Off-Channel Habitat Use By Juvenile Salmonids in the Tidal Freshwater Section of the Lower Columbia River

The Columbia River historically supported one of the most productive populations of salmonids in the world. High quality off-channel habitats provide rearing and refugia opportunities for juvenile salmonids and are particularly important in the lower river and estuary. Habitat loss due to large-scale land conversion, diking and hydrosystem development have reduced the amount and quality of rearing habitat available to juvenile salmon.  Extensive habitat restoration efforts are ongoing in the lower river to improve rearing opportunity for juvenile salmon. However, several uncertainties remain about the benefits of lower river habitats, including how tidal freshwater habitats benefit upriver stocks. The Lower Columbia Estuary Partnership and NOAA have conducted ecological monitoring in the lower river over multiple years, representing the most consistent fish collection record in the tidal freshwater reaches of the lower river to-date. We present data indicating usage of tidal freshwater floodplain and tributary habitats by salmonids belonging to stocks originating from the interior reaches of the Columbia River and discuss the benefits of these habitats for outmigrating salmonids. Our results support the need for continued protection and restoration of lower river habitats.