Three stocks, all from the Columbia River system (Upriver Brights, Spring Creek, and Lyons Ferry), are assessed pre-spawning mortality (also called "Inter-Dam Losses"). All other stocks have 100% survival between the terminal fishing area and the spawning grounds. Pre-spawning mortality is applied to the total adult escapement as follows:

Spawners(s) = AdltEsc(s)PreSpSurvRt(s) [4.4]

where

• Spawners(s) = number of spawners for stock s
• AdltEsc(s) = adult escapement for stock s
• PreSpSurvRt(s) = pre-spawner survival rate for stock s.