The Atlantic threadfin (''Polydactylus octonemus'') 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 ...

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 native to subtropical and temperate waters of the western

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

Description

The Atlantic threadfin is a medium-sized species of threadfin which grows to 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 most fish have a total length of around . It has a pointed snout and an almost straight dorsal profile on its head. There are 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 contains 8 spines in which the bases of each spine is a similar thickness to the others, and the second dorsal fin has a single spine and 11 to 13 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 ...

has 3 spines and 12 to 14 soft rays, The base of the

is longer than that of the second dorsal fin. The pectoral fin has 14 to 16 unbranched rays and has a length equivalent to 24%-29% of the standard length and its tip does not reach the tip of pelvic fin. There are 8 pectoral filaments 8, sometimes 9, and the first pectoral filament is the shortest, extending beyond level of front of 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 ...

while the second to fifth pectoral filaments reach slightly farther while the sixth filament may extend slightly beyond the tip of the pelvic fin. The seventh pectoral filament does not extend as far as the anal-fin origin. The eighth pectoral filament is the longest and it has a length equivalent to 39% to 51% of the standard length. The filaments tend to be longer in adults than they are in young fish. The caudal fin is deeply forked with its upper and lower caudal-fin lobes not bearing filaments. There are 56-64 pored 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 ...

which is forked on the caudal fin, with branches reaching onto the rear margin of the lobes of the tail. The upper sides of the head and the flanksare tinged with a slight darkish silver shade, lightening on the lower flanks. It has a semi-translucent snout. The first and second dorsal fins are coloured dusky yellow; the pectoral fin is black while the pectoral filaments are translucent. The dusk yellow anal fin has a white rear margin. The caudal fin is dusky yellowish with a black rear margin.

Distribution

The Atlantic threadfin is found in the western Atlantic where it occurs from

New Smyrna Beach New Smyrna Beach is a city in Volusia County, Florida, United States, located on the central east coast of the state, with the Atlantic Ocean to the east. Its population is 30,142 in 2020 by the United States Census Bureau. The downtown section o ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

south and west into the

coast of the United Statesto the Yucatan Peninsula in Mexico. It is absent from the northern part of the Yucatan Peninsula and from Cuba.

Vagrants Vagrancy is the condition of homelessness without regular employment or income. Vagrants (also known as bums, vagabonds, rogues, tramps or drifters) usually live in poverty and support themselves by begging, scavenging, petty theft, temporar ...

stray as far north as

Long Island Long Island is a densely populated island in the southeastern region of the U.S. state of New York (state), New York, part of the New York metropolitan area. With over 8 million people, Long Island is the most populous island in the United Sta ...

Habitat and biology

The Atlantic threadfin occurs over sandy or muddy bottoms and on beaches, commonly being observed in the surf zone. It occurs at depths between in the Gulf of Mexico but peak numbers are found at depths of . Young specimens, of lengths less than have been taken from the surface of the Gulf of Mexico where the sea was . Sexual maturity is reached at total lengths between , when they are around 7 to 9 months of age.

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 ...

probably occurs in the Gulf of Mexico, off

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

and

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and mainly takes place between mid-December and mid-March and lasts between 45 and 120 days overall. The 2-4 month old larvae live in waters shallower than , dispersing towards deeper waters in the early summer. They typically live no longer then 1 year but may be longer in fish that survive their first pelagic spawning.

Species description

The Atlantic threadfin was originally formally described as ''Polynemus octonemus'' in 1858 by Charles Frédéric Girard with the type locality of

Brazos Santiago Brazos Island, also known as Brazos Santiago Island, is a barrier island on the Gulf Coast of Texas in the United States, south of the town of South Padre Island. The island is located in Cameron County. Brazos Santiago Pass partitions the bar ...

, and

Galveston Galveston ( ) is a coastal resort city and port off the Southeast Texas coast on Galveston Island and Pelican Island in the U.S. state of Texas. The community of , with a population of 47,743 in 2010, is the county seat of surrounding Galvesto ...

, Texas.

References

{{Taxonbar, from=Q3753546 Atlantic threadfin Taxa named by Charles Frédéric Girard Fish described in 1858