wintering coho

* The Singing Falls Stream Restoration Project *

Winter Refuge for Coho

Habitat Restoration A Key To Salmon Recovery

Coho need safe havens during winter

Wild populations of coho salmon are at such low numbers in most areas of Northern California, Oregon, and Washington, that the species has been proposed as threatened under the Endangered Species Act. The recreational and commercial fishing industries, once making multi-millions of dollars from coho fishing, have been severely hurt by the complete restrictions on coho fishing the past few years. Research by the Oregon Department of Fish and Wildlife has shown that one factor limiting salmon survival is the lack of appropriate habitat for coho salmon during the winter. Because this winter habitat is lacking, only 10-20% of the juvenile coho salmon present in streams at the end of summer make it through the rainy season to smolt (migrate to sea) the next spring. Winter habitat is the area in the stream and surrounding area where young coho can escape from the strong water currents and floods of the rainy season. Large trees and branches in the stream, log jams, flooded wetlands, side channels and pools, and beaver ponds all can provide refuge. Without such areas, the young salmon get washed downstream and will not survive. By restoring winter habitat, the survival of young coho salmon can be increased and the corresponding recovery of the adult salmon runs better assured.

A small refugia pool at bank full in the winter

Good habitat is hard to find

Many types of human activities, including forestry, agriculture, and urbanization, have altered the availability of winter habitat for fish. In the past, biologists thought that logs in the stream were obstructing fish passage and had logging companies remove them. Now we know that large logs in the stream as well as streamside trees and their overhanging roots and branches are critical for fish survival. To create pastures and developable land, streams were straightened and rip-rapped (covered by rock to stop erosion), dikes were built, wetlands were ditched and drained, beavers killed, and tide gates installed. Now we know that the stream meanders, oxbows, side channels, beaver ponds, and flooded wetlands are filled with small coho seeking refuge during the winter. As towns and cities grew areas were paved, wetlands filled, run-off channeled into storm drains, and streams straightened and put through culverts. Now we know that these changes have resulted in increased water velocities and the severity of floods. We find too that the culverts have blocked passage of young fish trying to find their way to calmer waters during storms and floods.

Restoration efforts can pay off quickly

Fortunately there are both short term and long-term things that can be done to restore winter habitat. In the short-term, strategically adding complex woody materials (such as old Christmas trees and the trees from tree thinning operations) in areas of existing deep pools, using large logs, rootwads and boulders to create new pools, and building quiet off-channel pools can provide a quick boost in juvenile survival rates. Assuring that the young fish can also avail themselves of existing good habitat--for example making sure the fish can get through tide gates and culverts during the winter to slower- water areas, can also help boost salmon survival. In the long term replanting trees in streamside buffers, fencing areas where livestock are present, allowing beaver to help re-establish pools, and de-channeling some areas to allow the stream to re-establish its meander will create conditions favorable to coho survival. The construction of artificial wetlands and other storm water retention systems will also help improve salmon survival by slowing run-off and reducing the pollutants entering the streams and rivers.

Adapted by Pacific States Marine Fisheries Commission from information provided by Oregon Department of Fish and Wildlife