A unicorn fish.
Tropical fish will reach the south coast of NSW in a matter of decades, posing a grave threat to local fish and native kelp forests.
University of NSW research fellow Erik van Sebille says climate change is dramatically heating the ocean off eastern Australia, prompting tropical fish to migrate south to find waters of suitable warmth.
The oceanographer says unicorn fish, pictured, and surgeon fish, usually found in coral reefs, have been found near Sydney and, if nothing more is done to fight climate change, they will make it to the south coast of NSW.
"It's basically one big musical chairs, where all of the species living along the east coast of Australia have to move southwards to keep in line with their preferred temperature habitat," he said.
"Given how far [tropical fish] have come already in the last 30, 40 years or so, it can't be more than a few decades before they come to Batemans Bay."
Elsewhere tropical fish have devastated underwater kelp forests, leaving behind a "desert of the sea", he says.
Overseas examples show tropical fish are used to eating coral, which is hard to digest, so they eat the nutritious kelp forests quickly, destroying whole ecosystems.
"It might come back after a few years, maybe 10, 20 years, but particularly for the fisheries industry, of course, that's a long time to wait," Dr van Sebille said.
He is working with a team of UNSW biologists and climatologists and will present his research at this week's Greenhouse 2013 conference in Adelaide.
He says the stretch of water between Newcastle, NSW and Tasmania on the east coast of Australia is warming faster than almost anywhere else in the world.
According to the Intergovernmental Panel on Climate Change's latest report, it has warmed 2C over the past century.
Modelling under the ''business as usual'' scenario suggests it will warm up an extra 5C in the next 100 years.
Dr Van Sebille's team is researching how Australian tropical fish interact with kelp forests and how the forests can be made resilient to their threat.
"You want the kelp to have its best possible defence and to be as prepared as possible, so anything that deteriorates the quality of the kelp wouldn't help, anything that overuses the kelp wouldn't help," he said.
If strong action is taken to prevent climate change, warming in the eastern current can be quite limited, Dr van Sebille says.
"There are a lot of things that are uncertain in the climate model, and probably the biggest uncertainty is really what the policy is going to be, how much CO2 is going to come into the atmosphere," he said.