While attending the Annual Meeting of the American Fisheries Society in Kansas City in August, I visited the vendors, especially the electrofisher manufacturers. It is good to visit with those I know and to see new products. I don’t attend a lot of such meetings, but this was the first time for me to see a booth by ETS Electrofishing Systems LLC. Burke O’Neal of ETS Electrofishing retired and sold the company to his sons. Mark O’Neal now operates the company, which had a slight name change, and moved it to Madison Wisconsin. Burke and I never met, though we had corresponded by email and had talked on the phone over the years. We even collaborated on some testing of voltage gradient probes and of backpack electrofisher anodes. In August, it was my privilege to meet Mark.

ETS now manufacturers an 82 peak amp, high-conductivity version called the MBS-82. It is an upgrade from their former 72-amp high-conductivity version and also has a larger internal circuit breaker. The 82-amp version has been their standard high-conductivity model since August 2015. The new development is a high-voltage version for use in lower conductivity water. This new version, which was in beta format for the AFS meeting, has three voltage ranges – 1000, 600 and 300 volts – to cover a very wide range of water conductivity. The expected current outputs were reported as 30, 40 and 82 peak amps for the 1000, 600 and 300 volt ranges, respectively. While advertised performance is somewhat informative, I wanted to see actual performance data. So, I talked Mark into doing some extensive testing of his new unit over a wide range of resistance to simulate a wide range of water conductivity. This blog shows those results.

The unit was subjected to various electrical loads (resistances) until cutoff. The static electrical loads were supplied by combinations of oven heating elements in bench tests by ETS. For each resistance, the unit cutoff was recorded as a pulsator voltage or current limit or as a generator overload. Overload means the generator locked out from overloading or a breaker tripped. The generator was a Honda EU7000i used with an ETS Inverter Filter. This testing was done similarly to that conducted by Martinez and Kolz (2013), Performance of four boat electrofishers with measured electrode resistances for electrofishing boats and rafts, North American Journal of Fisheries Management 33:32-43. For that paper, they tested the Smith-Root VVP 15B and GPP 5.0, the ETS Electrofishing MBS 1D-72A and the Midwest Lake Electrofishing Systems Infinity pulsators using static loads produced by electrical baseboard heaters. Therefore, the results presented here should be comparable to the Martinez and Kolz study with one exception. The power versus resistance graphs produced by Martinez and Kolz relate to a special case where boats and rafts used spherical electrodes which were half-immersed. Thus, the total system resistances at 100 µS/cm, R100, for boats and rafts in their paper were 76 and 186 ohms, respectively. Those values are much higher than for a typical two-boom electrofishing boat in which the R100 may be about 35-40 ohms for a clean-hull boat with arrays of anode droppers. The higher resistance values used by Martinez and Kolz result in a shift on the X axis in their graphs versus the ones shown below in this blog.

New three voltage range ETS MBS-82 at Kansas City AFS meeting trade show. This unit has Bulgin connectors.

A closer view of the new ETS MBS-82 pulsator with the 1000, 600 and 300 volt ranges to cover a very wide range of water conductivity.

Peak power output versus resistance for the ETS MBS-82 boat electrofisher operated at 20% duty cycle. The white circles on the Boat Power graph represent the expected output, whereas the red circles are actual output data. From left to right, ascending diagonal lines are for the 1000, 600 and 300 volt ranges, whereas the descending diagonal lines are for the 30, 40 and 82 peak amp maximum current output expected for this unit and for the 1000, 600 and 300 volt ranges, respectively. The blue line is a power goal line expected for successful fishing with a given electrofishing boat at described in Miranda, L.E. 2009. Standardizing Electrofishing Power for Boat Electrofishing *in* S.A. Bonar, W.A. Hubert, and D.W. Willis (eds.), Standard Methods for Sampling North American Freshwater Fishes. American Fisheries Society, Bethesda, Maryland, USA. 335 p. This is for a standardized electrofishing boat described in Table A.1, p. 284 of Bonar et al. (2009). The Excel file used to produce this expected output is called Boat Power. The resistance at 100 µS/cm, R100, assumed for this graph is 35 ohms. Where the predictive white circles, or the actual performance data red circles, cross the blue line provides an estimate on the X-axis of the resistance operating range. The resultant conductivity range is calculated as the R100 x 100 then divided by the resistance value. In the Boat Power file is a conductivity calculator to make this an easy task. One can hover the cursor over one or more of the white circles to estimate the resistance at the crossing of the blue line then use the conductivity calculator to determine the associated water conductivity for that resistance. In this case, the expected conductivity range for this electrode resistance (R100 of 35 ohms) is about 20-1800 µS/cm. Any peak power above the blue threshold fishing line is excess to that needed for successful fishing.

Same as above except for a 25% duty cycle. Note that the resistance (and conductivity) range is identical to that for the 20% duty cycle graph above. The model (Boat Power Excel file) predicts that the maximum output of peak power is slightly less for the 1000 volt range when using a 25% versus a 20% duty cycle.

Same as above expect for a 40% duty cycle. A 40% duty cycle may be near the upper duty cycle limit for most fishing situations. A 40% duty cycle is thought to produce more taxis to the anode than a 20 or 25% duty cycle, so that may increase fish catch rates as fish are pulled from depth or from cover by the more attractive waveform. The idea of more fish attraction when using a higher duty cycle deserves more investigation. Note that the model predicts a reduced maximum output of peak power for all three voltage ranges – a flatter peak – and the actual test results confirm that. Also note that the predicted lower and upper resistance (and conductivity) ranges are the same as for the lower duty cycle pulses. The disadvantage of using a 40% duty cycle is the greater average power demand on the generator and pulsator.

Same as above except for 50% duty cycle. Only at this relatively high duty cycle is there an impact on the operational conductivity range, according to this model. Now the maximum output of peak power is estimated to be a little above 10,000 peak watts. Be aware that this graph is a log-log plot, so the actual predicted power may be more than it appears. The actual data suggest that the unit exceeded the model predictions in the range of about 3-12 ohms. The estimated lower conductivity (higher resistance) range remains at about 20 µS/cm. However, the estimated upper conductivity (lower resistance) dropped to about 1400 from about 1800 µS/cm when using 50% duty cycle setting. Again, an upper limit of duty cycle may be 40%; a higher duty cycle was used here to demonstrate its effect on predicted and actual power output.

As is clearly shown from these four graphs, the unit performs basically exactly as predicted by the Boat Power model. The correspondence is remarkable. Mark said that he checked some of these results with a second unit, and they both performed the same. Though it is easy to estimate the lower and upper conductivity points from investigation of where the white circles cross the blue line on the resistance axis, there is an even easier way of visualizing that range. There is a conductivity version of Boat Power shown in the graph below which makes the process of estimating the conductivity range even simpler.

This graph uses the same input data as for the 25% duty cycle graph above except this version of Boat Power has ambient water conductivity on the X axis to more easily display the expected conductivity range for this pulsator. Using an R100 value of 35 ohms, the lower conductivity expected operating range for the 1000, 600 and 300 volt ranges are 20, 40 and 115 µS/cm, respectively. The upper conductivity operating range for 300 volt range, i.e. for 82 peak amps, is 1800 µS/cm. This assumes fully successful fishing according to the blue line from Bonar et al. (2009). In other words, these conductivity values correspond to where the white circles cross the blue line. Changes could be made to the electrode configuration to alter this conductivity operating range, but these model input values appear to be a realistic basis for comparison. So the expected overall operating range for this unit is 20 to 1800 µS/cm, and that should cover almost all boat electrofishing situations in fresh water. Also shown on this graph are approximate voltage range shift points for use in waters of various water conductivity. Note that any values above the blue line are excess to the expected needs for satisfactory fishing. One merely needs to set the applied voltage so that power output is near the blue line.

The Boat Power file pretty accurately predicts actual boat electrofisher output over a wide range of resistance or conductivity. It also allows us to investigate alternative scenarios, to ask “What If?” questions. For instance, the graph above relates to electrode modification for use in higher conductivity water than the prior 1800 µS/cm estimate for fully successful fishing. The model output above is an estimate of peak power output if only one of the two anode arrays is used. That increases the R100 value from 35 to 58 ohms. Everything else is the same as for the graph immediately above. Note that the expected output values have been shifted to the right, to a higher conductivity. For the higher R100 value when only one anode boom is energized, the new expected conductivity range is 28-2300 µS/cm. Of course, the effective fishing zone may be smaller with only one anode array versus using both anode arrays, so there may be some trade-off in capture efficiency, but one could be expected to fish in higher conductivity water if using only one boom. Another approach to increase resistance so as to allow fishing in water conductivity higher than 1800 µS/cm is to employ both anode arrays but to pull some of the droppers from the water. That may affect the electrical field and the effective fishing zone relative to using a full complement of anode droppers. The scenario presented in the graph above is but one electrode modification; let me mention one other anode modification actually used in practice. First, I should mention that Mark conducted the same testing to the two-voltage range MBS-82 pulsator and found the same results as for the three-voltage range unit except that the former lacks the 1000 volt setting. Chas Patterson of the Oklahoma Department of Wildlife Conservation has used the two-voltage range MBS-82 in waters of about 2500 uS/cm by raising the anodes so that the droppers are barely immersed. That raises the overall resistance and counters the high conductivity water. That reduces the vertical extent of the field but allows successful fishing. Chas reports that his catch rates are similar to what they observed with a Smith-Root GPP 7.5.

The new, three-voltage range ETS MBS-82 model evidently performs as designed, and the Boat Power Excel file predicts and documents its performance quite well. Mark mentioned that the voltage range dial on the three-range pulsator will be High, Medium and Low because the actual output – nominally 1000, 600 and 300 volts – depends on generator type, load and settings. One last thing: Mark may call the three-voltage range pulsator the Trident.