Seafood News - Industry Events - Seafood Market

ABC OnlineAustralian News    27/11/2004 08:57:46

Ian Townsend

PETER CAVE: Fishermen in Queensland fear a human hand is helping a verminous fish to overrun the state's rivers and dams. New surveys are finding the exotic fish tilapia has spread further than biologists thought. The fish has been likened to the canetoad in its effect on native species.

Fishery authorities are now worried that the approaching wet season could end efforts to control the tilapia invasion in some of Queensland's biggest river systems.

Ian Townsend reports.

IAN TOWNSEND: The Tilapia fish originally comes from Africa and has been a favourite in the aquarium trade for many years. It's also good to eat, it's on menus around the world, and it's a prized farm fish in many countries.

But in Australia, it's gone from a nuisance to a dire threat to native fish, especially in tropical Queensland, where it seems, now, to have infected many of the wild rivers.

PETER JACKSON: In the last few years they seem… indications are that they're spreading at a more rapid rate than they were before. It seems to be that the tilapia populations we're finding are at the top of river systems, suggesting that someone is going around and putting them in there deliberately.

And it's the worst thing that you can do, because once they get into a river system it's almost impossible for us to get them out.

IAN TOWNSEND: Peter Jackson is a freshwater fisheries scientist with the Queensland Government, who's found the fish now in one of Queensland's biggest river systems, the Burdekin.

PETER JACKSON: The fact that they breed rapidly, they breed a couple of times a year, they're mouth breeders so they have good survival, you get large numbers of them. They're going to interact with native species in terms of competing for resources.

Research needs to be done to really determine exactly what their impact is, but we're taking the precautionary approach and saying well, let's not find out, let's keep them out of as many river systems as we can – because once they do get into a river system, unless we find out really quickly, and they're in an isolated area, our chances of getting them out are almost zero.

IAN TOWNSEND: We're coming up to the wet season at the moment. What's the concern there with the fish that are being found at the head of the Burdekin, for instance?

PETER JACKSON: Well, we think that probably in the Burdekin, it's too late.

IAN TOWNSEND: The plan now is to try and protect the remaining river systems in Queensland?

PETER JACKSON: That's right, that's right, to stop people from putting them in there. Our pest fish strategy has always been one of trying to contain fish to where they are and not let them spread. Unfortunately recently it's obvious that someone's been spreading them around.

IAN TOWNSEND: That's a shame because Queensland has some unique native freshwater sporting fish – the sooty grunter, and the jungle perch, not to mention barramundi. The thought of losing many of these fish to tilapia is horrifying anglers.

David Bateman is the Executive Officer of the amateur fishing lobby group, Sunfish.

DAVID BATEMAN: They actually exist in a lot of areas with only six inches or ten centimeters of water.

IAN TOWNSEND: Where have you seen them?

DAVID BATEMAN: I've seen them in the drains of Townsville, I've seen them at North Pine dam.

IAN TOWNSEND: When you say the drains in Townsville, what do you mean?

DAVID BATEMAN: I've seen them almost in the centre of town in some of the drains there, fish of around 10-15 centimetres in length, with nesting holes in the floor of the actual gravel-type drains. They're quite visible. You just walk along the side of the drains on the concrete path and you look over the side and there they are.

IAN TOWNSEND: How do they actually compete with other fish? Do they actually eat them?

DAVID BATEMAN: No, as far as I know, they're a weed eater, but what they do is disturb the floor of whatever stream they're in by building… they build a circular nest, an erosion type thing, but they also compete for food with any of the other weed eater type natural fish in the areas.

IAN TOWNSEND: This is quite a disaster isn't it?

DAVID BATEMAN: Well, it will be of they take over the creeks and streams and rivers.