Limiting Factors



Columbia Gorge Province

Columbia Gorge Subbasin 378

CHUM
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management; Urbanization; Artificial Propagation Migration Impediments Adults Chum have a low propensity to ascend the fishways at Bonneville Dam. Transportation corridors and/or hatchery weirs block chum access to tributary habitats.
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 Morphological Changes Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Fry, adult spawners Mainstem spawning and rearing habitat has been lost due to inundation by Bonneville Dam.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation Eggs, fry, adult spawners Historic chum spawning, incubation, and rearing areas in low gradient streams and rivers have been lost due to urban, industrial, and agricultural development.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Diking; Filling; Riparian Degradation Juveniles, adults Recruitment of large woody debris to lower reaches of tributaries and nearshore areas of the mainstem has been reduced.
Sediment Conditions Increased Sediment Quantity Freshwater-Instream Agricultural Practices Sediment: Bank Destabilization Eggs, fry, adult spawners Sedimentation impacts spawning and rearing habitats used by chum in tributaries and nearshore areas of the mainstem.
Water Quantity Decreased Water Quantity -- Dam or Hydropower Facility Management Water: Storage or Withdrawal, Channelization, Management Eggs, fry Operations provide for intermittent dewatering of spawning gravels used by chum and changes to seasonal and longer-term recruitment of spawning gravels.
PACIFIC LAMPREY
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Juveniles, adults Passage measures developed for salmon do not necessarily provide optimum benefits to lampreys.
Habitat Quantity and Quality Access and Availability; Morphological Changes Estuary Agricultural Practices; Urbanization Diking; Filling; Riparian Degradation; Wetland Loss Juveniles Historical complex habitats have been modified through channelization, diking, development and other practices.
Toxic Contaminants Water; Biota -- Pollution and Contamination Pollution: Biological Wastes, Fertilizer, & Pharmaceuticals Juveniles Contaminants may affect survival and growth of lamprey.
Water Quantity Decreased Water Quantity; Increased Water Quantity -- Dam or Hydropower Facility Management Water: Storage or Withdrawal, Channelization, Management Juveniles, adults Frequent pool elevation fluctuations impact ability of juvenile lamprey to use nearshore substrates for long periods of time.
WHITE STURGEON
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Adult spawners Mainstem spawning habitat has been lost due to inundation by Bonneville Dam.
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Adults White sturgeon are unable to use fish ladders at Columbia River dams.
Instantaneous Mortality Anthropogenic Mortality -- Fishery Management Harvest Adults Sport and commercial harvest limit adult white sturgeon abundance.
Toxic Contaminants Water; Biota -- Pollution and Contamination Pollution: Biological Wastes, Fertilizer, & Pharmaceuticals Eggs, adults Contaminants may reduce adhesiveness of eggs. Contaminants also may affect survival, growth, and reproductive potential of white sturgeon adults.
Water Quality Temperature -- Water Management Water: Temperature and Gas alteration Eggs Elevated water temperature affects white sturgeon eggs.
Water Quantity Altered Flow Timing -- Dam or Hydropower Facility Management Water: Storage or Withdrawal, Channelization, Management Adult spawners Altered flows create suboptimal spawning conditions for white sturgeon.