Estimating Steelhead Abundance in a High Sediment Stream: Bridge Creek, Oregon

Ian Tattam

Nick Bouwes

Chris Jordan

Michael Pollock

Outline

1) Why trap steelhead in Bridge Creek?

2) 2009 Methods

3) 2009 Escapement Estimate

4) Spawner Distribution

Why Bridge Creek?

•Large Lower Mainstem John Day tributary

•Suspected presence of hatchery adults

•Tributary-scale restoration efforts

Where’s the redd?

1) 2009 Methods

• Upstream/Downstream Adult Trap– Mark-recapture estimate– Proportion of hatchery strays?

• Operated 4/5/2009 to 5/28/2009

• PIT tag (cheek)

• Caudal punch

Trap

Current

Fish

Fish

There really are steelhead in that muddy water!

3) 2009 Escapement Estimate

• Captures:– Upstream: 126– Downstream: 84– Downstream Recaptures: 23

• Population Estimate: 449 (344 to 625)

• Capture efficiency– Upstream: 28%– Downstream: 19%

3) 2009 Escapement Estimate

• CV: 15.3% for combined wild and hatchery estimate

• Population size underestimated - late trap install

• 19% hatchery - likely an underestimate

Adult Length by Origin

0

10

20

30

40

50

60

<500

500-

550

551-

600

601-

650

651-

700

701-

750

751-

800

801-

850

851-

900

901-

950

Fork Length

Nu

mb

er

Ca

ptu

red

Wild

Hatchery

“A” “B”

4) Spawner Distribution

RKM 12

RKM 26

PIT Detection Sites

Wild: 57%

Hatchery: 19%

Wild: 17%

Hatchery: 0%

Detection of Upstream Migrating Adult Steelhead

Conclusions

• Steelhead are entering and spawning in Bridge Creek over a 3+ month period

• Downstream trap box and seining combined resulted in sufficient recaptures

• Flexible pickets allowed operation in high stream flows / velocities

Conclusions

• Hatchery adults appear to spawn lower in the creek than wild adults

• Low reproductive success for steelhead spawning in RKM 1-9

• Are hatchery adults self-regulating?

AcknowledgementsPermitting: Jeff Neal and Chris James

Construction: Steve Corwin, Mike Jensen, Kelly Stokes, Lonnie Goin, Kirt Cook, Glen Moodenbaugh

Installation: Chris James and Nick Weber

Handling/Tagging: Dan Rawding

Trap Operation: Bryn Fleming