21 



listing and post dam construction effects) averaged about 2,800, about 

 double the counts during the 197S-1979 period. During this period 

 (1980-1990), an egg bank program for Snake River fall Chinook eventually 

 led to the release of fall Chinook at Lyons Ferry Hatchery, and resulted 

 in the counts at Ice Harbor Dam reflecting not only the escapement of 

 naturally spawning fish upstream of this dam but the returns to the 

 upstream hatchery as well. Counts of Snake River fall Chinook passing 

 Ice Harbor Dam during the period 1991 through 1994 averaged about 3,500; 

 about three-fold the average counts during the period 1975-1979 and 

 about 25% above the levels counted during the 1980-1990 period. Counts 

 of fall Chinook passing Ice Harbor Dam during the period 1991-1994 also 

 represent a combined assessment of both natural spawners and returns to 

 the Lyons Ferry Hatchery. 



Part of the brood stock development program for the Snake River egg bank 

 and the continued developcsent of brood stock for Lyons Ferry Hatchery 

 involved taking fish ('mining') immediately upstream of the counting 

 station at Ice Harbor Dam (Table 2; Figure 2). Between 1976 and 1990, 

 from 162 to 1,613 of the Snake River adult returns were "mined" for 

 brood stock. This resulted in the abundance of natural spawners being 

 depressed by annual levels that ranged from 7% to 53% as the run 

 progressed upstream (Table 1; Figures 3, 4, and 5). "Mining" was 

 confined to known hatchery fish from 1991-1993; in 1994, no fish were 

 "mined" at this downstream location. 



Counts of fall Chinook passing Lower Granite Dam have been made since 

 1975 (Table 3). Total counts of fall chinook passing Lower Granite Dam 

 since 1975 have ranged from 575 fish in 1990 (385 adults and 190 jacks) 

 to 2,585 fish in 1986 (784 adults and 1,801 jacks). Abundance of adults 

 during the 1975-1979 period averaged about 640 fish; abundance of adults 

 from 1980-1990 averaged about 620 fish; and, abundance of adults from 

 1991-1994 averaged about 860 fish or almost 40% higher than the earlier 

 periods before Snake River fall chinook were added to the endangered 

 8(>ecies list as a threatened species. 



Coded wire tag technology provided a tool during the early 1980s to 

 identify individual stocks of salmonids. Use of this tool since 1983 in 

 the Snake River has provided estimates of the number of chinook counted 

 past Lower Granite Dam that were hatchery strays (Tables 3 and 4). 

 Subtraction of the number of strays from the total count of fall chinook 

 at Lower Granite Dam has allowed estimation of the numbers and 

 proportions of the escapements that were the progeny of "natural" 

 spawning (non-hatchery spawned fish). Abundance of non-hatchery spawned 

 adult Chinook passing upstream of Lower Granite Dam during the eight- 

 year period 1983-1990 is estimated to average about 330 fish; whereas, 

 abundance of these fish since ESA listing (1991-1994) is estimated to 

 average about 510 fish or about 55% higher than the pre-listing average. 



The effect of downstream brood stock "mining* on the estimates of 

 "natural" spawners passing Lower Granite Dam can be made based upon 

 simple proportions (Table 1). "Natural" escapements, adjusted for 

 downstream brood stock "mining" since 1983, essentially removes the 

 effects of the egg bank program and the Lyons Ferry Hatchery from the 

 Lower Granite Dam count. Abundance of non-hatchery spawned adult 

 Chinook passing upstreaim of Lower Granite Dam during the eight-year 

 period 1983-1990 after adjustment for brood stock "mining" is estimated 

 to average 456 fish; whereas, abundance of these fish since ESA listing 

 (1991-1994) is estimated to average 512 fish, an increase of about 12% 

 over the pre-listing average. This 12% increase reflects the change in 

 abundance of "natural" spawners before and after ESA listing without the 

 confusing effects of the egg bank and hatchery program. Thus, the 

 escapement data, both with and without adiuatment for the confueinq 

 affects of the egg bank and hatchery program, do not euppcrt changing 

 the status of Snake River fall chinook from thraatened to endangered . 



A summary of the total Snake River fall chinook population whether they 

 were spawned in the wild or spawned in a hatchery is provided in Tables 

 5 and 6 and in Figure 6. 



