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