Unusual occurrences of fishes in the southern California current system during the warm water period of 2014–2018

Abstract An unusually long period of warm-water temperatures occurred off southern California (USA) in 2014–2018, and the highest sea-surface temperature ever recorded in a 103-year span of continuous data collection occurred in August 2018. Poleward distributional shifts in the geographic range of hundreds of marine organisms worldwide have been documented during or just after this and similar anomalously warm periods. We report on the unusual occurrences of 36 fish species (most initially reported by citizen scientists) recorded from the Southern California Current System (SCCS) during this recent period. In combination with previous literature, a remarkable 14 species are reported in the SCCS for the first time. The number of species and families represented is comparable to the number recorded during the 1997–1998 El Nino, widely regarded as the most impactful warming event for this area in the past century.