1. Bryce Glaser Dan Rawding (WDFW)
An Approach for Developing Biological Reference Points for Steelhead Populations in the Lower Columbia Region
Bryce Glaser
Dan Rawding
(WDFW)

2. Biological Reference Points (BRP) ≠ Escapement Goals
BRP are quantitative
Spawners at Maximum Sustainable Yield (MSY)
Spawners needed to seed habitat
Based on current data not on future expectations
Escapement goals are from policy-technical interaction and ideally are based on fish management philosophy
should include quantitative analysis
risk to persistence
fishery stability or maximization of catch
uncertainty

3. Overview Background/Available Data Approach & Analysis
Initial Results/ Model Performance
Development of BRP
Escapement Goals for LCR Steelhead
Summary/Implications
Questions

4. Lower Columbia Region (LCR)
Four summer and fourteen winter steelhead populations in Washington
Iteroparous with repeat spawner rate of 5% to 15%
Hatchery releases beginning in 1950’s with Mitchell Act program
Different populations have different levels of hatchery influence and broodstock types

5. Hatcheries Hatchery program
Chambers Cr winters (Puget Sound origin)
Skamania summers (Washougal origin)
Local broodstocks (Cowlitz, Kalama, Abernathy)
Relative Reproductive Success (RRS) to smolt stage
Chambers (6%) measured in Forks Creek,
Skamania (30-35%)Kalama & Clackamas River,
Wild Broodstock (>80% -adult stage Hood & Kalama)

6. Harvest Mainstem Columbia River - Mixed Stock Fisheries
commercial fisheries- managed for < 2% incidental catch
Stock composition of steelhead catch in both commercial and Treaty fisheries (above BON) is unknown
Sport fisheries have been operated under wild steelhead release since 1984

7. Mark/Re-sight via Snorkeling
Adult Trapping
Redd Surveys
Juvenile Trapping

8. Smolt Trapping with concurrent Adult Escapement data

9. LCR Steelhead Challenges
Short data series and high measurement error for redd counts (coefficient of variation ~ 30%)
Standard salmon spawner to adult recruit relationships do not account for iteroparity
Ocean survival has varied over 10-fold in the LCR introducing much variation in adult recruits
Different proportions of hatchery spawners with limited measurements of RRS

10. Approach
Standardized spawners into wild equivalents using appropriate RRS estimates to discount hatchery spawners to the smolt stage
Standardized SR data into fish density (fish per square kilometer of drainage area)
Developed spawner to smolt relationships to reduce environmental variation caused by 10-fold changes in marine survival and lack of mainstem Columbia River catch estimates by stock
Autocorrelation is not an issue using spawner and smolts
Hierarchical modeling (meta-analysis) using different spawner-smolt-relationships (SRR)

11. Hierarchical Modeling
Borrow strength from other curves - from those with more data
Estimates shrink towards the mean, which yields improved precision of individual BRP
Compromise between individual and fully pooled estimates
Reduces overfitting of individual curves
Allows individual curves to be fit in cases, where there are few data points, outliers, etc.

12. Common set of steelhead spawner to smolt relationships
Spawner to smolt functions come from a random sample of S/R distributions that can be hierarchically modeled.

13. Analysis
Barrowman, N.J., R.A. Meyers, R. Hilborn, D.G. Kehler, and C.A. Field. The variability among populations of coho salmon in maximum reproductive rate and depensation. Ecological Applications 2003: (used km available)
Smolts and spawners per sq. km of drainage area, with spawners adjusted for RRS data
Bayesian hierarchical analysis using WinBUGS with Lognomal error
Vague priors similar to Barrowman so the results are data driven not prior driven
Checked convergence with Brooks-Gelman-Ruben (BGR) statistics.

14. Smolts per Square Kilometer
Hierarchical BH R HS
Wild Equivalent Spawners per Square Kilometer

15. Results
Deviance Information Criteria (DIC) is a Bayesian analog for Akiake Information Criteria (AIC)
Using DIC for model selection BH and HS models were preferred over Ricker model.
These results are consistent with other analysis for yearling anadromous salmonids, that dome shape models (Ricker) do not fit this life history type well.

16. Model Performance Yellow Line- drainage area only
Fitting a curve with no S/R data
Pink Line – Individual estimate

17. Basin Model w/95%CI Superimposed over PNW Population outside LCR
Smol ts
per Sq km
Wild Equivalent Spawners per Sq. KM

18. Biological Reference Points
B = spawners needed to produce 50% of asymptotic smolt estimate
S* = inflection point in curve, spawners needed to seed habitat
MSP = spawners needed to produce maximum smolt production
K = smolt capacity estimate
Productivity = slope of curve at origin; est. of population resiliency.

19. Smolt Capacity = 43 to 55 smolts per KM^2
Seeding Levels = 0.4 to 1.7
Wild Equiv.Spawners per KM^2
Smolt Capacity = 43 to 55 smolts per KM^2
Productivity = 66 to 137 smolts
per KM^2

20. Historic Escapement Goals
Best professional opinion
US v. Oregon TAC recommended 1000 steelhead spawners for the Wind River.
Application of Boldt Case (Puget Sound & Washington Coast) Potential Parr Production model to LCR
Lucas and Nawa (1985) recommended 1400 steelhead spawners for the Wind River
Hierarchical Modeling Approach
Using BRP - ~500 spawners for the Wind River (using HS model)

21. Summary & Implications
BRP are quantitative
useful in developing Escapement Goals.
Hierarchical Model Approach can provide estimates of BRP even for populations with little or no SR data.
Individual curves are improved when data is available.
Basin model sensitive to RRS and HOS estimates, and when spawners use a low fraction of drainage area (Mill-LCR, NF Scappoose)
Basin model potentially useful outside LCR except very small tributaries (OR coast)
Next Steps – model improvement by incorporating steelhead distribution and/or GIS attributes

22. Summary & Implications
In LCR populations – it appears we have been achieving seeding levels or higher in most years.
In LCR - 12/95 (13%) spawner points < S*
Reassessment of current Escapement Goals for LCR steelhead populations is likely warranted.
If LCR steelhead recovery requires improvement in adult abundance:
increase habitat capacity because we are seeding habitat.
and increase wild stock productivity by decreasing pHOS

23. Acknowledgements Data Multiple funding sources
NOAA through Mitchell Act,
Bonneville Power Administration
WDFW
Data
Asotin – Mark Schuck (WDFW)
OR Coast – Eric Suring (ODFW)
Snow Ck – Randy Cooper (WDFW)
KRT - Coweeman and Kalama
WSPE - Mill, Abernathy, Germany, NF Toutle
Region 5 Fish Mgt - Grays, Cedar, EF Lewis, Wind, & Trout
Many techs and bios who collected 95 spawner and smolt points since 1977.

24. Questions???