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Boat Fleet Fishing Thresholds

Jim Reynolds and I just taught a boat electrofishing course in Redding, California at Whiskeytown Lake. That provided some threshold fishing data for voltage, current and power for each of four electrofishing boats. One can standardize by power using any of the three parameters. Which parameter is less variable among a fleet of boats?

Three of the four boats were similar in size (18 feet long by 6 or 7 feet wide) with unpainted hulls, and one was smaller (14 feet long by 4.5 feet wide) and had a painted hull. All boats had spider anode arrays and the boat hulls were the cathodes. However, the boats generally had auxiliary cathode skirts.

Redding larger

This is one of the three larger boats. Notice the cathode skirt.

Redding small

This is the one small boat with a painted hull.

Small w skirt

The small boat with a painted hull would have had a high resistance except for the auxiliary cathode skirt with reduces the overall resistance (especially for the cathode), concentrates the electrical field near the bow, and results in a higher proportion of the power to the anode.

Boat size Rs

This table provides the size of each boat and the overall system resistance (Rs) at the ambient water conductivity of 68 uS/cm. Electrofishing pulsators were SRI GPP 5.0 units for all of the boats except Big Stunna which had an SRI GPP 7.5.

V calibration

We used an independent meter (oscilloscope) as a voltage calibration based on the selected voltage range and for Percent of Range settings of 10, 20, 40, 60, 80 and 100. Above are the outputs for two of the boats, each with a GPP 5.0. The differences in actual output peak voltages for the same voltage ranges and POR settings were interesting. That underscores the need for accurate peak metering or at least the need to calibrate pulsator output.


Here are the threshold fishing results for each boat. Threshold peak voltages were calculated from the pulsator settings and the voltage calibrations using the scopemeter. Thresholds for peak current and peak power were calculated from the peak voltage values and the system resistance data. Results in the table for average and standard deviation are shown rounded in the table but the actual values were used in the calculation of the coefficients of variation.

Coefficients of variation, as shown in the last row above, are the fairest way of comparing relative variation of voltage, current or power among the fleet of four boats. By far, the lowest coefficient of variation among the four boats was for peak current. For a given boat, one can standardize by power using voltage, current or power — as long as the electrode configuration remains unchanged. However, for a fleet of boats, the clear indication from these results is that one should standardize by power using peak current.

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© 2015 Thread One Page. Imagery: Tom Rayner, Alan temple, Richard Pearson, Paul Godfrey, Roger Scott, John Rayner.