Breaking Down the Fish Passage Barriers

Why Remove Dams?

Nationwide, the removal of dams has opened up miles of river habitat for special-status migrating fish. Dam removal decisions require careful planning and should be based on a balanced analysis of the pros and cons of both dam retention and dam removal. Dam retention may serve important functions, such as flood control, irrigation, and hydropower generation, while dam removal may provide benefits to rivers, fish, wildlife, and neighboring communities.


To learn more about dam removal, visit American Rivers’ inventory of dam removal projects or the Clearinghouse for Dam Removal Information.

Addressing the Problem of Fish Passage Barriers


To identify potential fish passage projects for implementation, we need to determine where fish passage impediments exist and what fish passage improvement projects are already in motion. Our major publications summarize existing barriers to fish passage, potential solutions to fix barriers, and related information.

The 2005 Fish Passage Improvement Report (Bulletin 250) identifies potential fish passage impediments and ongoing activities that address fish passage barriers in California waterways.


The 2013 draft report, Technologies for Passing Fish at Large Dams, helps readers understand and evaluate a variety of fish passage solutions. The report describes problems with dams, fish passage technologies, as well as, provides fish passage case studies, and concludes with an examination of fish passage in California. The report is divided into four sections: Problems with Dams, Fish Passage Technologies, Fish Passage Case Studies, and Conclusions.

Fish Passage in the Calaveras River Watershed

The Calaveras River, located in Calaveras and San Joaquin counties, is in the range of historical and essential fish habitat for fall-run Chinook salmon and part of the historical distribution for the Central Valley steelhead. In 1963, completion of the New Hogan Dam blocked all access to spawning habitat upstream of the dam. Downstream of the dam, anadromous fish currently have access to spawning habitat when flows permit. However, migration is hindered by potential barriers including: low-flow road crossings, bridges, dams, and other structures.


The 2007 Calaveras River Fish Migration Barriers Assessment Report provides an inventory and evaluation of potential barriers downstream of New Hogan Dam on the Calaveras River, the Mormon Slough flood control channel, and the Stockton Diverting Canal in Calaveras, Stanislaus, and San Joaquin counties. In addition, the report includes possible solutions to aid fish passage at barriers found in the system. Results of the report are used in conjunction with salmon and steelhead life history data to identify and prioritize fish passage projects and guide modification or removal of fish passage barriers in the river system.


Cooperating with us on the development of the report was Stockton East Water District, with assistance from the California Department of Fish and Wildlife, National Marine Fisheries Service, and U.S. Fish and Wildlife Service. The Ecosystem Restoration Program funded the development of the report.

Fish Passage and the Central Valley Flood Protection Plan


In 2012, our program prepared the Central Valley Flood Protection Plan (CVFPP), Volume 5, Attachment 9C, Fish Passage Assessment. The assessment provides a broad overview on fish passage in the Central Valley, an introduction to Central Valley-protected anadromous fish species, and a comprehensive list of fish passage barriers.


Building on our work in Attachment 9C, we prepared the Central Valley Flood System Fish Migration Improvement Opportunities Report (FMIO Report). The FMIO Report contains technical information related to fish migration improvements in the Lower Sacramento River, Upper Sacramento River, Feather River, Upper San Joaquin, and Lower San Joaquin Conservation Planning Areas. These improvements facilitate fish passage at barriers, reduce fish stranding, improve habitat connectivity, and can be integrated into flood system improvement projects. Information in this report supports the CVFPP planning efforts: Conservation Strategy, Regional Flood Management Plans, and the Basin-Wide Feasibility Studies.


Information from the FMIO Report was condensed into the 2017 CVFPP Conservation Strategy in Appendix K. Synthesis of Fish Migration Improvement Opportunities in the Central Valley Flood System (PDF: 600 KB).