Striped bass ( Morone saxatilis ) migration timing driven by estuary outflow and sea surface temperature in the San Francisco Bay-Delta, California

The influence of climate on the timing of large-scale animal migrations is a major ecological and resource management concern. Anadromous fish migrations can have broad scale impacts on human communities and marine, aquatic and terrestrial food webs. However, isolating the effects of climate change on the timing of life stage transitions for anadromous fish species is challenging. Striped bass ( Morone saxatilis ) exhibit striking variation in migration patterns within their natural range, including migratory behaviors that change with latitude, and climate-induced temperature changes are predicted to drive future habitat and distribution changes. Here we explore the linkages between migration and multiple components of coastal and inland aquatic ecosystems impacted by climate change. By leveraging environmental and fisheries monitoring which began in 1969, we describe the upstream migration timing of non-native adult Striped bass influenced by estuary outflow and sea surface temperature in the San Francisco Bay-Delta, California. Striped bass migrated later in years when Delta outflow was greater and sea surface temperature was cooler. It is likely that temperature thresholds in the ocean during the springtime provide a cue for Striped bass to initiate migration, but sea surface temperature may also represent composite climatic trends influencing Striped bass. Further, the observed variation in migration timing of adult Striped bass has implications for predation risk on the seaward-migration of juvenile Chinook salmon.