California’s commercial salmon fishery is in trouble and what remains of the fishery is sustained by hatchery-born Chinook salmon from the Sacramento-San Joaquin River system. Several of the hatcheries that produce these fish now truck juveniles directly to the San Francisco Estuary so the fish don’t have to outmigrate through the Central Valley’s rivers and the Sacramento-San Joaquin Delta. The scientists involved in this project are asking the question: Is it possible to stagger hatchery releases over a longer period of time to increase the odds that at least some fish will enter the sea when there is enough food (krill) for them? The hypothesis is that these fish are currently released in large pulses (over a narrow window of time) and that this practice subjects fish to a sort of lottery in which there may or may not be enough food, exacerbating boom-bust cycles in salmon numbers. To test these ideas, researchers are examining hatchery reports of when and where fish are released to compute average release times, variabilities in release times, and recovery rates of different release groups. These statistics are being used to explore relationships between recovery rate and release timing in relation to ecosystem dynamics. Results will be shared with NOAA Southwest Fisheries Science Center, the Pacific Fisheries Management Council, and hatchery managers.
Match-Mismatch in the Timing of Hatchery Chinook Salmon Releases and Favorable Ocean Conditions