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)

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

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

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

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)

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

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

Smolt Trapping with concurrent Adult Escapement data

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

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)

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.

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.

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 2003:784-793. (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.

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

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.

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

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

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.

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

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)

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

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

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.

Questions???