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Upper Willamette River Steelhead
Distribution
UWR steelhead occupy the Willamette River and its tributaries upstream of Willamette
Falls (Figure 34). This is a late-migrating winter group that enters freshwater in March
and April (Howell, Jones et al. 1985). Only the late run was included in the listing of this
species, which is the largest remaining population in the Santiam River system. Table 25
identifies populations within the UWR Steelhead salmon ESU, their abundances, and
hatchery input.
Table 25. UWR Steelhead salmon populations, abundances, and hatchery contributions
(Good, Waples et al. 2005). Note: rpm denotes redds per mile.
Population
Historical
Abundance
Most Recent
Spawner
Abundance
Hatchery
Abundance
Contributions
Mollala Rivers Unknown 0.972 rpm Unknown
North Santiam River Unknown 0.963 rpm Unknown
South Santiam River Unknown 0.917 rpm Unknown
Calapooia River Unknown 1.053 rpm Unknown
Total Unknown 5,819
Life History
Winter steelhead enter the Willamette River beginning in January and February. They do
not ascend to their spawning areas until late March or April (Dimick and Merryfield
1945). Spawning occurs from April to June 1 st and redd counts are conducted in May.
The smolt migration past Willamette Falls also begins in early April and extends through
early June (Howell, Jones et al. 1985) Migration peaks in early- to mid-May. Steelhead
smolts generally migrate away from the shoreline and enter the Columbia via Multnomah
Channel rather than the mouth of the Willamette. Most spend two years in the ocean
before re-entering fresh water to span (Busby, Wainwright et al. 1996). Steelhead in the
UWR DPS generally spawn once or twice. A few fish may spawn three times based on
patterns found in the LCR steelhead DPS. Repeat spawners are predominantly female
and generally account for less than 10% of the total run size (Busby, Wainwright et al.
1996).
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