The Risky Business of Electric Fishing

Electric fishing is a highly efficient method our Freshwater Ecologists use to survey streams and determine what fish species are in the water, but as you can tell by the name, it is a risky business. Imagine a high power voltage running through a stream, enough to electrocute you, and then someone tells you to get in. Yes, you are wearing protective gear, but one false move and you could do some serious damage, particularly if you haven’t had the necessary training to carry it out successfully. Which is why four members from the 4Sight Ecology team (Jade, Shannen, Ollie and Hannah) recently went on a NIWA run course to learn how to safely master the technique.

Taking place in Taupo, the course spanned two days and covered the theory and practical components of electric fishing, followed by an exam. So, with a lot of excitement and anticipation, the team packed up their protective rubber waders and headed down to Taupo to learn about the important health and safety risks associated with electric fishing, how best to mitigate these risks, and then adorned themselves in protective gear, strapped the machine onto their backs and got stuck into the fishing - under the expert guidance of their instructor Phil, of course.

Breaking it down, how it all works, is there needs to be a power source and a resistance connected by wire to start the process. In this case, an electric fishing machine (EFM) supplies the power source through a wand (anode) which is submerged under water in one section of the stream, and the water provides the resistance while the connected cables/earthing strap (cathode) help to conduct the electricity around the circuit. As a result, this conducts an electrical current through that specific reach of the stream and hence the need to be very careful not to touch the water and wear protective rubber gear when doing so!

This is where it gets technical, as the voltage the fish will receive is dependent on factors such as the fishes size, its distance from the EFM and its orientation to the electric field, so it requires some quick thinking from the Ecologists as to how to adjust the output settings of the EFM. The electrical current interferes with the fishes nervous system, causing their muscles to contract and ultimately swim towards the wand (anode) of the EFM. And as the Ecologists make their way down the stream, the ‘stunned’ fish are carefully collected in a net where they can then be measured and their species recorded before being released back into the water - once that reach of stream has been successfully fished.

Electric fishing makes for a very accurate, safe, and time effective way of surveying streams. The team were lucky enough to catch a couple of big fish on the day and found the course to be incredibly useful. So all in all, it was a very successful couple of days for the team and 4Sight now has a total of 6 qualified electric fishers - well done everyone!

If you’re interested in finding out more about our expertise and other methods of conducting ecological surveys, check out our Ecology team’s profiles here and in the meantime check out some pictures from the day below: