West Fork Environmental conducted a three year study investigating the spatial and temporal distribution of hatchery and naturally produced sockeye salmon spawning in the Cedar River, Washington. West Fork crews surveyed 21 miles of river weekly during the spawning season to recover, measure and extract otoliths from sockeye carcasses. Adult sockeye recovered during these surveys were marked as fry in the hatchery using a thermal chilling process that leaves unique patterns in the otolith structure allowing determination of brood origin and release site. The study provided Seattle Public Utilities information comparing the naturally spawning population to the Cedar River Hatchery broodstock.