They do escapement estimates based on spawner surveys. They walk index areas on a schedule counting fish and redds. They extrapolate that to the anadromous zone based on spawner surveys on known numbers of fish in Snow and Salmon creeks. The methodology has been used for decades and is (was anyway) available in technical reports that WDG did. Because the methodology was used in the Boldt Case area I am sure that it was thoroughly reviewed by the Tribes and maybe some outside folks too.