Rivers and slow rivers
What is a river?
Rivers include what are referred to as slow-moving waters, where the flow is calm, not very fast and generally tends to slow down even more on approaching the mouths of rivers. This distinction from streams and torrents is arbitrary but allows waterways to be classified into two families, characterised by very different hydrologic and biological conditions.
What fauna and flora?
While the vegetation regularly swept along by floods has trouble developing in the minor bed of the river, the major bed houses abundant plant life, in alluvial soil rich in minerals and water.
Due to the broad range of conditions of rivers, a large variety of fish with adapted forms and behaviours can be found there. For example, depending on whether they live close to the lake bed, in deep water or close to the surface, fish will point their mouths towards the bottom like stingrays and catfish, towards the front like cichlidae and crocodile fish, or upwards like the Arowana or giant Gourami.
Rivers are also travelled by species of migratory fish, who don’t live there but come there to breed, and will join the fast-moving waterways upstream, like salmon, or downstream water, like the eel.