Field Notes
U.S. Fish & Wildlife Service
Field Notes Entry   
Electrofishing settings research for Asian carp
Midwest Region, September 21, 2011
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MLES Electrofishing System is Used to Research Carp Taxis
MLES Electrofishing System is Used to Research Carp Taxis - Photo Credit: Dr. Jan Dean

Coming from the Missouri River, it is common to see jumping silver carp in the backwater areas and tributaries. For the most part, however, you can steer clear of them or at least predict where not to go.  I had my first experience on the Illinois River and now I understand. Put simply, the novelty of jumping carp wears off quickly in the Illinois River! If one wonders why no one is using the Illinois, its because the carp are unavoidable, they aren’t just in the tributaries or backwaters, they are everywhere! We had to set goby traps up and down the river, and every stop one would have to dodge fish bullets, or continually evacuate the bleeding, flopping, sliming bain of our rivers.

We have been challenged in our part of the river to determine how to monitor, catch, kill or remove these fish and we are constantly working on improving and expanding our techniques. Our best monitoring tool is electrofishing, but up to this point, carp have been more likely to evade our electrofishing boats at long distance or stay just outside the reach of our dip nets. Some species of fish react  differently to electricity than closely-related species (i.e. channel catfish vs. flathead catfish, and, common carp vs. silver carp). One can use many methods to transmit the electricity (old crank telephones or highly specialized units with generators) and depending on the fish, one delivery system will work where one will not. With the help of Dr. Jan Dean from Nacotish National Fish Hatchery and contracted physicist, we feel that we have an electrical field that will allow us to target carp.

Using laboratory techniques to whittle down thresholds for taxis (muscle control) and immobilization, we came up with some values that can target carp in the field. These values were tested in the field successfully, and, for the first time, we can apply taxis and actually dip fish rather than deter fish around the boat. Dr. Dean points out after three days working with our office that there is a small threshold between immobilization, taxis and fright, and tipping one way or the other can impact whether or not we see fish. We were able to micro-tune our settings using new technology- the MLES infinity electrofishing box developed by Midwest Lake Management. The box technology is unique because it gives the user total control and allows you to choose digitally your waveform by way of infinite frequency, duty-cycle settings, and unit voltage settings. Targeting a range of 80 to 40 pps with half the duty cycle of the frequency will give the operator the desired waveform. Couple these settings with voltage in the range of 120-240 for a power around 3000-7000 Watts and you’ll see the carp rolling. We are still experimenting with effects on large versus small carp as it seems that the power of the larger carp can propel them (even under taxis) out of the immobilization field. We are hopeful, that now with these lab and field tested settings we can begin a more effective monitoring program that will allow us to assess areas where carp are even less abundant.

Contact Info: Wyatt Doyle, (573)876-1911 ex 111, wyatt_doyle@fws.gov
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