Fall Chinook Salmon Survival and Supplementation Studies in the Snake River and Lower Snake River Reservoirs, 1997 Annual Report.

Falling Behind: Delayed Growth Explains Life‐History Variation in Snake River Fall Chinook Salmon

“…Furthermore, we determined that best-fit threshold parameters were robust to uncertainty in a number of parameters, including the ATU threshold for emergence, FL at emergence, and overwinter survival. Connor et al (2002) reported observations: 1994-1997and 1999-1997and 1999 [1991][1992][1993][1994][1995][1996][1997][1998][1999] 2.7 ± 0.8 2 .1 ± 0.8 9 .0 ± 6.5 1 1 .2 ± 2.9 5 1 .9 ± 14.6 5 2 .7 ± 23.7 [2000][2001][2002][2003][2004][2005] 11.5 ± 20.8 1 .9 ± 1.1 1 1 .7 ± 21.4 3 .1 ± 1.2…”

“…Acknowledging that some overwinter mortality is bound to occur (i.e., u < 1) means that the proportion of fry that adopt a yearling strategy will always exceed the proportion of yearling migrants that pass Lower Granite Dam 1 year later ( Figure 6). Reliable estimates of u are lacking, but Williams et al (2008) considered values of 0.2-0.8 in their analysis and Muir et al (1999) assumed a value of 0.65. If u is at the lower end of this range, then in some reaches and years the number of fish that overwintered may have been as much as two-to threefold greater than the number that were estimated to have passed Lower Granite Dam ( Figure 6).…”

Survival of Hatchery Subyearling Fall Chinook Salmon in the Free-Flowing Snake River and Lower Snake River Reservoirs, 1998-2001 Summary Report.

“…Fish for release groups were PIT tagged at Lyons Ferry Hatchery each week, using standard techniques (Muir et al 1999). At the hatchery, well water was supplied during tagging and loading for transportation at a near constant temperature averaging 12 o C. Fork lengths of all fish tagged were measured, and about 10% of the fish were weighed.…”

“…Results are based on groups released at Pittsburg Landing and Billy Creek on the freeflowing Snake River in 1995 (6 groups totaling 7,681 fish), 1996 (6 groups totaling 7,155 fish), and 1997 (12 groups totaling 14,952 fish) (Smith et al 1997;Muir et al 1998Muir et al , 1999, and the 1998-2001 release groups at Pittsburg Landing and Billy Creek described above (Table 1). Groups released on 27 June 2001 were omitted from these analyses.…”

“…To overcome this problem, we used subyearling fall chinook salmon raised at Lyons Ferry Hatchery as surrogates for wild fish, ensuring that we could release sufficient fish in each group, even late in the migration season. Starting in 1995, we estimated survival and travel time using subyearling chinook salmon reared at Lyons Ferry Hatchery, PIT tagged at the hatchery, and transported upstream for release in the free-flowing Snake and Clearwater Rivers above Lower Granite Dam (Muir et al 1998(Muir et al , 1999Smith et al 1997). Here we report results from releases of PIT-tagged hatchery subyearling fall chinook salmon over four years (1998)(1999)(2000)(2001) in the Snake River and two years (1998)(1999) in the Clearwater River.…”