2011 Preseason adult spring Chinook peak arrival timing and run size prediction for Bonneville Dam

March 23, 2011

The Columbia Basin Research preseason spring Chinook salmon run peak prediction includes mean run timing as well as run size (www.cbr.washington.edu/inseason/adult ). Table 1 shows these results and other related preseason predictions. Figure 1 shows the 2011 predicted size and timing plotted with historical size/timing information using two methods: (A) defining the run as between March 15 and June 15 the predicted run size is 209,000  spring Chinook, (B) defining the run size with a Gaussian arrival distribution and no cutoff dates the predicted run size is 143,600 spring Chinook. Brief details of the preseason predictions are below.

Table 1 Preseason Adult Spring Chinook Run Size Forecasts

Preseason Run Size Forecast Data Run Dates Years Method Source URL
198,400 Upriver Spring Chinook, includes Snake River summer Chinook and is sum of Bonneville Dam counts plus the number of fish of upriver origin landed in lower river fisheries (kept catch plus release mortalities). Forecast for 4 and 5-year olds. January 1 - June 15 Various historical years

U.S. v Oregon Technical Advisory Committee Report

http://wdfw.wa.gov/fishing/crc/2010/crc10dec10_2011_spring_forecasts.pdf

Columbia River Compact, WDFW

Columbia River Compact, WDFW

http://wdfw.wa.gov/fishing/crc/

Columbia River Fisheries, Fish Division, ODFW

http://www.dfw.state.or.us/fish/OSCRP/CRM/

Salmon Preseason Reports, Pacific Fishery Management Council

http://www.pcouncil.org/salmon/stock-assessment-and-fishery-eveluation-safe-documents/preseason-reports/

209,000 Bonneville Dam counts March 15 - June 15 1982-2010 Linear regression last year's adults, jacks, and environmental sensitivity of jacks CBR, Escapement Forecaster Method A Adult Forecasts, Columbia Basin Research, UW

http://www.cbr.washington.edu/inseason/adult

143,600

Median Arrival Day 123 = May 3

Bonneville Dam counts   1982-2010 Linear regression last year's adults, jacks, and environmental sensitivity of jacks, but using "Area Under Curve" counting CBR, Genetic Environmental Model (GEM) Method B (1)

Adult Forecasts, Columbia Basin Research, UW

http://www.cbr.washington.edu/inseason/adult

1. Anderson and Beer. 2009. Oceanic, riverine, and genetic influences on spring Chinook salmon migration timing. Ecological Applications. 19(8):1989-2003.

Figure 1. (A) Historic median arrival day and cumulative counts during counting period Mar 15 and June 15. (B) Peak Arrival Day and estimated spring run as determined by fitting the spring run to a Gaussian distribution. Points are in center of text. Blue-circled 2011 represents the estimated peak timing and total run size based on the two runs size definitions as of March 23, 2011. Details of estimates are given below.

Preseason Run Size Prediction

The preseason adult run size used to be estimated using a linear regression of the previous year's jack run size against adult run size using results since 1982 (1981 for Jacks). However, the relationship has been failing in recent years. Beginning in 2010, an environmental variable is used along with historical count data. Upwelling at 42 degrees North is highly correlated with upwelling across the Northeastern Pacific, and is believed to be an important harbinger of conditions because it is the approximate location of the eastern end of the Sub-Arctic Current that divides to become the California Current and the Alaskan Current. Several other measures of upwelling in various locations and times gave very similar results (not shown). Figure 2 illustrates the regression obtained with run size determined by cutoff dates (Method A):

Adult.count = 37410 + .2479 * Last.Year.Adult.count + 0.0510 * Jack.count*Last.Year.August.Upwelling, r2 = 0.85.

The run size prediction using the Gaussian fits to arrivals (Method B):

Adult.count = 36950 + .1694 * Last.Year.Adult.count + 0.05099 * Jack.count*Last.Year.August.Upwelling, r2 = 0.80.

Figure 2. Relationship of adult counts to previous year's jack counts (spring run only). The 2011 preseason run size prediction based on 2010 data for Method A or Method B (prediction highlighted in blue).

Arrival Distribution and Run Peak

The duration of the spring Chinook run is defined by two methods. Method A, which is used for management of in-river harvest defines a run as the total number of adult spring Chinook salmon passing Bonneville Dam between March 15 and June 15 (date extended to include Snake River destined summer Chinook). Method B, which is a better ecological characterization of the spring run, simultaneously describes the distributions of the spring, summer and fall runs by fitting three superimposed normal distributions to the combined run (Figure 3). The mean arrival date of each normal distribution characterizes the arrival peak independent of the method used to determine run size. Details are available at, "Run timing of adult Chinook salmon passing Bonneville dam on the Columbia River".

Figure 3. Passage counts (thin line) of adult and jack Chinook salmon at Bonneville Dam in 2008 showing the tri-modal pattern. The thick lines depict fitted Gaussian functions for spring, summer and fall runs. The fixed spring run cutoff date is depicted with a vertical red line.

Preseason Run Timing Prediction

The spring Chinook peak run timing prediction (Anderson and Beer. 2009. Oceanic, riverine, and genetic influences on spring Chinook salmon migration timing. Ecological Applications. 19(8):1989-2003.) is based on indices of the run's genetically based run timing plus indices of the ocean and river currents fish encounter on their homeward migration. The genetic run timing basis is inferred from the timing of the previous year's jack run. The effects of ocean currents encountered by both jacks and adults approaching the Columbia River are inferred from the January coastal downwelling indices in the years of their respective returns. The river velocities jack and adults encounter are inferred from river flows in the month prior to their arrivals at Bonneville Dam. The model, calibrated with data between 1978 and 2007, has an r2 = 0.78 (Figure 4).

Figure 4. Spring Chinook predicted arrival date vs. the mean arrival date (1978-2007) from the Gaussian function fit to the "observed" counts.