Data and script from: Hatcheries to high seas: climate change connections to salmon marine survival

We investigated variations in the marine survival of Japanese hatchery chum salmon (Oncorhynchus keta) during 25 years of climate change (1998-2023). Japan is the world’s largest hatchery salmon producer, and is located near the global southern distribution limit of chum salmon. Our goal was to identify local and context-specific metrics related to salmon marine survival for use in the adaptive management of hatchery salmon resources. We hypothesized multiple metrics in three categories of stressors: hatchery carryovers, ocean conditions, and predators and competitors. The hatchery carryovers are stressors related to hatchery rearing that affect survival at a different life stage. We collected, processed, and collated large publicly available datasets of metrics into a comprehensive open-access database encompassing the life cycle of Japanese chum salmon, from eggs to adult spawners. Multivariate regression models showed associations between stressor metrics and adult salmon return rate (marine survival) varied by coastal management region, salmon life stage, and seasonal high seas distribution area. Generalized additive models identified a shift to younger age at maturity and egg size decline in all management regions. Our analysis suggested that maternal traits (egg size, fecundity) and quality of fry hatchery salmon (body size at release) are particularly important for survival at later ocean stages. Our results support the hypothesis that whole life-cycle processes from anthropogenic selection in hatcheries to climate-driven changes in coastal predation, inter- and intra-specific high seas competition, and maternal effects during egg maturation at sea are responsible for the observed coastwide decline in survival of Japanese hatchery chum salmon over the past two decades. Our study highlights the need for an experimental approach to hatchery practices, including monitoring and analyses with updated information, leading to effective management decisions and policies for future sustainability and conservation of salmon resources.