Tidal culverts, bridges and tidegates: A summary of a literature review of fish passage in tidal ecosystems

Fish access improvements to estuarine and coastal ecosystems have consistently been identified as one of the most effective investments for protection and recovery of Pacific salmon species. Several species of Pacific salmon are federally listed, including Chinook and chum salmon which are often dependent on estuaries and marine nearshore habitats during early life history. Salmon access estuaries and lower reaches of streams as juveniles and during migration along shorelines, including small streams categorized as too small or ephemeral to support spawning fish. The consequences of delaying or reducing access to streams and estuarine habitat during portions of the tidal cycle due to man-made structures are not well documented or understood. Washington State has an active fish passage barrier correction program, with millions of dollars spent annually on fish passage barrier remediation. Tidal water crossing structures, including culverts, bridges, tidegates and control structures pose a unique problem for assessment and design for fish passage and estuarine habitat connectivity, since the criteria was developed primarily to allow adult salmon to access upstream spawning habitat. Although tidal events may naturally prohibit migration at some periods of the tide, obstructions can further reduce migration periods, particularly for juvenile salmon, due to increased velocities from undersized culverts or water crossing structures. Little is known about to what extent fish behavioral ecology is modified or how to assess the duration and extent of negative effects to fish migration during the tidal cycles. Washington Department of Fish and Wildlife recently partnered with NOAA Fisheries Northwest Fisheries Science Center to develop a comprehensive literature review and data gap analysis to support an evaluation and update of current technical guidance on tidal water crossing structures. This poster will summarize the findings of the literature review and data gap analysis