Featherbacks and knifefishes
Freshwater bony-tongued fishes with long anal fins
The Notopteridae family includes eleven species of slender freshwater fish found in Africa and Asia. They use a long anal fin for movement and some larger species serve as food or aquarium pets.
- Swims by rippling long anal fin
- Swim bladder absorbs air oxygen
- Fossils date to Late Cretaceous India
- Some species guard nests and eggs
- Not related to electric knifefishes
What it is
These fishes belong to the osteoglossiform group, known for their bony tongues. Their bodies are slender and elongated, creating a knife-like shape. The caudal tail fin is small and merges with the anal fin, which stretches along most of the body length. A small dorsal fin sits on the back, leading to the name featherback. They move by keeping their body stiff and rippling the long lower fin to go forward or backward.
Where it lives
Members of this family inhabit freshwater and brackish waters across two continents. Populations exist in Africa as well as in West, South, East, and Southeast Asia. They are distinct from the electric knifefishes of Central and South America, which look similar but are not closely related. The earliest fossil evidence comes from India, dating to the Late Cretaceous period roughly 66 to 70 million years ago.
How it lives
These fish possess specialized swim bladders that extend through the body and sometimes into the fins. This organ helps them absorb oxygen directly from the air. It also allows them to make sounds by forcing air through a narrow passage into the throat. While specific dietary habits vary, their unique swimming method relies on rigid body posture and fin undulation rather than tail movement.
Breeding and life cycle
Reproductive behaviour involves parental care in at least some species. Adults prepare nests for their offspring. They guard the eggs carefully until they hatch. This protective strategy helps ensure the survival of the young in their freshwater habitats. The specific timing of spawning events is not detailed in the available records.
Fish and people
Larger species, such as the clown featherback, are caught for food in certain regions. They also appear in the aquarium trade due to their unusual appearance. The common names derive from Greek words for back and fin. Care must be taken not to confuse them with South American electric knifefishes, as they are biologically different despite similar shapes.
Questions people ask about Featherbacks and knifefishes
How do featherbacks move through water?
They hold their bodies rigid and ripple their long anal fin to propel themselves forward or backward. This method gives them a distinctive gliding motion compared to fish that use their tails.
Can these fish breathe air?
Yes, their specialized swim bladder can absorb oxygen from the air. This adaptation allows them to survive in waters where dissolved oxygen levels might be low.
Are they related to electric eels?
No, although they look similar and swim in a comparable way, they are not closely related. Electric knifefishes belong to a different order found in South and Central America.
Good reading and sources
The facts on this page come from the Wikipedia article "Notopteridae", 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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