Meet the walking fish making its way to Australia
Able to survive out of water for up to six days, scientists fear the aggressive climbing perch may reach mainland Australia from Papua New Guinea, potentially harming native species.
A freshwater fish capable of surviving out of water for up to six days may also be able to survive in salty water, prompting scientists to warn that the aggressive climbing perch could make its way to mainland Australia from Papua New Guinea.
The fish, which can crawl across dry land and hibernate in dry creek beds for up to six months, has already made it to two small Torres Strait islands in Australian territory.
However ecologists hold serious concerns for the fate of native species if the climbing perch makes it to mainland Australia.
“They can breathe on land, they can walk across land with their gills and they can handle salt,” said James Cook University aquatic ecologist Nathan Waltham.
The climbing perch was discovered in late 2005 on Boigu and Saibai Islands, two of Australia’s most northerly outposts just four and six kilometres respectively from the Papua New Guinea mainland.
On a fieldtrip to the islands in December, James Cook University scientists, including Dr Waltham, observed the fish in salty water holes which raised the alarm.
“That trip was at the end of the dry season so the water that remained in the wetlands was very salty,” Dr Waltham said. “In fact it was twice the level of salt we have in the ocean and climbing perch was still there.”
He said the invasive species, native to southeast Asia, was highly mobile, able to drag itself between waterholes where it quickly became established and a threat to other native fish.
Deceased barramundi and catfish have been found on Boigu and Saibai Islands with climbing perch in their digestive systems. The climbing perch’s strong gill cover killed the predatory fish because it lodged in their throat.
Native to southeast Asia, over the last 30 to 40 years the fish has spread through Indonesia, Java and Papua New Guinea.
However the climbing perch is not just a threat to aquatic species. The noxious fish is also problematic for birds which similarly have trouble with the fish’s gill covers which lodge in the throats of birds trying to eat them. This causes fatal injuries.
Despite new evidence that the climbing perch can survive in salty waters, Dr Waltham said the most likely way the fish would reach the mainland was by being pulled aboard a fishing boat or being discarded as live-bait fish.
“I still think the chances of it getting to Australia by swimming are quite low,” he said.
James Cook University researchers have just begun testing to establish what the salt and oxygen tolerance levels are for the climbing perch. They are also testing water temperature tolerance levels for the species.
If ecologists can establish the maximum salt, temperature or oxygen levels for the fish then scientists have a target to hopefully control the climbing perch’s wild population and its march south.
Anabantidae – Integrated Taxonomic Information System.
Climbing gourami commonly called the climbing gouramies or climbing perches
Anabas testudineus or ‘Koi in bengali’ fish in the Assamese language