Fourfinger threadfin
A large marine threadfin found in the Indo-Pacific.
The fourfinger threadfin is a marine fish from the Polynemidae family. It lives in coastal waters across the Indian and western Pacific Oceans. This species is valued for food and aquaculture, though populations in the Persian Gulf face decline.
- Can grow up to 2 metres in length
- Starts life as a male before changing sex
- Highly valued in Kuwaiti and Iranian markets
- Juveniles live in estuaries and tidal swamps
- Has four distinct filaments on pectoral fins
What it is
This ray-finned fish belongs to the threadfin family. It features two dorsal fins, with the first containing nine spines. The second dorsal fin holds between thirteen and fifteen soft rays. Four distinct filaments extend from the pectoral fins. Small individuals display vivid yellow membranes on these fins, which darken as the fish grows. The body has a darkish silver tone on top, fading to lighter flanks below. While it can reach two metres in length, most adults measure around fifty centimetres.
Where it lives
Its distribution spans the Indo-Pacific region. You can find it from the Persian Gulf eastward to Australia and Papua New Guinea. Adults prefer shallow coastal areas with muddy bottoms. They often enter river systems during winter months. Juveniles stay in estuarine environments. These fish use lower estuaries, tidal swamps, and lagoons as nursery grounds. They also inhabit the shallow waters along foreshores.
How it lives
Adults usually swim in loose schools, though larger specimens may appear in pairs or alone. This carnivorous species hunts prawns and other fish. Common prey includes grey mullets, anchovies, and drums. They also eat polychaete worms. The diet shifts with seasons, changing the ratio of crustaceans to fish. Larvae feed mainly on copepods and mysids. Larger juveniles target prawns and small decapods.
Breeding and life cycle
This species is a protandrous hermaphrodite, meaning it starts life as a male. Fish become hermaphrodites at one to two years old. Females appear at two to three years of age. Males likely change sex after spawning in April and May. They remain hermaphroditic until the next breeding season ends, then develop into females. Most fish over forty-five centimetres long off Queensland are female.
Fish and people
Fisheries value this species highly. It is sold fresh, frozen, dried, or salted. Aquaculture operations also raise this fish. In Kuwait and Iran, it commands high prices in markets. It serves as a key commercial catch in Kuwait, though some are taken as bycatch. Local names vary widely, including rawas in India and blue threadfin in Australia.
Status and threats
The global conservation status has not been evaluated by the IUCN. However, populations in the Persian Gulf are classified as Endangered. Data suggests these local numbers are declining rapidly. No broader protection measures are detailed in the available information.
Questions people ask about Fourfinger threadfin
What does the fourfinger threadfin eat?
It is a carnivore that preys on prawns, fish like grey mullets and anchovies, and polychaete worms. Larvae feed on copepods and mysids.
Where is this fish found?
It has an Indo-Pacific distribution, ranging from the Persian Gulf to Australia and Papua New Guinea, living in coastal muddy substrates.
Is the fourfinger threadfin endangered?
Its global status is not evaluated, but it is classified as Endangered in the Persian Gulf due to rapid population decline there.
How does this fish reproduce?
It is a protandrous hermaphrodite. Fish start as males, become hermaphrodites at one to two years, and turn into females by two to three years.
Good reading and sources
- Eleutheronema tetradactylum on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Eleutheronema tetradactylum", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
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