Province Summary


Imnaha Subbasin Summary

The Imnaha subbasin is located in the farthest northeastern corner of Oregon near the center of the Columbia Basin. Like the Grande Ronde, the Imnaha River flows in a northerly direction and is a direct tributary to the Snake River. The entire drainage is contained in U.S. Geological Survey (USGS) 4th field hydrologic unit code (HUC) 17060102 and joins the Snake River at river mile (RM) 191.7, approximately 48 river miles upstream of Lewiston, Idaho, and 3.4 miles upstream of the Salmon River confluence. The headwaters of the Imnaha River drain the eastern escarpment of the Wallowa Mountains and originate within the Eagle Cap Wilderness. At lower elevations, the Imnaha obtains flow from streams draining an adjacent plateau, which is located between the Wallowa River drainage to the west and Hells Canyon of the Snake River to the east. Ninety-eight percent of the subbasin lies within Wallowa County, with the remaining 2% split between Baker and Union counties. The subbasin is sparsely populated and contains only the small town of Imnaha (population 25) within its boundaries.

Source: Imnaha Subbasin Plan

Status and Trends of Focal Species in Imnaha Subbasin
 
Species ESU MPG Population Biological Objective (s) Biological Status Federal Status Data / Charts
Fall Chinook Snake River       Draft Recovery Plan Criteria :
Unknown
Subbasin Plan Objective :
3,000 natural adults290
 
Redd Counts
2009: 36 redds 143
Threatened Status & Trends
Spring Chinook Snake River  Grande Ronde-Imnaha  Imnaha, Big Sheep Creek  Draft Recovery Plan Criteria :
Unknown
Subbasin Plan Objective :
3,800 natural adults (5,740 total returns)290
 
NOSA Estimate
2016: 607 spawners474
Redd Counts
2016: 524 redds (mixed)170
Juvenile Emigrants (natural)
2010: 145,179 juveniles (natural) 172
Threatened Status & Trends
Pacific Lamprey       Subbasin Plan Objective :
None
 
Unknown Species of Concern No Data
Summer Steelhead Snake River  Imnaha  Imnaha  Draft Recovery Plan Criteria :
Unknown
Subbasin Plan Objective :
2,100 natural adults (4,315 toal returns)290
 
Redd Counts
2016: Camp Creek - 40 redds35
Threatened Status & Trends
Bull Trout Imnaha    Imnaha River, Big Sheep Creek, Little Sheep Creek, McCully Creek  Draft Recovery Plan Criteria :
5,000 adults (no delineation among local populations)291
 
Redd Counts
2016: 235 redds141
Threatened Status & Trends
    
View abundance data for Imnaha Subbasin
 
Hatcheries located in Imnaha Subbasin
**Hatchery data will be updated in 2016**

Hatchery / Acclimation Pond Hatchery Info Releases / Returns Program Reviews(APRE / HSRG / HGMP / USFWS) Map
Imnaha Pond View View View View
Irrigon Fish Hatchery View View View View
 
Hatchery Releases and Returns to Imnaha Subbasin358
**Hatchery data will be updated in 2016**

Some releases into subbasins may be from hatcheries located in other provinces and subbasins. Hatchery releases of anadromous fish, within the geographic range of an ESU/DPS, are listed accordingly.
 
Hatchery / Acclimation Pond Species ESU/DPS Released in 2009 Returns to Collection Facility in 2009 Data as of
Imnaha Pond Spring Chinook Snake River Spring/Summer Chinook ESU 234,963 1,160 8 / 30 / 2010
Irrigon Fish Hatchery Rainbow Trout 163,066 8 / 30 / 2010
Summer Steelhead 45,298 8 / 30 / 2010
Lookingglass Fish Hatchery Spring Chinook Snake River Spring/Summer Chinook ESU 58,839 8 / 30 / 2010
Recovery Status for ESA-Listed Salmon and Steelhead in the Imnaha Subbasin146, 177

Updated : 5/27/2010

Species Population Abundance Threshold Mean Abundance Major Spawning Area Growth Rate Recruits / Spawners Current Viability
Summer Steelhead Imnaha River 1,000 Unknown Unknown Unknown Unknown Moderate
Spring/Summer Chinook Imnaha River 750 395 1 of 1 1.05 0.80 Low
  Big Sheep Creek 500 4 ----- Unknown 0.29 Functionally Extirpated
Limiting Factors in the 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.