Preseason adult spring Chinook peak arrival timing and run size prediction for Bonneville Dam, 2009

February 06, 2009

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 2009 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 294,318  spring Chinook, (B) defining the run size with a Gaussian arrival distribution and no cutoff dates the predicted run size is 186,890 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

298,900

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

Age-specific linear regressions of cohort returns in previous run years.

1.

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/salpre.html

294,318

Bonneville Dam counts

March 15 - June 15

1982-2008

Linear regression last year's jacks

CBR, Escapement Forecaster
Method A

Adult Forecasts, Columbia Basin Research, UW

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

186,890

May 3 Median Arrival Day

Bonneville Dam counts

 

1982-2008

Linear regression last year's fit jacks curve.

CBR, Genetic Environmental Model (GEM)
Method B (2.)

Adult Forecasts, Columbia Basin Research, UW

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

1. Joint Columbia River Management Staff. 2009. 2009 Joint Staff Report: Stock Status and Fisheries for Spring Chinook, Summer Chinook, Sockeye, Steelhead, and Other Species, and Miscellaneous Regulations. Online 6 Feb. 2009: http://www.dfw.state.or.us/fish/OSCRP/CRM/reports/09_reports/2009janssjsr.pdf

2. Anderson and Beer. In review Ecological Applications. "Distal, Proximal, and Genetic Influences on spring Chinook salmon migratory timing."

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 2009 represents the estimated peak timing and total run size based on the two runs size definitions as of February 6, 2009. Details of estimates are given below.

Preseason Run Size Prediction

The preseason adult run size is estimated using a linear regression of the previous year's jack run size against adult run size using results since 1982 (1981 for Jacks). Figure 2 illustrates the regression obtained with run size determined by cutoff dates (Method A):

Adult.count = 34351 + 11.82 *Jack.count, r2 = 0.70.

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

 Adult.count = 27952 + 11.60 *Jack.count r2 = 0.72.

Figure 2. Regression of adult counts on previous year's jack counts (spring run only). The 2009 preseason run size prediction based on the number of jacks observed in 2008 for Method A or estimated in 2008 for Method B (prediction highlighted in green).

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 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). A manuscript detailing the run timing model is in review (Anderson and Beer. In review Ecological Applications. "Distal, Proximal, and Genetic Influences on spring Chinook salmon migratory timing.").

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