Beaver ponds provide important rearing habitat for coho and other juvenile salmonids. Stream systems with extensive beaver ponds and wetlands, accessible to coho, have been recorded to have significantly higher smolt yields than other systems in the basin. Seventy-eight percent of historic wetlands have been impacted or lost. The Stillaguamish watershed historically supported 11,795 hectares of wetlands. The current total wetland area is estimated to be 2,537.
Wetlands provide several functions that directly impact salmonids.
There are several habitat limiting factors negatively affecting salmon and their ecosystems in the Stillaguamish watershed. The major factors are discussed below. In the floodplains of the Stillaguamish, the mainstem Stillaguamish has lost more than 31 percent of its side channel habitat, primarily from the construction of dikes and revetments. The side channels of the North and South Forks have been decreased by about one-third of historic levels. The losses are mainly due to filling, and can be attributed to the combined effects of revetments, agriculture, and railroad and road construction.