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Aim: Compare the distribution and composition of temperate Labridae (wrasse) assemblages on shallow water coastal reefs in South-Western Australia between 2006 and 2015, after a decade characterized by both gradual ocean warming and severe heatwave events. Location: South-Western Australia from Port Gregory to the Recherché Archipelago. Methods: Surveys of Labridae fishes were conducted in 2006 and repeated in 2015across 112 reefs spanning 2,000 km of coastline, using diver-operated stereo-video systems (stereo-DOVs). We used a hierarchical design with seven regions, four locations in each region, four reef sites in each location and twelve transects in each site. Results:In 2015, we found an increase in abundance of tropical and subtropical labrid species that were rarely observed in 2006. Three temperate species declined in abundance, which tended to be large and slow growing fish. Twenty-two labrid species increased in abundance. There was also a discernible poleward shift in 20 of the 25 most abundant and representative labrid species from 2006 to 2015. The labrid community composition was explained predominantly by sea surface temperature (SST), physical reef structure and kelp (Ecklonia radiata) cover. Main conclusions:Our study reveals that labrid assemblages associated with the shallow water temperate reefs of South-Western Australia have undergone rapid changes across almost 2,000 km of coastline, with warm-temperate waters showing the strongest change. However, cool-temperate waters on the south coast also showed significant changes in the composition of the labrid assemblages. Our findings provide important insights into the effects of warming and habitat loss on warmtemperate assemblages and the potential trajectory of change for cool-temperate assemblages under a warmer future. K E Y W O R D Sassemblage shifts, climate change, endemic fish, Labridae, marine, sea surface temperature, South-Western Australia

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