Sarah Farnsworth reported this story on Tuesday, June 2, 2015 18:40:00

MARK COLVIN: Australian ecologists at James Cook University say an aggressive and hardy fish from Papua New Guinea could pose a threat in Australia.



Discovered in 2005, the Climbing Perch, can live out of water for up to six days.



Now there are fears its making its way to Australia and leaving a trail of destruction behind it.



Sarah Farnsworth reports.



SARAH FARNSWORTH: It's a fish, so it doesn't have legs. But that isn't stopping the Climbing Perch from getting around.



NATHAN WALTHAM: It's hard gill plates can actually bend them forward, and with some sharp spines, if you can imagine, it will actually drag itself along the ground. So slowly walking from one waterhole across land, and eventually finding another waterhole.



SARAH FARNSWORTH: It can also hold its breath as it drags itself across land.



Dr Nathan Waltham is part of the TropWater team from James Cook University that's been monitoring the travel plans of the Climbing Perch, which has spread though Indonesia, Java and Papua New Guinea.



The species has now made its way to two of Australia's most northerly outposts - the Torres Strait Boigu, and Saibi Islands, and it's killing barramundi and catfish.



NATHAN WALTHAM: For a larger animal - a fish or a bird - consumes the Climbing Perch with these strong gill plates that can be flared out. The fish becomes lodged inside the throat of the other animal - be it a fish or a bird - and it can cause it to starve.



SARAH FARNSWORTH: Yet it's what Dr Waltham's team discovered on the islands last December that has them worried.



NATHAN WALTHAM: The water we were testing there was very, very salty. It was higher than what you'd find in the ocean, so it was hypersaline. And we also caught Climbing Perch during that survey.



So this to us sort of suggests possibly that being a freshwater fish, they have this ability to withstand saltwater conditions.



SARAH FARNSWORTH: Damien Burrows is also from Tropwater, and says there are concerns the aggressive and extremely hardy fish - which can hibernate in the mud of a dried waterhole for up to six months - could get to Australia.



But by hitching a ride rather than under its own steam.



DAMIEN BURROWS: They're freshwater fish, but they do can tolerate seawater. But nonetheless, they're going to swim I don't believe across the Torres Strait to Australia.



They would only come to Australia if people either carried them either in their boats or in their buckets, or some other mechanism. So people have to bring them here.



SARAH FARNSWORTH: If it does get here, what's the risk it poses to species in Australia?



DAMIEN BURROWS: Well I think the main risk is to some of our iconic fishery species like Barramundi and large catfish, and also various water birds.



We're particularly worried about the fish getting trapped in the throats of Barramundi and catfish, and a bird that would try and eat this Climbing Perch.



SARAH FARNSWORTH: So they could become a toxic, deadly snack for turtles and birds over here.



DAMIEN BURROWS: Sure, yep. And aquatic snakes as well have been recorded with Climbing Perch in them.



SARAH FARNSWORTH: The TropWater team is now trying to work out the maximum salt, temperature and oxygen levels the fish need to survive so they can try and stop its travels south.



MARK COLVIN: Sarah Farnsworth.