My family's contribution to last year's Lake Burley Griffin Carpathon was purely monetary. My sons and I got in reasonably early but still had to sort of squeeze our way into a bit of shore space on Canberra's main lake. We decided it would be good to be near the action so stayed near the weigh station where literally tonnes of fish came in: none of it from us.
I'm convinced I produce a fish alarm pheromone that is transmitted from my fingers to either bait or lure. My sons lack of fishing success indicates that this is a genetic trait. It works on all species of fish, freshwater and saltwater. Given the amount of fishing gear we've bought, we reckon fish cost our family an average $850 per kilo.
So from experience, I knew that I wouldn't personally make a significant contribution to ridding Lake Burley Griffin of carp. New research from Queensland DPI&F indicates that fishing competitions in general don't make a dent on the population. Researchers Andrew Norris and Michael Hutchinson tagged fish in areas where a number of carp fishing contests were held. They then measured how many of the tagged fish were caught by competitors and how many they could retrieve with a one-day electrofishing effort. Intense fishing pressure like a competition removed 0.5% to 1.8% of the carp in an area. Electofishing took up to about 15% of the population.
We know a lot more about carp removal than we did only a few years ago. Sex and food are looking to be be a big part of things (surprise, surprise!). Queensland and Tasmanian researchers have had great success with "hotting up" female carp with hormones. University of Minnesota researchers have shown that carp can be very quickly trained to corn feeding at regular intervals, enabling them to take out large numbers. New South Wales researchers have identified that carp breed in quite limited places that can be identified and targeted. The flow of water can influence behaviour of carp in the opposite way to Australian native fish and South Australian researchers have used this differentiation to effectively leave carp high and dry in drained wetlands. Tipping the balance to predators may also be important in order to keep carp down.
It won't be long before we can target and remove high percentages of carp in a system and probably prevent some replacement through breeding disruption. Lake Torrens in Adelaide is under research in this way.
Even with the knowledge that fishing doesn't make a big dent, it is still fun (even for those of us that don't catch anything). So if you are near Canberra, enter the Canberra Monster Carpathon this Sunday and enjoy. Entry details here.