A tributary is a small stream that feeds into a larger one. For example, the Fraser River has thousands of tributaries. The largest tributaries to the Lower Fraser River are Chilliwack River, Harrison River, Pitt River and Stave River. The Squamish River also has many tributaries, which include Cheakamus River, Mamquam River, Ashlu Creek.
A watershed is made of a network of tributaries. Water flows from the smallest brooks into creeks, then into streams before roaring into the main stem of the river. Spawning salmon travel up a river and spawning usually takes place in tributaries. The smallest tributaries are usually most vulnerable to habitat destruction, which results in the loss of salmon spawning habitat.
Fishing regulations of a river may differ from one tributary to another, so it is always wise to check them before your fishing trip.