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Many anadromous aquatic habitats in the western United States have been highly altered from their historic condition. The habitat changes are the result of multiple natural and human-induced sources and have impacted aquatic species in these systems in many ways. Common factors that adversely impact fish populations in California’s anadromous waters include:

  • changes in runoff patterns and water storage

  • land-use and natural resource extraction activities

  • spatial and temporal changes in connectivity

  • non-native species introductions

  • increased predator populations

  • commercial and recreational fishing

  • hatchery operations

  • natural environmental variations


To address these stressors, many locally-based, site-specific, diverse habitat restoration activities have occurred in California and the greater Pacific Northwest. Recently, regional assessments of restoration needs and prioritization related to anadromous fish and their habitats have occurred throughout the Pacific Northwest. Many of these assessments have ranked connectivity as the top priority for strategic regional restoration*. These projects have generally had the highest likelihood of success, are cost effective, show immediate results, are long lasting, and can guide where other restoration activities should be implemented based on restored access to larger areas of habitat.


In California, several recent documents related to recovery and management of federally and state listed fish species have also made fish passage a high priority, including:


In addition to the anadromous species listed above, the USFWS has completed recovery plans for Shortnose Sucker and lost river sucker populations, and identifies removing fish passage barriers as a primary action to recover both sucker populations. The Forum recognizes that fish passage is an important issue to many aquatic species in anadromous and non-anadromous waters, and  acknowledges the importance of other limiting factors for anadromous fish survival, such as healthy riparian habitat, and water quality and quantity. Many of the Forum Memorandum of Understanding signatories also work to address issues of water quality, quantity, policy and practice modifications, and other forms of in-stream and riparian habitat restoration that will improve the overall anadromous and resident fish populations within the Forum’s region. The Forum recognizes, through its focus on fish passage issues, that without access to freshwater habitat, other anadromous fish restoration efforts will not succeed.

Fish Species Affected by Passage Barriers in California

Anadromous Species


California streams and rivers with access to the ocean were historically home to several native anadromous fish species. These include Chinook salmoncoho salmon, steelhead/rainbow troutcoastal cutthroat troutgreen and white sturgeon,pacific lampreyriver lampreyeulachon, and threespine stickleback. American shad and striped bass are also prevalent non-native anadromous species in many systems.


Historically, anadromous fish passage efforts in California have focused on Chinook salmon, coho salmon, and steelhead. Pink salmon have only occurred rarely in California since the latter half of the 20th century. Chum salmon are slightly more common that pink salmon, but are still highly limited in California. Coastal cutthroat trout are a State of California Species of Special Concern, but have no federal status and have generally not been the focus of fish passage efforts. Passage impacts on green and white sturgeon are almost exclusively limited to large dams and therefore, passage improvement projects for sturgeon are complex, expensive, and not common. Currently, there are efforts across the Pacific Northwest to analyze and mediate the impact of barriers on lampreys. These efforts are often linked to passage projects associated with salmon and steelhead and once refined, will likely consist mainly of additions or alterations to traditional salmonid passage designs. Passage does not likely have a major impact on eulachon as they are found in the lower reaches of coastal rivers and streams and spend very little time in freshwater. Finally, threespine sticklebacks are highly adaptable and show a wide variety of life history strategies that likely greatly reduce the impact of barriers.


Other Species


Beyond anadromous fish species, California has a fairly limited number of species that are federally listed or included in the State Wildlife Action Plan (SWAP) that occur in anadromous waters. Delta smelt are listed as threatened under the federal and California Endangered Species Acts (ESAs). Longfin smelt are listed as threatened under the California ESA but are not listed federally. Both delta and longfin smelt have been subjected to massive changes in their native habitat and environment but passage is not considered an important factor in these species declines.


Shortnose suckers are listed as endangered under the federal and California ESAs. Klamath largescale suckers are included in the SWAP but are not listed under the federal or California ESA. Both of these sucker species are uncommon in the anadromous reach of the Klamath River.


The Forum will continue to focus on fish passage assessment, prioritization, and implementation for salmonids and lamprey. Also, the Forum will consider actions to address other anadromous and resident species in anadromous watersheds as the need arises and cost-effective passage methods are developed.


(1)Hoobyar, P.  2003. Restoration priorities for the Hood and Lower Columbia Basins. Oregon Watershed Enhancement Board Prioritization Framework.

(2) Roni, P., T. J. Beechie, R. E. Bilby, F. E. Leonetti, M. M. Pollock, and G. R. Pess. 2002. A Review of Stream Restoration Techniques and a Hierarchical Strategy for Prioritizing Restoration in Pacific Northwest Watersheds.  North American Journal of Fisheries Management 22(1):1-20.

Graphic on this page is from a report by Dr. Peter Moyle, Dr. Rob Lusardi and Patrick Samual: SOS II: Fish in Hot Water - Status, threats, and solutions for California salmon, steelhead, and trout.

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