"When we decide which rivers warrant restoration, we need to look beyond what we see with the naked eye. This is because a river that may at first appear healthy and postcard perfect may actually have serious problems. Take a stream in an area that has been logged: there may be alders growing along its banks and blueberries among the forest shrubs. It may look perfectly normal, but unless it has a number of key natural characteristics, it’s not worth much to a salmon.
For one, salmon need rivers with what fisheries biologists call structure: fallen trees and boulders and root wads will do. With these in place, the natural hydraulic force of the river can scour the deep pools salmon need for overwintering.
When a river is restored for the benefit of wild salmon, the benefits of more and bigger salmon reach across the food web. For one, the carcasses of spawned-out salmon get hung up in the roots of old trees along a tangled stream bank and this feeds the river and a long list of species: insects, birds, bears and wolves all rely on the nutrition packed into salmon. When you get salmon you get so much else.”