Rivers and rapids are the water systems’ “blood vessels”. When water splashes and sprays in whirlpools and eddies, the water oxygenates and the oxygen is carried out into the lakes. The streams also carry with them insects, parts of plants and other things that fish eat. They gather to feed on what the water brings in places such as river mouths.
Flowing waters are also important spawning grounds for grayling and brown trout. Their eggs are well protected between sand and gravel on the bottom, and they are still reached by oxygenated water which is vital for the development of roe and fry.