Limiting Factors



Columbia Plateau Province

Snake Lower Subbasin

SUMMER STEELHEAD
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
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.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass four to eight dams during migration.
Toxic Contaminants Water; Biota -- Pollution and Contamination Pollution: Biological Wastes, Fertilizer, & Pharmaceuticals All Contaminant inputs from upstream land-use activities are often trapped in the reservoirs behind the dams.
Water Quality Temperature -- Water Management Water: Temperature and Gas alteration All High temperatures during upstream migration of salmonids limit productivity.
Water Quantity Altered Flow Timing -- Dam or Hydropower Facility Management Water: Storage or Withdrawal, Channelization, Management Juveniles, adults Frequent water level fluctuations have a deleterious and sometimes fatal effect on juvenile salmoinds. Fluctuations in flows can delay adult salmonid migrations. Modification of the historic hydrograph due to dam operations can result in peak flows that do not coincide with optimal spawning temperatures and can result in year-class failures.