West Fork designed and conducted surveys to quantify prespawning mortality (PSM) in the naturally spawning Cedar River sockeye population. These data were compared to PSM observed at the Cedar River Hatchery. The otoliths were removed from all carcasses and provided designation of hatchery- or natural-origin for each fish.

In 2018, West Fork crews determined that approximately 50% of all female sockeye showed evidence of PSM. The reasons for this high rate are being investigated by personnel from WDFW and USGS.