A comparison of juvenile life histories among selected Snake River steelhead
populationsBrett Bowersox, Timothy Copeland, and Alan Byrne
Idaho Department of Fish and Game
Steelhead in Idaho Present in Snake, Clearwater, and Salmon River drainages
Provide valuable fishery Well documented variation in ocean life history (A vs B run)
High variation in freshwater habitat characteristics
Freshwater life history not extensively studied in Idaho
ESA listed in 1997
ESA Status Assessments Abundance
How many of them are there?
ProductivityHow well do they
reproduce & survive? Spatial structure
Where are they? Diversity
What are they like?
Technical Recovery Team Efforts No population specific
data Used aggregate A-run, B-
run data for adults at Lower Granite Dam Divided abundance to
population within run-type Assumed all had same run-
type productivity Limited information on life
history or spatial structure
Objectives Compare/contrast freshwater life history data
Examine implications for population productivity
East Fork Potlatch River
Crooked Fork Creek
Fish Creek
Rapid River
Big Bear Creek
Study Populations
Little Salmon(A-run)
Technical Recovery Team Populations
Lower Clearwater
(A-run)Lochsa(B-run)
Environmental Variation
Stream Elevation (ft)
Annual Precipitatio
n (in)Geology Land use
Big Bear Creek 1200-4983 22-30 Loess/
volcanic ash Agriculture
East Fork Potlatch
River2685-4400 22-45 Volcanic
ash/loess Forestry
Fish Creek 2000-6540 30-55 Volcanic ash/granite
Limited Forestry
Crooked Fork Creek 3442-6340 35-55 Volcanic
ash/granite Forestry
Rapid River 2100-8660 14-30 Colluvium/basalt Wilderness
Methods Use 2008 emigrant data from screw traps
Abundance, scale samples, PIT tags Metrics
Emigrant abundance Timing from natal stream Age composition Length at age Detections in Snake/Columbia hydrosystem
Objective 1 Compare/contrast freshwater life history
data
2008 Abundance EstimatesStream Spring Summer FallBig Bear
Creek 3,492 1,245 670
East Fork Potlatch River 1,912 2,706 3,749
Fish Creek 751 3,236 11,960
Crooked Fork 63,679 37,879 3,431
Rapid River 2,380 1,121 1,664
SpringSummerFall
Seasonal Outmigration Variability
Crooked Fork
Fish Creek
Rapid River
East Fork Potlatch River
Big Bear Creek
Age Distribution
Rapid RiverCrooked Fork
Fish Creek
Big Bear Creek
East Fork Potlatch River
Age -0Age -1Age -2Age -3Age -4
Length at Age
1 2 3 40.02.04.06.08.0
10.012.014.016.018.020.0
Spring Migration
BBCCFKEFPFHCRPR
Age
Leng
th (c
m)
Detection rates in Hydrosystem
Stream Spring tags Summer tags Fall tags
Big Bear Creek 0.54 0.16 0.13
East Fork Potlatch River 0.27 0.20 0.16
Fish Creek 0.40 0.35 0.43
Crooked Fork Creek 0.62 0.41 0.55
Rapid River 0.54 0.04 0.33• Spring tags detected in year of tagging (Sp 2008)• Summer and fall tags detected year after tagging (Sp 2009)
Objective 1 Summary A variety of life history strategies
observed between the populations Juvenile rearing completed within natal
streams and downstream reaches Lower elevation populations have
younger age structure than high elevation
Objective 2 Examine implications for population
productivity
Relative Productivity Model
Use abundance, age structure, & assumed survival to estimate initial fry abundance
Use abundance & apparent migration survival to LGD to estimate smolt production
Productivity measure is smolts per fry
Fry to Smolt SurvivalNatal Stream Annual Survival
Stream S = 0.5 S = 0.33
Big Bear Creek 0.138 (1.00) 0.066 (1.00)
EFK Potlatch River 0.083 (0.60) 0.045 (0.68)
Fish Creek 0.106 (0.77) 0.042 (0.63)
Crooked Fork 0.074 (0.54) 0.019 (0.29)
Rapid River 0.058 (0.42) 0.017 (0.26)
• Survival Relative to Big Bear Creek in parentheses
Objective 2 Summary Productivity differences within Technical
Recovery Team populations (Fish Cr v. Crooked Fk / Big Bear v. EFK Potlatch)
Decreasing natal stream survival increases relative advantage of Big Bear & EFK Potlatch
B-run populations need increased smolt-adult survival & fecundities to make up for older age structure
Summary Variation in freshwater life history
important to population stability Low elevation populations very resilient
Results similar to genetic & parr density studies
High “value” of habitat restoration projects for lower elevation populations
Further investigations of high elevation & Salmon River populations
Questions