Assessment of Fishes, Habitats, and Fish Passage at Tide Gates on Deer Island Slough and lower Tide Creek. Project Report, 2009

摘要

Multiple factors have contributed to the decline of anadromous salmonids throughout the Columbia River basin. Currently, there are 13 evolutionary significant units of salmonids listed under the Endangered Species Act (ESA) that migrate through the Columbia River. The lower Columbia River and estuary are of particular importance because all stocks of anadromous salmonids within the basin use the area to varying extents, especially as rearing and foraging habitat for juveniles (Bottom et al. 2005). Lower Columbia River habitats have been substantially altered by flow manipulation and reduced connectivity between the main channel, floodplains, and tidal wetlands. The construction of dikes, tide-gated culverts, and the filling of tidal wetlands has resulted in a 65% reduction of tidal marshes and swamps compared to that historically present (Bottom et al. 2005). Restoring or improving the connectivity between tidally-influenced side channel habitats and wetlands to improve conditions for juvenile anadromous salmonids has been included in recovery and management plans and regulatory requirements including the Sub-basin Plan for the Columbia Mainstem and Estuary (Lower Columbia Fish Recovery Board (LCFRB) 2004) and NOAA Fisheries FCRPS Biological Opinion (National Marine Fisheries Service (NMFS) 2004). Tidal wetland restoration is also consistent with the Northwest Power and Conservation Councils biological objectives outlined in the 2000 Columbia Basin Fish and Wildlife Program.