1. Ecologic and Demographic Costs of Releasing Non-migratory Juvenile Hatchery Steelhead

2. Hatchery Production Wells Hatchery Steelhead: 450,000 fish annually
USACOE tagged 240,000 in three consecutive years
broods
Monitored releases to recapture PIT tags by truckload.

3. Natural Production
This is combined data for the Methow and Okanogan populations.

4. Study Objectives
Can a volitional release be used to efficiently segregate migrant and non-migrant fish?
What is the “cost” of releasing non-migrant fish?

6. Wells Hatchery

7. Methods
Release monitoring: Separate estimate of PIT tag rate per truckload
Residual sampling-Twisp River: Captured fish expanded by PIT tag rate
Survival estimates-all releases:
Release to Residual (juvenile)
Release to McNary Dam (juvenile)
Release to Bonneville Dam (adult)
Release to Wells Dam (adult)

8. Twisp River Releases Brood year Volitional migrants Non-migrants
Non-migrants
Truckloads
PIT tags
Total fish
2002 5
25,211
45,180 4
30,813
50,210
2003
24,566
51,220 2
9,401
26,085
2004 6
24,379
52,245 3
10,886
23,310
Total 16
74,156
148,645 9
51,100
99,605

9. Residual sampling Hook and line angling July-August
Recaptured 792 PIT tagged fish
Release type determined for 515 fish

10. Estimated number (% of release type)
Results
Brood
Migration type
Number captured
Estimated number (% of release type) G P
2003
2004
2005
Total
2002
Volitional 21 3 1 25
36 (0.08)
177.5
<0.005
Non-migrant
159
163
269 (0.54) 13 14
29 (0.06)
108.7 34
103 (0.39) 50
122 (0.23)
623.46
229
486 (2.08)
180 53
282
515
1,045

11. Mean % recovered (95% CI) by release type in the Twisp River
Mean of the total recoveries by release type for each brood. Twisp River only.

12. Adult survival
brood PIT tagged fish released by type and subbasin.
Volitional
Non-migrant
Total
Twisp
74,156
51,100
125,256
Chewuch
86,729
13,985
100,714
Methow
99,848
15,510
115,358
Okanogan
109,920
19,402
129,322
370,653
99,997
470,650
Used all releases to calculate adult survival.

13. Mean survival (%; 95% CI) from release to McNary Dam
Cormak Jolly Seber survival estimates calculated by Townsend and Skalski at UW for PUD. Releases in all basins combined by brood and type.

14. Mean SAR (%; 95% CI) from release to Bonneville Dam
3-year mean % survival for all releases. Used Bonneville to eliminate confounding effects of selective fisheries. Vol = 1.18%, NM = .26%

15. Conclusions Volitional releases produce 0.10 residuals per adult
Non-migrant releases produce 1.8 residuals per adult
Properly conducted volitional release from Wells Hatchery would result in:
Not releasing 10% of juvenile steelhead population (i.e., non-migrants)
Non-migrant hatchery steelhead would enhance or replace some rainbow trout production
Wells Hatchery would produce 3.1% fewer adult returns to Wells Dam
Would not adversely impact recreational fisheries
Assist in reducing pHOS
Reduce residualism in the natural environment by 35.7%.
Reduction in competition would increase juvenile survival

16. Questions?