Gudgeon

The gudgeon (Gobio gobio) is a small fish common in Europe, where it inhabits fast-flowing as well as still waters and canals.
It is a gregarious fish, which swims in schools and is able to communicate with others by emitting squeaking sounds.

It is usually diurnal, although it can change its habits if threatened by a predator. Gudgeons feed on small mollusks, aquatic worms, and crustaceans such as copepods, all of which they find on riverbeds. They spawn between April and August. Gudgeons are very vulnerable to pollution.

The caption reads in the original French: Goujon commun (Gobio fluviatilis).