Key Limiting Factor |
Impairment |
Habitat Affected |
Threat Type |
Threat Name |
Life Stage (s) |
Description |
Habitat Quantity and Quality |
Access and Availability |
Freshwater-Instream |
Agricultural Practices; Forest Management; Urbanization; Dam or Hydropower Facility Management |
Migration Impediments |
Juveniles, adults |
Irrigation diversion dams and culverts create fish passage barriers throughout the subbasin. |
Habitat Quantity and Quality |
Access and Availability; Morphological Changes |
Estuary |
Agricultural Practices; Urbanization |
Diking; Filling; Riparian Degradation; Wetland Loss |
Smolts |
Historical complex habitats have been modified through channelization, diking, development and other practices. |
Habitat Quantity and Quality |
Small-Scale Structural Complexity; Morphological Changes |
Freshwater-Instream |
Agricultural Practices; Forest Management; Urbanization |
Riparian Degradation; Bank Destabilization |
Juveniles, adults |
Lack of habitat diversity, lack of prespawn holding areas, and large woody debris. |
Habitat Quantity and Quality |
Small-Scale Structural Complexity; Morphological Changes |
Freshwater-Riparian |
Agricultural Practices; Forest Management; Urbanization |
Riparian Degradation |
Juveniles, adults |
Cattle grazing threatens riparian function and groundwater inputs |
Instantaneous Mortality |
Anthropogenic Mortality |
-- |
Fishery Management |
Harvest |
Adults |
Spring Chinook are subject to fresh water harvest. |
Instantaneous Mortality |
Anthropogenic Mortality |
-- |
Dam or Hydropower Facility Management |
Migration Impediments |
Juveniles |
Juveniles and adults must pass nine mainstem dams during migration. |
Instantaneous Mortality |
Competition; Pathogens |
-- |
Artificial Propagation |
Hatchery Fish Production; Disease Amplification and Transfer |
Juveniles |
Competition, genetic introgression, and disease transmission from hatchery introductions may reduce productivity. |
Instantaneous Mortality |
Predation |
-- |
Dam or Hydropower Facility Management; Species Management |
Predators: Fish; Predators: Avian; Predators: Marine Mammal |
Juveniles |
An increase in populations of indigenous predator fish species, and the immigration of diving birds are limiting survival of juvenile salmonids. Non-native predator fishes are limiting survival of juvenile salmonids. |
Sediment Conditions |
Increased Sediment Quantity |
Freshwater-Instream |
Agricultural Practices; Forest Management; Urbanization |
Impervious Surfaces; Sediment: Bank Destabilization; |
All |
Channel modifications have led to increased lateral erosion that creates large areas of sand and silt substrate. High levels of sedimentation create problems throughout the subbasin. |
Water Quality |
Temperature; Oxygen; Turbidity |
-- |
Agricultural Practices; Forest Management; Urbanization; Dam or Hydropower Facility Management |
Water: Storage or Withdrawal; Water: Temperature and Gas Alteration |
All |
High temperature, low dissolved oxygen, and sedimentation create problems throughout the subbasin. |