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Royal threadfin
Pentanemus quinquarius - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - UBA01 IZ13400129.tif
Conservation status
Scientific classification
Synonyms
  • Polynemus quinquarius Linnaeus, 1758
  • Polynemus artedii Bennett, 1831
  • Polynemus macronemus Pel, 1851
  • Polynemus peli Njock, 1990

The royal threadfin (Pentanemus quinquarius) is a type of fish that lives in the ocean. It belongs to a group of fish called threadfins. You can find this fish in the eastern Atlantic Ocean, mostly along the western coast of Africa.

About the Royal Threadfin

The royal threadfin is a medium-sized fish. It can grow up to 35 centimetres (14 in) long, which is about the length of a school ruler. Most royal threadfins are around 25 centimetres (9.8 in) long.

What Does It Look Like?

This fish has two separate fins on its back, called dorsal fins. The first dorsal fin has 8 stiff spines. The second dorsal fin has one spine and 14 or 15 soft rays.

Its anal fin (on its belly) has 3 spines and 24 to 30 soft rays. This fin is longer than the second dorsal fin. The pectoral fins (on its sides) have 14 to 16 rays and are quite long. They reach almost to the middle of the anal fin.

A special feature of the royal threadfin is its 5 long, thread-like feelers near its pectoral fins. The first feeler is the shortest. The third feeler is the longest, reaching up to 3 times the fish's body length!

The tail fin, called the caudal fin, is deeply forked, like a "V" shape. Its upper and lower parts are almost the same length. The fish has a lateral line with 68-76 scales. This line helps the fish sense movements in the water.

Colors of the Royal Threadfin

The top of its head and body are a shiny gold color. This changes to silver on its lower sides. The edges of its dorsal fins and tail fin are black. The rest of these fins are dark. Its pelvic and anal fins are white. The pectoral fins are yellow with dark spots. The long feelers start white and get darker towards their tips.

Where Royal Threadfins Live

The royal threadfin lives in the eastern Atlantic Ocean. It is found along the western coast of Africa, from Senegal all the way to Angola. It has also been seen near Cape Verde and Mauritania. There was one rare sighting in Cuba a long time ago, but it's usually found only in the eastern Atlantic.

Habitat and Life Cycle

Royal threadfins like to live in shallow coastal waters. They prefer areas with muddy bottoms, usually between 10 and 70 metres (33 and 230 ft) deep. You can also often find them in estuaries (where rivers meet the sea) and lagoons.

What Do They Eat?

This fish is a carnivore, meaning it eats other animals. Its diet mainly includes small crustaceans, like shrimp, and other small fish.

Reproduction

Royal threadfins lay their eggs, a process called spawning, all year round near Lagos, Nigeria. However, they spawn most often during the dry season. They almost stop spawning completely during the rainy season.

Unlike many other fish, some royal threadfins are hermaphroditic. This means they have both male and female reproductive parts. These fish do not live very long; most of them do not survive past 2 years old.

Fishing for Royal Threadfins

The royal threadfin is an important fish for local fishing. It is often caught by accident when people are fishing for shrimp using special nets called beam trawlers. This is known as by-catch.

Even though it's often caught as by-catch, it's still very important for people who fish in West Africa. It is caught using trawls (large nets pulled by boats), gillnets, and beach seines (nets pulled from the shore). In Senegal, it is considered less valuable than another type of threadfin because it is smaller and less common there.

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