The grayling (Thymallus thymallus) is characterized by a perfect hydrodynamic shape, a tapered body, olive back, silver sides with yellow and orange parts, sometimes spotted with black dots, with a wide dorsal fin with iridescent nuances. The grayling’s mouth is small, just like its teeth. It measures about 30 cm and weighs 200-300 gr. It rarely exceeds 50 cm and a 1kg weight. Clear, well-oxygenated rivers and streams, not too rapid, and with a stony or gravel bed, represent the favorite habitat of the grayling. It feeds on insects and small aquatic and terrestrial invertebrates. The grayling naturally populates watercourses from central-northern Europe to southern Italy; it was introduced also in the region of the Tagus River, Spain, and Scotland.