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

Evaluating Surrogacy of Hatchery Releases for the Performance of Wild Yearling Chinook Salmon from the Snake River Basin

“…However, we found significant differences between survival estimates for wild Chinook salmon and hatchery spring Chinook salmon, indicating that hatchery spring Chinook salmon should not be used as direct surrogates for wild stocks for certain survival measures. In particular, we found that hatchery spring Chinook salmon tended to have higher juvenile survival estimates through the hydrosystem than did wild stocks, a finding that agrees with some previous work (e.g., Zabel and Williams 2002) but not others (e.g., Smith et al 2002). We also found that, despite their higher estimated juvenile survival, hatchery spring Chinook salmon had lower estimates of overall survival (i.e., SAR) than did wild Chinook salmon.…”

“…Analysis of most PIT tag studies focuses on either juvenile in-river survival or SAR (e.g., Muir et al 2001;Smith et al 2002;Schaller et al 2007), while the adult conversion rates used by managers do not typically differentiate between wild and hatchery fish (e.g., NMFS 2008b [appendix]). Nevertheless, current management guidelines call for monitoring the upstream passage survival of returning adults (NMFS 2008a [RPA 52]).…”

“…For some Pacific salmon Oncorhynchus spp., hatchery fish have served as surrogates for status and trend monitoring of wild stocks when their numbers have been depressed (e.g., Muir et al 1996;Smith et al 2002Smith et al , 2003. This role of hatchery fish as surrogates for wild fish is not without controversy, however.…”