New poleward observations of 30 tropical reef fishes in temperate southeastern Australia

A major outcome of climate change is the poleward shift of species ranges. We use a long-term (16-year) monitoring program to report new poleward observations of the juvenile stages of 30 tropical reef fishes expatriating to temperate southeastern Australia, a global hotspot for ocean warming. Expatriated juveniles (vagrants) from 10 families and 20 genera were observed for the first time on rocky reefs in southern New South Wales, between 57 and 801km poleward of their previously recorded locations. Vagrants were functionally diverse, ranging from small planktivores (e.g. Dascyllus trimaculatus) through to a large piscivore/invertivore (Epinephelus cyanopodus). Tropical herbivores comprised 20% of vagrant species, with four species (Acanthurus dussumieri, A. lineatus, A. nigrofuscus, A. olivaceus) recognised as grazers of epilithic algae and one species (Naso unicornis) known to feed selectively on macroalgae. Pelagic larval duration (PLD) ranged greatly among vagrant species, with shorter PLDs suggesting sub-tropical breeding populations for some species. As water temperatures continue to increase in southeastern Australia under climate change, the greater supply and survival of tropical vagrants may alter the functioning of temperate reefs in this region.