Factors Affecting Anadromous Fish Habitats in California


Santa Ynez River steelheadMany 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.


(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.