Brook lamprey (Eudontomyzon mariae,)
It is a very rare, endangered species, with a very important role in the food chain, helping to natural selection by eliminating specimens of weaker or diseased fish.
The Lamprey can be easily recognized mainly by the strange form of the body, resembling a snake rather than a fish. It has a nearly cylindrical body, devoid of finning pairs, and the circular, jaw-free mouth is provided with two very sharp blades with which it cleaves the skin of other fish, sucking their blood. It can reach a maximum length of 30 cm (most of the specimens measure 15-20 cm).
It preferrs areas with smooth waters, muddy or sandy bottom, available in deeper water basins or in ponds created along the river.
The Conservation Status of Lamprey is unfavorable (inadequate), being an extremely rare species for whose protection there have been designated Natura 2000 sites in only 3 EU countries.