The jumble of downed trees, broken branches, rootwads, and streamside vegetation that are found in undisturbed stream environments provide hiding spaces that enable salmon to protect themselves from the full force of rushing water. At the same time, these habitats produce large numbers of the invertebrates that young salmon eat. Most streams are now deficient in woody material and many of the backwater oxbows, wetlands and floodplains have been filled and straightened. Meanwhile, where forests and wetlands have been removed, storm run-off is greater and peak flows are higher. Coho are particularly vulnerable to this double whammy, because the effects are magnified in the smaller streams where they reside.
Efforts are under way to improve the winter habitat situation in many watersheds.
In the longer term, projects are being undertaken that involve digging side channels that will fill during winter floods, planting new trees and fencing livestock away from stream banks. A project that has been underway in the watershed of Oregon's Coquille River since 1988 illustrates the possibilities. Directed by the Coquille Watershed Association, a voluntary group which reflects all major resource users in the valley and which is funded through a variety of state, local, federal and private sources, the project is aimed squarely at improving winter habitat for coho. A creek which had been imprisoned in a culvert has been 'day- lighted' and allowed to flow into an artificially created wetland. Many other culverts which had blocked fish from entering small tributary streams, have been altered to allow salmon to pass through into good habitat areas.