Over the past decade the expansion of a branching coral in temperate SE Australia has opened the door for a number of new arrivals. Pocillopoa aliciae, a subtropical hard coral, has rapidly expanded over temperate reef “urchin barrens” in the last few years. We have been monitoring these coral beds off the Shelley Beach headland at 8-13m depth and have observed they attract tropical fish species in higher densities than we have previously recorded in our 25 years of surveys in nearby rocky reef habitats. They also support higher densities of temperate fish.
Around 2018 we noted 2 small (~10cm diameter) shallow (2-3m deep) P. aliciae colonies in Cabbage Tree Bay, Sydney and since then have expanded with small coral recruits. . We document the spread and colony growth and their use by a number of coral reef fishes not previously seen in the area.
We will here report on observations of a suite of tropical fish using the coral area. For example, with our recent 2025 surveys 3 species of butterflyfish, a triggerfish a number of other tropical fish spanning a few Families as well as temperate fishes extensively using the corals (feeding, defending, sheltering). Tropicalisation of temperate waters can therefore be enhanced by expanding habitats (in this case, subtropical corals) which can facilitate establishment of coral-reef species otherwise unsuited to local temperate habitats. We estimate, based on these data, how temperate reef fish assemblages may change under future climate change projections.