For example, coho salmon, which spend their first winter in the stream environment, need places where they can escape the high-velocity flood flows associated with winter storms. These are usually old river channels and wetlands in the floodplain, or the upper reaches of streams, where floodwaters are slower than flows in the main river channel during heavy rains. Land Use and Aquatic Habitat Several land use activities affect the landscape in ways that in turn affect salmon habitat or, more generally, aquatic habitat. Virtually anything that affects the quality of water in a stream or wetland can affect aquatic habitat. For example, bare soils washed into streams will eventually settle out, and could cover up gravel beds needed for spawning.
Sediment can suffocate fertilized eggs.
Soils suspended in the water can hurt fish gills and make it difficult for fish to find food. Changes in water temperature can have a major effect on stream life. Salmon prefer water temperatures of 40 to 60 degrees F. Water temperatures over 70 degrees F can make fish more susceptible to disease, and can lead to death. Scientists generally agree that one of the biggest factors influencing stream temperatures is the removal of vegetation, in particular trees, from beside the stream. The riparian area, the upland area next to a stream, has a critical effect on the quality of the habitat in the stream.