The Gudgeon is a fish of the Cyprinidae family. It is not a game fish, yet it is a widespread species. Its native range includes the whole of Europe, except its northern and southern parts (up to the upper course of the Lena). It occurs in the Amur River basin. There are several subspecies of gudgeon. Southern ones are distinguished by bigger scales, those living in rapid rivers have protective scaling on the throat. Gudgeon usually lives in big shoals in rivers with moderate or weak currents and sandy or pebble ground, as well as in brooks and ponds with flowing water. Normally it stays in the deep water. It is known for being diurnal, normally it doesn’t move at night. Gudgeon is a typical bentophagous fish. Its diet is based on small invertebrates living on the bottom of the water body. Gudgeon also feeds on roe of other fish species. And it is preyed on by predatory fish. Its appearance is specific. The body is spindle-like, slightly flattened on the side of the belly. The scales are big. Its dorsal surface is tawny greenish, the flanks are silvery with bluish or blackish spots. The abdomen is silvery. The head is flat, eyes are turned upwards. There are dark points on dorsal and caudal fins. Such coloring enables gudgeon to disguise itself on the ground. Its snout is elongated, its lower jaw is shorter, than the upper one, there are barbels on the corners of its mouth. Gudgeon, swimming in the water, may be easily recognized by its pectoral fins spread side-wards, endowing its outline with a triangular shape. The gudgeon is a small fish, its size seldom exceeds 15 cm.