard 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 m ...

. The mouth has an inferior position and is overhung by the blunt snout. The jaws extend past the eye. It has two

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 which are widely separated, the first dorsal fin has 8 weak spines and the second has a single spine and 13 or 14 soft rays while the anal fin has 3 spines and 11 or 12 soft rays. The second dorsal fin and anal fin have bases which are approximately equal in length. 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 ...

s are positioned low on the body, this fin has 9 or 10 detached threadlike lower rays. It has a count scales in the

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 ...

of 45–46. This species is a dull silvery colour, with a brownish to green tint in the back fading to whitish on the breast and belly. There is a large, round, dusky blotch directly below the first dorsal fin which sits beneath the lateral line at level of first dorsal fin, this blotch is similar in size to the eye. The lesser African threadfin can attain a

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 but is more normal.

Distribution

The lesser African threadfin is found in the eastern Atlantic Ocean from Morocco south as far as Angola. It is also found around the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

and

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

and has been recorded off Namibia and in the Mediterranean Sea off Algeria.

Habitat and biology

The lesser African threadfin occurs over muddy bottoms in shallow coastal waters at depths between , and they are often observed in estuaries and lagoons. Its diet is dominated by crustaceans but it will feed on small fishes. The stomach contents of specimens taken from the open sea had almost no

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

while those taken in estuaries had 31% of their stomach contents made up of detritus In a study near

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 ...

in Nigeria it was found that 25% of the females present had developed from the juvenile stage, i.e. had not been males, while the remainder had passed through a hermaphroditic phase having been males. Hermaphroditic fish are not reproductively functional. The sex composition of that population was 63.73% male, 22.22% hermaphroditic and 14.3% female.

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 ...

occurs throughout the year but peaks in the dry season and almost ceasesd during the rains. Most of these fish will not survive past the age of four years old.

Human usage

The lesser African threadfin is an important quarry species in the commercial trawl fishery of the eastern Atlantic, and it makes up between 10 and 20% of the total landings by weight. In 2000-2006 the annual catch from western Africa averaged 15,600 tonnes, with the largest catches being landed in Nigeria, Ghana, and Gabon. In Senegal, it is regarded as an important coastal resource. Fishermen use beach seines, gillnets and shallow haul nets to catch this species. The highly regarded and is marketed fresh, dried salted or smoked.

References

{{Taxonbar, from=Q2555959 Fish described in 1795 Polynemidae