Several watershed characteristics – or key ecological attributes (KEAs) as they are called ─ such as habitat complexity, riparian function, water quality, and floodplain connectivity are used to define healthy freshwater and estuarine habitats that are essential to supporting a viable coho population.
Complex stream habitat is particularly important for winter survival of juvenile coastal coho because it provides shelter from predators and high winter flows, which can prematurely flush juveniles downstream. It is also important during summer months when high water temperatures can threaten the fitness and survival of juvenile salmon. Similar conditions support coho survival and productivity during their stay in the estuaries. Habitat conditions that create sufficient complexity for juvenile rearing and overwintering include large wood, pools, connections to side channels and off-channel alcoves, beaver ponds, lakes and wetlands.
These habitats (and the benefits they provide) are maintained through watershed processes that connect them to the surrounding landscape, especially riparian areas, hydrologically connected wetlands, and upland stands of timber that deliver pulses of large wood and gravel. Beavers are particularly important to coho in creating critical off-channel rearing habitats. In addition to creating high quality physical habitats, beaver colonies also drive essential watershed process that sort gravel, filter sediments, and maintain cold water and base flows in summer. Finally, the unimpeded movement of coho between stream reaches and off-channel habitats is essential.