Why is tributary habitat important? For salmon and trout, the smaller rivers and streams of a catchment are vital for spawning and juvenile habitat. But it’s not just salmonids that benefit from restoring the habitat of the tributary streams. Coarse fish that live and breed in the main stems need clean gravels to spawn in too. Significantly reducing the amount of silt washing downstream is good for all fish species. Additional benefits include the protection that bankside vegetation and trees give against climate change, droughts and hotter summers: narrower streams lose less water by evaporation.