The Crenon comprises the source region of the river. The Crenon is divided in EuCrenon (sources region) and HypoCrenon
(headstream). Usually no fish live in the Crenon.
The Rhithron is the torrential-like part of the river, here the temperature never rises above 20 degrees Celsius.
The higher part with stronger current is populated only by salmonids like the brown-trout (Salmo trutta fario).
The Rhithron is divided in three parts: Epirhithron, Eurhithron ed Hyporhithron. In the lower part (below the salmonid
zone) it is populated with trout, grayling, barbel and chub. Additionally the pike can also be present.
The Potamal is the lowest part of the river, large and with slow current. The temperature can rise during summer months over 20 degrees Celsius.
Typical fish here are Cyprinids like carp, tench, chub and predators like pike and perch.
