Fisherman’s Friend

There’s a fish species invading the inland waters of Australia like a plague. Tilapia, an African freshwater fish, is moving in and the sensitive native fish are quickly being out competed. Tilapia is a controversial little fish, since it is an excellent fish for eating: protein-rich, a rapid breeder and apparently quite tasty. It has been introduced to Australia for this very reason. The drawback however is that it overtakes most native species, often wiping them out completely. These traits have earned it the dubious title of the ‘rabbit of the river’.

Here in far north Queensland Tilapia has just started to move in and since it has the media's attention (the bad news always sells better than the good) there is a flurry of government driven activity to try and do something about it. Since the Wetlands is part of the headwaters of the Mitchell River, the largest river in Queensland (when it flows anyway), it is only a matter time before the Fisheries Department turns up on our doorstep.

They’re here to survey our lagoons for Tilapia and being the curious person that I am I offer to tag along and give them a hand. On the drive out to the lagoons I wonder how they intend to ‘survey’ the fish. A short questionnaire perhaps, which each fish has to fill out and return? Or maybe a one-on-one interview, anonymous of course, where native fish can dob in Tilapia living incognito in their communities?

I soon discover that their preferred technique is nothing so subtle. We’re using “electro-fishing”. The two guys from Fisheries have a custom built boat, rigged up with a high-voltage generator. Two long poles reach forward off the front of the boat and from these several wires dangle into the water. As we move around each lagoon, the captain fires up the generator, pumping a 1000 volt charge into the water. This forms a kind of electric net several meters in front of the boat and fish caught in this are stunned for a few seconds and can then be scooped onto the boat via a net. This is my kind of fishing!

I’m handed a pair of gumboots, thick rubber gloves and a pole-net and then I’m sent to the front of the boat for “catch duty”. The boat’s rigged for safety, with rubber coated railings and carpeted floors. We also have foot pedals that we have to keep pressure on for the electricity to flow. Should one of us fall in, the pedal would then be released, and the voltage would (hopefully) stop. It’s a cool little toy.

It’s an odd spectacle: fish get caught in the electric field then dart briefly around in a circle, like a dog chasing its tail, before drifting up to the surface, comatose where we reach down with our nets and quickly scoop them into a waiting bucket of water. We pull out fish of all shapes and sizes, from tiny native catfish to sooty grunters and, the catch of the day, one well-sized northern Saratoga. In the shallows, crayfish dart away in a panic but none are stunned.

The end result is a bucket full of mismatched fish and we go through each, taking measurements. We find no Tilapia and in fact, we find no pest species what-so-ever. The Wetlands is given an excellent bill of health as far as the fish and water quality is concerned. Heartened by this news I ask the Fisheries guys what measures we should take to keep Tilapia out. Perhaps some nets across the channels or traps that are regularly checked, providing us with early warning and allowing us to shut the channels and prevent further spread while we clean up?

I’m told there’s nothing that can be done to stop the spread. Add to this that there’s nothing that can be done to remove the fish once they’re in and it doesn’t look like there’s many options available to us. Perhaps I'm getting cynical but I do wonder whether it's worth spending wads of cash zapping hapless fish when there’s nothing that can actually be done with the resulting knowledge. I reckon I could think of a few more worthy causes to put that cash towards. Still we all had a good day out fishing and that’s the important thing.