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
