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Connectivity, ecological function and climate change


The mission of the California Fish Passage Forum (Forum) is to protect and restore listed anadromous salmonid species, and other aquatic organisms, in California by promoting collaboration among public and private sectors for fish passage improvement projects and programs. This goal is to restore connectivity of freshwater habitats throughout the historic range of anadromous fish.
The Forum supports fish passage barrier removal, which enhances connectivity and restores the natural processes capable of sustaining healthy anadromous fish populations.

Addressing connectivity is a high priority, cost-effective approach to protecting and restoring anadromous fish populations. Improving connectivity can increase habitat diversity and population resilience and thus compensate for the effects of climate change-induced reductions in stream flow and increases in temperature. Removing the right barriers requires an understanding of connectivity within stream networks.

Fisheries Health


Other Benefits

  • The provision of clean air and water

  • Flood control and the protection of property (homes, schools, businesses, roads)

  • Sediment management

  • Native fish and wildlife habitat, including providing passage for all aquatic species (e.g., amphibians and reptiles) throughout their life stages as well as establishment of migration corridors through enhanced connectivity

  • Carbon sequestration

  • Public safety—inadequate crossing structure can affect road condition (e.g., during tropical storm Irene in Vermont 1,240 road crossing structures were damaged or destroyed and 21 miles of Forest Service roads and trails required almost $7 million in repairs)

  • Groundwater benefits

  • Stormwater improvements

  • Urban water reuse

  • Non-point source pollution reduction

  • In-stream flow conditions are maintained or improved

Ecosystem Function


  • Improves floodplain function—Floodplains are critical for maintaining river productivity and biotic diversity. 

  • Improves resilience to climate change—Eliminating the barriers to fish passage and restoring function to California’s coastal river systems results in ecosystems that are more resilient to climate change effects, such as sea-level rise. Opening miles of high quality habitat upstream of a barrier enhances fish resilience to climate change by providing access to cooler refugia as well as ensuring migration corridors are intact.

  • Enhances connectivity—Reconnects fragmented habitats.Without ecosystem connectivity, areas could remain void of species diversity, as new populations cannot move in to mitigate a local extirpation.

  • Improves upstream nutrient quality—Anadromous fish whose movements are impeded upstream contribute less to upstream nutrient quality through carcass deposition.

  • Invasive species deterrent—Healthy watersheds are less likely to become infested with invasive species because naturally functioning ecosystems favor colonization by indigenous species. Invasive species cost the United States millions of dollars annually in lost food production, tourism and trade.

  • Improves access to more and better quality habitats—Fish passage barriers impede fish and other aquatic life from accessing existing higher quality habitats (size, distribution, and connectivity) upstream and freshwater habitat for spawning and juvenile rearing.

    • Influence flow conditions (depth, velocity, turbulence) and hydraulic features (e.g., pools, riffle, eddy).

    • Reduces spawning substrate (e.g., lack of fine sediment).

    • Reduction in vegetated streambanks, which contributes to erosion and reduces shade.

    • Less refugia (e.g., large woody debris; locations to avoid severe floods, increased temperatures, or predators) and juvenile rearing areas.

    • Less foraging area.

    • Loss in habitat diversity and complexity and degradation of habitats (streamflow diversion, increased water temperature, and decreased water quality).

    • Removal of riparian vegetation and reductions in invertebrates alters the food web.

    • Downstream erosion to bed and banks, downstream channel incision.

  • For every stream mile reconnected, there is more than a $500,000 benefit to communities. For every stream mile opened to fish passage, 12 jobs are supported.

  • Every fish passage improvement structure that is completed benefits from a maintenance-free infrastructure that is likely to last 50-100 years. When aging, soon-to-fail infrastructure is replaced with new structures, significant value is added to local economies by increasing the reliability and stability of its transportation infrastructure.  

  • Many existing fish passage structures are at risk of failing. When they fail, an emergency exists, generally in a financially-strapped, rural and remote area, which creates a financial burden on the entity responsible for maintenance. Planning for high priority fish passage barrier removal provides the needed time for managers to efficiently plan and budget for replacement structures, versus having to replace the structures in crisis mode (which generally costs more).

  • Replacement of fish passage barriers with new designs developed using stream simulation technology results in significant cost savings and limited up-front investments.

  • Fish passage improvement efforts help our society modernize in a way that simultaneously improves transportation and the health and sustainability of our natural resources.

  • Watershed restoration projects generate an estimated 17 jobs for every $1 million invested, through job creation, reduced maintenance costs, and increased ecotourism and recreation.
    • Healthy watersheds increase property values.
    • Reduced costs for repairs and maintenance during the life cycle of an adequately designed structure.
    • Reduced costs for supplying and treating drinking water.


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