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Biological Prioritization of Barriers

Caltrans coordinates with California Department of Fish and Wildlife (CDFW), National Marine Fisheries Service (NMFS) and other partners to prioritize locations based on biological significance:

  • Presence or historic presence

  • Diversity of anadromous species

  • Suitable upstream habitat (quality and quantity)

  • Thermal refugia (cool water)

  • Knowledge of expert and local professionals

Prioritizing based on this suite of factors facilitates wildlife connectivity when barriers are remediated, which enhances resilience to climate change effects, such as drought, wildfires, sea level rise, increased stream temperatures in lower reaches, and changes in freshwater flow.

FishPACs discuss criteria they will use annually to rank the specific locations in any calendar year, using locations identified in the Passage Assessment Database.


Criteria for Ranking Locations


I. Species Diversity – Presence of salmon and steelhead species.

  • Species diversity relates to salmon and steelhead species currently or historically present in the stream at or above the existing barrier location. Endangered species have the highest value, followed by threatened species.

  • Where identified high biological value locations benefit multiple salmon/steelhead species, the score for both species would be added to the total species diversity.

    • For example, in the event that endangered Coho and threatened steelhead are present, each species would be allocated a score for diversity.

 II. Habitat – Suitable habitat quality and quantity above each crossing.​

  • Excellent – Relatively undeveloped watershed conditions. Habitat features include mature riparian zones with a mix of mature, contiguous native species, frequent pools, riffles, spawning areas, cool summer water temperatures, and adequate in-channel habitat.  Presence of a fish barrier is the watershed’s only limiting factor.   

  • Good – Habitat is fairly intact but human activities have altered the watershed. Habitat features includes mature riparian zones of contiguous native species, frequent pools, riffles and spawning gravels.

  • Fair – Human activities have altered the watershed with the likelihood of continued or increased activities, with apparent deleterious effects to watershed processes and features. Habitat impacts include lack of mature, contiguous riparian zone, presence of non-native species, infrequent pools, sedimentation evident in spawning areas or summer water temperatures that periodically exceed stressful levels for salmonids.

  • Poor – Human activities have drastically altered the watershed with high likelihood of continued or increased activities, with apparent deleterious effects to watershed processes. Habitat impacts include riparian zones absent or severely degraded, little or no pool formation, excessive sedimentation evident in spawning areas, stressful to lethal summer water temperatures common, lack of in-channel habitat, residential/commercial development. 

III. Best Professional Knowledge – Professional, discretionary value for science-based information known to fisheries & engineering subject matter experts. Some examples of potential considerations include;

  • Current salmon or steelhead presence/usage – maintaining access to current fish stocks gets a higher ranking than providing access to historic or likely extirpated habitat areas.

  • Water quality – opportunities may exist to improve designated watershed Total Maximum Daily Loads (TMDL’s), which directly relate to fish habitat improvements such as sedimentation, temperature and beneficial uses for aquatic species.

  • Status and location of additional barriers on the stream – sites with additional barriers can have either a higher or lower ranking depending on current efforts or support by FishPAC members or other barrier owners, (e.g., local, county, non-profit), to remove or remediate their barriers.

  • Identified, designated critical habitat for the recovery of a listed species.

  • Other aquatic or terrestrial species connectivity – Caltrans is required by state law to prioritize locations based on biological value for salmon & steelhead species. When the FishPAC is aware of opportunities to provide connectivity for other threatened, endangered or special status species (e.g., invertebrates, resident fish, amphibians, lamprey, terrestrial species, etc.), FishPAC members should consider those benefits. 


Information provided on the list of all known fish passage barrier locations within the FishPAC area are based on current survey data, available information (i.e., PAD, existing engineering details, known biological surveys, preliminary surveys, etc.), and professional judgment of biologists or local restoration groups familiar with the watershed.




To prioritize locations for fish passage remediation, FishPAC members will rank the existing locations for remediation based on the three criteria noted below.  Ranking for all locations is determined in the same manner so the numerical scores can be merged or combined to rank sites by county or watershed.  Points for one or more species may be added to the ranking for species diversity. Only one selection is to be made for habitat quality/quantity, barrier type, and status and professional knowledge.

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