Tropical fish are invading some Australian waters thanks to climate change, a new study released on Tuesday has found.
The fish are travelling the Australian ecosystems as larvae caught in the Eastern Australian Current, a University of Adelaide study of shallow-water fish communities on rocky reefs in south-eastern Australia found.
"These larvae would not normally survive in the cooler Australian ocean water, but the warming Eastern Australian Current keeps the baby fish warm and increases their likelihood of survival," chief investigator of the study Ivan Nagelkerken said.
The tropical fish were not impacting the ecosystem at present as they did not grow to their maximum size, but could in the future, the researchers warned.
"However, under increasing future ocean warming these tropical fish will eventually grow to their full size, and their diets will start to overlap more and more with those of temperate fish," co-investigator David Booth of the University of Technology Sydney said.
"It is the expectation that these tropical fish will be permanently established in temperate Australia, where they will become serious competitors with the native temperate fish that have historically lived there."
Nagelkerken says similar changes in water temperature were also being seen in south-western Australia and overseas.
The fish migration observed in the study was "an ongoing process that has strengthened in the last few decades due to ocean warming," he said.
The broader impacts on the ecosystems the fish invade were not yet clear.
"Tropical herbivores overgraze temperate kelp, but for the tropical invertebrate eaters, we are not sure yet what it means for the ecosystem itself," Nagelkerken said.