AS IF cane toads aren’t enough, an aggressive, fast-breeding invasive fish species is muscling its way into the waterways of northern Australia.

The Mozambique tilapia (Oreochromis mossambicus), introduced into Australia as an aquarium fish, has spent the past 30 years entrenching itself in waterways throughout Queensland and Western Australia, researchers say.

While they may look beautiful in a tank, in the wild tilapia compete with native fish, out-breeding and out-eating them.

“In one case, nine tilapia went into a pond system,” says Invasive Animals Co-operative Research Centre chief operating officer Andreas Glanznig.

“When they poisoned it several years later, the only thing living in there were tilapia - and they dragged out 13 tonnes.”

From cane toads and rabbits to foxes, cats and buffalo, many introduced species have made Australia home, kicking out locals in the process.

“The number of exotic fish that have invaded Australian waters has jumped from 22 in 1990 to at least 34 today,” Mr Glanznig says.

“All but one of these newcomers originated from the aquarium trade. (People) should not dump unwanted invasive aquarium fish that can have a huge impact on aquatic ecosystems and wildlife.”

Australia’s experience with carp has already demonstrated just how devastating a problem introduced fish can become.

While not an aquarium species, the common carp (Cyprinus carpio) is one Australia’s most infamous freshwater fish invaders.

Introduced into Australia in the early 1900s for food and recreational fishing, extensive flooding has seen carp escape from farm dams and move into the waterways, including the extensive Murray-Darling river system.

“Carp create conditions that aren’t as conducive to native fish and therefore numbers (of native fish) fall,” Mr Glanznig says.

He believes this demonstrates the need to control the tilapia before they become the “carp of the north”.

Efforts to eradicate tilapia are being made more difficult by the actions of unthinking locals.

Last month, officers from the Queensland Department of Primary Industries and Fisheries found tilapia they believe had been illegally released in the

Gulf region.

“Most tilapia infestations are caused by people moving fish between waterways,” Queensland Department of Primary Industries and Fisheries biologist Malcolm Pearce says.

“Once established in a waterway, they are almost impossible to eradicate,” he said.

“If the spread of the fish isn’t controlled, tilapia could significantly affect our commercial and recreational fisheries.”

Source: Adelaide Now