Are climbing perch a major incursion threat for Australia?

June 2015

Imagine a fish that can live up to six days out of water, crawl across dry land, and choke any animal that tries to eat it. No need to imagine – such a fish is alive and well and threating to make its way to the Australian mainland.

Native to south-east Asia, climbing perch (Anabas testudineus) has spread through Indonesia and Papua New Guinea over the past 40 years. This aggressive fish is causing concern for Australia since it was washed into the waterways of two Queensland islands in the Torres Strait following heavy rainfall. They were discovered on the islands in 2006.

Despite being a freshwater species, the perch can also survive in brackish water. A labyrinthine chamber over its gills facilitates oxygen absorption, allowing the fish to remain on land for days at a time. Spiny, extendable gill covers are used to drag itself over dry land from waterbody to waterbody.

The gill covers have another function. According to scientist Dr Nathan Waltham from James Cook University, the climbing perch can flex their gill covers to catch in the throats of any animal trying to consume them. The perch can also inflate their body and block the airways of their predators.

Although it appears unlikely the perch could swim to mainland Australia, it is not unreasonable to assume the species may be inadvertently brought alive to Australia via fish catch or discarded bait in fishing vessels.

Dr Waltham said if climbing perch were not managed in the Torres Strait, the species could make its way to the northern Australia mainland.

Dr Michelle Christy, National Incursion Response Facilitator for Invasive Animals CRC, is concerned that for these reasons, the risk of the fish being brought to Australia and surviving are high. “Once they establish, eradication will be almost impossible”.