Limiting Factors



Blue Mountain Province

Imnaha Subbasin 424, 425

BULL TROUT
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 Seasonal barriers such as irrigation diversions in the Big Sheep Creek watershed impede migrations of bull trout. Diversions associated with the Wallowa Valley Improvement Canal have created barriers to migrating bull trout in Big Sheep, Little Sheep, and McCully creeks.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Wetland Loss; Impervious Surfaces (Road Density); Riparian Degradation Juveniles, adults Modification through riprapped banks, dredging, and elimination of off-channel refugia has reduced or eliminated rearing habitat.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Riparian Degradation Juveniles, adults Cultivation, farming, and pasturing have reduced riparian habitat in many tributaries, especially in the Big Sheep Creek watershed.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices Riparian Degradation; Bank Destabilization Juveniles, adults Channels have attained unsuitable width:depth ratios, which create a shallow and wide system.
Sediment Conditions Increased Sediment Quantity Freshwater-Instream Agricultural Practices; Forest Management Sediment: Bank Destabilization; All Increased sediment is a key attribute limiting bull trout production
Water Quality Temperature -- Agricultural Practices; Forest Management Riparian Degradation All High water temperature is a key attribute limiting bull trout production
Water Quantity Decreased Water Quantity -- Dam or Hydropower Facility Management Water: Storage or Withdrawal Eggs, adults Reduction of flows by irrigation deiversions limits spawning and incubation in Big Sheep Creek.
FALL CHINOOK
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.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Erosion Control; Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation Juveniles In areas modified through riprapped banks, dredging, and elimination of off-channel refugia the diversity of overwintering habitat has been reduced or eliminated.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Diking; Filling; Riparian Degradation Juveniles Cultivation, farming, and pasturing have reduced riparian habitat in many tributaries. Poor riparian condition throughout the subbasin limits Chinook productivity.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices; Forest Management Diking; Filling; Wood/Structure Removal; Wetland Loss Juveniles, Pre-spawn adults Pre-spawning Chinook are impacted by losses of habitat diversity and streambed instability in the lower reaches of the Imnaha.
Instantaneous Mortality Anthropogenic Mortality -- Fishery Management Harvest Adults Fall Chinook are subject to both ocean and freshwater harvest.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass eight mainstem dams during migration.
Water Quality Temperature -- Agricultural Practices Riparian Degradation Eggs, juveniles High temperatures affect the productivity of Chinook in the Lower Imnaha.
SPRING CHINOOK
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.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation; Wetland Loss Juveniles In areas modified through riprapped banks, dredging, and elimination of off-channel refugia the diversity of overwintering habitat has been reduced or eliminated.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Diking; Filling; Riparian Degradation Juveniles Cultivation, farming, and pasturing have reduced riparian habitat in many tributaries. Poor riparian condition throughout the subbasin limits Chinook productivity.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices; Forest Management Diking; Filling; Wood/Structure Removal All Pre-spawning Chinook are impacted by losses of habitat diversity and streambed instability in the middle and lower reaches of the Imnaha. Insufficient substrate size in the Middle and Upper Imnaha limits Chinook spawning and incubation success.
Instantaneous Mortality Anthropogenic Mortality -- Fishery Management Harvest Adults Spring Chinook are primarily subject to freshwater harvest.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass eight mainstem dams during migration.
Water Quality Turbidity; Temperature -- Agricultural Practices; Forest Management Diking; Filling; Riparian Degradation; Bank Destabilization Eggs, juveniles High temperatures affect the productivity of spring/summer Chinook in the Lower Imnaha. Summer temperatures and sediment loads in Big Sheep Creek impede migration of spring/summer Chinook.
Water Quantity Decreased Water Quantity -- Dam or Hydropower Facility Management Water: Storage or Withdrawal Adults Low summer flows, exacerbated by irrigation diversions, impede migration of spring/summer Chinook into Big Sheep Creek.
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.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation; Wetland Loss Juveniles In areas modified through riprapped banks, dredging, and elimination of off-channel refugia the diversity of overwintering habitat has been reduced or eliminated.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Diking; Filling; Riparian Degradation Juveniles Cultivation, farming, and pasturing have reduced riparian habitat in many tributaries. Poor riparian condition throughout the subbasin limits steelhead productivity.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices; Forest Management Diking; Filling; Wood/Structure Removal; Wetland Loss Juveniles Lack of diverse, deep, and cool habitat types in the Big Sheep Creek and Little Sheep Creek watersheds limit steelhead fry colonization and summer rearing.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass eight mainstem dams during migration.
Water Quality Turbidity; Temperature -- Agricultural Practices; Forest Management Diking; Filling;+E64 Riparian Degradation; Bank Destabilization Eggs, juveniles Summer temperatures and sediment loads in Big Sheep Creek limit steelhead.
Water Quantity Increased Water Quantity -- Forest Management Water: Runoff Coefficient Alteration All Frequent high flow events in the Big Sheep Creek and Little Sheep Creek watersheds resulting from modification of upland vegetation through timber harvest and fires have changed spawning substrate availability and disrupt steelhead incubation.