The East Australian Current transports tropical fish larvae from the Great Barrier Reef in Queensland to the NSW coastline throughout summer.

Whilst water temperatures remain warm, these larvae develop into juvenile tropical fish that become part of NSW fish communities in rocky reefs as far south as the NSW/VIC border. When water temperatures decline during winter, these tropical fish die-out.

However anticipated water temperature increases due to climate change are likely to lead to greater rates of over-winter survival and establishment of tropical fish populations along the NSW coast.

Already the Tasman Sea, off the east coast of Australia, has warmed approximately 2°C over the past 100 years. Modelling of future water temperatures suggests the Tasman Sea will continue to warm at a rate greater than most other oceans in the world, and this is likely to assist tropical fish to establish viable populations along the NSW coast. Increases in abundance and diversity of tropical fish may have significant impacts on local-temperate marine communities through competition for resources such as habitat and food. The first part of this project will involve dive surveys in reefs and estuaries along the NSW coast to determine the habitats tropical fish use, and identify potential impacts these fish may have in these systems.

In an attempt to determine the increases in water temperatures required for tropical fish to begin surviving over winter and reproducing in NSW waters, impacts of water temperature on the biology and ecology of tropical fish will be explored by comparing fish from latitudes with different water temperatures, as well as using water temperature manipulation experiments at the Sydney Institute of Marine Science.

The research by Hayden Beck of University of Technology Sydney, a 2011 SIMS Doctoral Fellow, will inform the debate on the biological significance of climate change to SE Australia.