Tropical fish predicted to move to Far South Coast as waters warm

Tropical fish species have been gradually increasing in numbers on the Far South Coast, and research has indicated over the next few decades water temperatures will be warm enough for them to live there permanently. 

This is the subject Kai Paijmans, who was raised in Tathra and attended school in Bega, is looking into as part of his PhD at the University of Wollongong.  

Between February to May this year, he conducted scuba diving surveys once a month at several locations on the Far South Coast, finding 15-20 tropical fish at the sites each time. These sites included Narooma Breakwall, Kianinny Bay in Tathra, Bar Beach in Merimbula and Shelly’s Beach in Eden. 

“It is a very healthy area, compared to areas closer to Wollongong and Sydney; there’s definitely more fish down south,” he said.

The most common tropical fish he found was the Indo-Pacific sergeant, a fish that grows to about 20cm and has a white body with five black bars, which formed the focus of his investigation. 

While its native region is north of Coffs Harbour, when it is in its larval stage it can get transported down the East Coast. 

Mr Paijmans found when it becomes displaced from its native region the sergeant prefers to be with other species rather than its own, which he said was most likely due to it receiving protection from predators and accessing food. 

“As climate change drives increasing sea surface temperatures, tropical fish moving south of their range will permanently move,” he said. 

“By understanding which species will adapt, we will be able to predict what the fish community looks like in the future.”

An Indo-Pacific sergeant. Photo: Alex Pike

An Indo-Pacific sergeant. Photo: Alex Pike

He said it was difficult to say what impact rising temperatures would have on sea life along the East Coast. On one hand, as it becomes too hot for tropical fish up north they may move south, which would allow them to survive. Although they may also compete with native species and push them out.

Mr Paijmans said while numbers of tropical fish species are increasing on the Far South Coast every year, it is not a quick process. 

“The research suggests sea surface temperatures in South East Australia will go up by approximately 1.5 degrees Celsius in the next 15-30 years,” he said. 

“That much of an increase would allow the tropical fish to survive.” 

Mr Paijmans has created a short video on his research as part of his PhD, which has been entered into a competition which if won will allow him to attend a national fish conference and share his findings with more researchers. 

To view and vote for the video, visit www.thinkable.org/submission_entries/YqDomj91

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