The size of the adults is 40-80 cm; males are smaller than females. The body is very elongated and covered with a thick mucous layer, under which there are very small scales. Young eels in the growth phase are called "yellow eels" and have a brown coloration with a yellow belly.. When they migrate to the sea they transform into "silver eels", taking on a grayish coloration with silvery hues.

The eel is found in all river basins in Europe and North Africa that are connected to the sea. Their distribution is limited by the presence of dams and other barriers that prevent them from being able to go upstream.

It is a catadromous species, which breeds in the Sargasso Sea, in the Atlantic Ocean near Central America, from where it migrates to the coasts of Europe and enters inland waters. Small eels enter rivers mainly in late fall and winter. They remain in the rivers between 4 and 12 years before returning to the sea for breeding. It is mainly nocturnal and feeds on insects, crustaceans, mollusks and small fish.

The eel is in critical danger of extinction, as it has suffered a sharp decline in recent decades due to dams and other obstacles preventing their migrations, overfishing and pollution by organic compounds (PCB).