Candiru Identification Guide
Learn how to recognize the candiru, a tiny, nearly transparent parasitic catfish of Amazonian rivers.
Read the full Candiru encyclopedia entry →
Key identification features
- Very small size, typically only 1-2.5 inches long, among the smallest catfish known
- Slender, semi-transparent to translucent body with little visible pigmentation
- Small, backward-pointing spines on the gill covers, used to anchor onto a host
- Eel-like, elongated shape with a small head, tiny eyes, and a narrow mouth
- Reduced fins compared to larger catfish, an adaptation for a parasitic lifestyle
- Short, fine barbels near the mouth rather than the long whiskers seen on many catfish
Common look-alikes
- Other small trichomycterid catfish: similarly slender, but generally lack the near-transparency and prominent gill-cover spines of the candiru
- Juvenile eels: share an elongated shape but have a different continuous fin arrangement and lack the catfish's barbels and gill spines
Where you'll see one
Candiru are found in the freshwater rivers and tributaries of the Amazon basin in South America, typically staying close to the gills of larger host fish rather than swimming freely in open water, which makes them rarely observed directly by people.
Frequently asked questions
How do I recognize a candiru if I spot one?
Look for its very small size, slender near-transparent body, and small backward-facing spines on the gill covers, features not shared by most other small river fish.
How is a candiru different from a juvenile eel?
The candiru has fine barbels and gill-cover spines typical of catfish, while juvenile eels lack these features and have a more uniform, continuous fin along the body.