The asp has a long, compressed body on the side, slightly silvery brown. It can reach 1 m in length, but usually do not exceed 60 cm. The head is prominent with the lower jaw protruding from the upper.

It is distributed throughout Europe and Asia. In Catalonia it has recently been introduced in the Muga basin.

It lives in large slow-flowing rivers, lakes and reservoirs. They feed mainly on fish, but it also preys on amphibians and crayfish. They spawn in running water on gravel or submerged vegetation.