Site H: Healthy Salmon Habitat

These pictures were taken on  a recently rebuilt bridge, formerly used by the owners of the dairy farm that existed before TWU acquired the land. This is an area of ideal salmon habitat. Note the gravel and small rocks in the stream. This is the type of substrate salmon need to lay their eggs in. The many branches and logs in the stream are also very important. They slow the water, decreasing the amount of silt and making it easier for the fish to swim. They also create eddies where the fish can rest and spot food from.

The many trees over the water are also very important. Although we may like our water warm, the fish like it cold. Not only does warm water overheat the fish, but it also can’t hold as much oxygen, so fish can not breathe as well, if at all. The trees provide shade for the water, keeping it cool. Their strong roots also hold the soil in place, keeping the water from getting too silty – remember that to a fish, silty water is like us trying to live in a sandstorm. Their gills get damaged and they get dirt in their digestive tract. Finally, the trees also provide homes for many insects and other invertebrates. These provide food for the fish when they fall into the water.

As we think about heat, it is also important to remember that the older a forest is, the cooler it is in the summer, and the warmer it is in the winter. This is because as a forest gets older, more evergreen trees grow relative to the number of deciduous trees. Evergreen trees provide more shade in the summer, and trap the heat better in the winter. So you can see why the salmon do much better in older-growth areas: cooler water in the summer, and less ice in the winter. See if you can notice the changes in warmth as you walk along the trail.