A fish that can move across dry land is threatening to make its way to Australia from Papua New Guinea and could pose a threat to local birds and marine life, scientists have warned. The climbing perch, an invasive and exceedingly aggressive freshwater species that "walks" between waterholes, can survive for up to six days without water and has already made its way to islands off Australia.Scientists monitoring the fish's progress now believe it can survive in salt water and is set to head for the Australian mainland, possibly by catching a ride in a fishing boat.The fish was discovered on two small islands close to Papua New Guinea in late 2005."I still think the chances of it getting to Australia by swimming are low," said Dr Nathan Waltham from James Cook University."There is more chance it will arrive in the bottom of a fishing boat or as discarded live-bait fish."The climbing perch, or Anabas testudineus, has tended to overpower native species and can hibernate in the mud of dry creek beds for up to six months.It is able to destroy larger creatures by swelling up after being swallowed to block the predator's throat, thereby choking adversaries or forcing them to starve."It does seem to be able to handle a little bit of salt," Waltham said.Herbert Warusam, a ranger on Saibai Island, a Torres Strait island north of Queensland, said: "We are monitoring climbing perch in our wetlands. It is important we don't let them travel beyond our island." ..