Fish Passage Research

Location: West Coast, USA
Clients and Partners: Humboldt State University and National Marine Fisheries Service (NMFS)

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MLA has long partnered with Humboldt State University (HSU) Environmental Resources Engineering Department to further the state of knowledge concerning fish passage engineering. From 1999 to 2004, MLA worked with HSU and NMFS to evaluate the effectiveness of then-current California fish passage design criteria, and to assist in revising the criteria to improve passage performance and better protect ESA listed salmonids. The findings from three years of field research were presented in the 2004 publication, Improving Stream Crossings for Fish Passage: Final Report.

More recently, MLA and HSU collaborated with NMFS to investigate the implications of regional hydrologic variations on salmonid migration at fish passage facilities. The study examined fish passage opportunities and migrational delay resulting from use of differing statutory passage design flow criteria as well as use of alternative criteria. The study regions were composed of coastal Southern California, coastal Northern California, and coastal Oregon. The study found that applying the same passage design flow criteria to all regions resulted in substantially less passage opportunity for ESA endangered steelhead in evaluated Southern California streams. Findings are presented in the 2014 publication, Comparing Fish Passage Opportunity using Different Fish Passage Design Flow Criteria in Three West Coast Climate Zones. These findings are expected to be used by NMFS as they consider revisions to current passage flow criteria applied for projects involving fishways and other hydraulic-based fish passage designs in the Southern California region.