It is a small fish, that in our waters does not usually exceed 6 cm in length. It has three free spines and a body without scales. The caudal peduncle is very narrow and the pelvic fins are reduced to a single spine. The body color is greenish or silvery with some dark spots. Males turn red during the breeding season.

It is distributed throughout Europe. In Catalonia it is very localized in some rivers of the counties of Girona. It is also present in the Ebro delta and was formerly present in the Besòs, Llobregat and in the Salou wetlands.

It lives in slow water environments, shallow and with vegetation. It breeds between March and April. Males build a nest with plant fragments where females lay eggs that are defended by the male. They feed mainly on invertebrates.

The stickleback has suffered a very significant regression in Catalonia due to pollution, habitat alteration and the introduction of exotic species.