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Performance of Four Boat Electrofishers with MeasuredElectrode Resistances for Electrofishing Boats and RaftsPatrick J. Martinez a & A. Lawrence Kolz b ca U.S. Fish and Wildlife Service , 764 Horizon Drive, Grand Junction , Colorado , 81506 , USAb 447 Whitetail Lane , Grand Junction , Colorado , 81507 , USAc Retired1Published online: 09 Jan 2013.

To cite this article: Patrick J. Martinez & A. Lawrence Kolz (2013) Performance of Four Boat Electrofishers with MeasuredElectrode Resistances for Electrofishing Boats and Rafts, North American Journal of Fisheries Management, 33:1, 32-43, DOI:10.1080/02755947.2012.739985

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North American Journal of Fisheries Management 33:32–43, 2013C© American Fisheries Society 2013ISSN: 0275-5947 print / 1548-8675 onlineDOI: 10.1080/02755947.2012.739985

ARTICLE

Performance of Four Boat Electrofishers with MeasuredElectrode Resistances for Electrofishing Boats and Rafts

Patrick J. Martinez*U.S. Fish and Wildlife Service, 764 Horizon Drive, Grand Junction, Colorado 81506, USA

A. Lawrence Kolz1

447 Whitetail Lane, Grand Junction, Colorado 81507, USA

AbstractA misconception in the description of boat electrofishers has resulted from specifying their operational capabilities

over ranges of water conductivity without any reference to the electrode configuration with which they will be used.Water conductivity alone is not the valid or most informative electrical variable for defining the operational charac-teristics of a boat electrofisher and its power supply, but its persistent usage has displaced the correct terminology:electrode resistance measured in ohms. Consequently, inherent design limitations and actual operating characteristicsfor specific boat electrofishers and their power sources as dictated by electrode resistance have remained undefined.Recognizing this dilemma, total electrode resistance (anodes plus cathodes) was measured for two electrode configura-tions, metal-hulled boats and inflatable whitewater rafts. Knowing the electrode resistances for these two electrofishingcrafts (conductive versus nonconductive hulls) facilitated complete systems’ analyses, provided an analytical under-standing of equipment settings, and identified the power capabilities for four boat electrofishers manufactured in theUSA. In accordance with the equivalent electrode resistances of these two craft types, electrical load measurementswere performed for four boat electrofishers (Smith-Root VVP 15B and GPP 5.0, the ETS Electrofishing MBS 1D-72A,and the Midwest Lake Electrofishing Systems MLES Infinity) to examine their pulsed-DC operational capacities overa range of simulated water conductivities. Graphical plots for each craft type provide an approximation of the rangeof water conductivity over which each boat electrofisher would be expected to sustain a power level that meets orexceeds power goals for successful electrofishing. This information should improve the understanding of the role ofelectrode resistance in dictating power demand from boat electrofishers. It should also aid in the selection of a boatelectrofisher based on its capacity to sustain standardized power levels in the electrofishing craft in which they willbe used and over the range of water conductivities encountered.

Boat electrofishers are special purpose, high-voltage powersupplies manufactured for the singular purpose of facilitating thecapture of fish. Electrical specifications for boat electrofishersmarketed in the USA are generally insufficient for adequatelyjudging the actual operational or performance characteristics ofvarious models (Kolz 2008). Perhaps this explains why elec-trofishing personnel often purchase equipment based upon theadvice, experience, success, or frustrations of colleagues ratherthan the advertised specifications available from manufacturers.Without technical support to verify boat electrofisher outputs,

*Corresponding author: patrick martinez@fws.gov1Retired.Received June 14, 2012; accepted October 3, 2012Published online January 9, 2013

operators must assume the responsibility for understanding theelectrical features of inadequately specified boat electrofishers(Kolz 2008).

Lacking specific criteria regarding what information is war-ranted in the marketing of boat electrofishers, the degree of riskand user satisfaction is obviously at the purchaser’s discretion.Further complicating the decision about which boat electrofisherto purchase is the misconception specifying that boat electrofish-ers operate over ranges of water conductivity that lack any ref-erence to the electrode configuration with which they will be

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EVALUATION OF FOUR BOAT ELECTROFISHERS 33

used. Unfortunately, water conductivity alone is not the valid ormost informative electrical variable for defining the operationalcharacteristics of a boat electrofisher and its power supply, but itspersistent usage has displaced the correct terminology: electroderesistance measured in ohms. Electrofishers are not designed todissipate power in water conductivity; rather they must supplypower in accordance with the electrical resistance created bythe immersed electrodes (Beaumont et al. 2005). Novotny andPriegel (1974) presented graphical methods for determining theresistance of several electrode configurations, and Kolz (1993)described measurement techniques for electrode arrays of anysize and shape. Unfortunately, the significance of these funda-mental concepts is often underestimated (Reynolds and Kolz2013), and resistance measurements have often been ignored,seldom applied, or assumed to be irrelevant.

Electrode resistance is perhaps the most misunderstood andignored variable in the electrofishing literature. As a conse-quence, the operating limits for boat electrofishers and theirpower source, as dictated by electrode resistance, have remainedundefined and have probably contributed to a “black box” (i.e.,turn the knobs and see what happens) approach in selecting andsetting the adjustments. The reality is that few electrode configu-rations (spheres and cylinders) can be solved with exact theoreti-cal equations to determine their resistance (Novotny and Priegel1974; Beaumont et al. 2005). However, the empirical alternativeis to measure the applied peak voltage and peak current (amps)for any submerged electrode configuration and thereby calculateits in-water resistance (ohms) with Ohm’s Law (total electricalresistance = peak voltage divided by peak current; Kolz 1993,2008; Beaumont et al. 2005). Examples of electrofishing sys-tems that may differ in terms of their electrical resistance includebank electrofishers or barge set-ups having single or multiplehand-held anodes, aluminum-hulled boats with multiple boom-mounted anodes, or inflatable rafts with anodes of varying sizeand configuration (e.g., droppers, rings, or spheres).

The research performed for this study was based on two elec-trode configurations, one for aluminum-hulled boats and one forinflatable whitewater rafts. This is not to imply that boats andrafts using identical electrofishers are or can be designed to havethe same catchability (conductive versus nonconductive hulls),as that is not possible (Miranda 2005). But, selecting a boat elec-trofisher brand and model that could be used interchangeablybetween these two styles of electrofishing craft in a multistateor multiagency electrofishing fleet would be operationally andfiscally desirable. Assembling an electrofishing system in a boator raft can be expensive, the boat electrofisher and its genera-tor potentially accounting for much of this cost. The ability fora boat electrofisher to be switched between crafts would alsofacilitate troubleshooting and the training of personnel in theselection of proper control settings for safely and effectivelycapturing fish.

For a boat electrofisher to be fully interchangeable betweentwo different crafts having different electrode configurationsof differing system resistance, it must be able to sustain stan-

dardized power output in accordance with the Power TransferTheorem (Kolz 1989) across the range of water conductivi-ties in which the fleet operates. Further, the output of a boatelectrofisher must exhibit an acceptable and stable waveform(i.e., pulse shape, duty, and frequency) that promotes effec-tive fish capture and does not contribute to fish injury, even atthe extremes of water conductivity encountered. By measur-ing electrode resistance it becomes feasible to perform circuitanalyses, test electrofisher settings, and identify electrofishingsystem power limitations for standardizing the in-water poweroutput for each of these two craft types. We tested four boatelectrofishers manufactured in the USA to determine their op-erational capacities via static electrical loads simulating the op-eration of electrofishing boats and rafts over a range of waterconductivities.

METHODSElectrofishing system resistance.—The electrofishing john

boat used in this study (about 5.3 m long, flat bottom, aluminumhull) served as the cathode and had two booms, each supportinga 23-cm-diameter anodic spheres. The booms extended 2.3 mfrom the bow and positioned the two anodes 2 m apart. Thewhitewater rafts (4.3–4.9 m in length) operated with a single,23-cm diameter sphere that extended 1.4 m beyond the handrail.The two cathodes (each composed of three, 0.6-cm diameterstainless steel cables, 1.2 m long), one dropped along each sideof the raft, were about 2 m apart and positioned 5 m aft of theanodic sphere.

The measurement of electrode resistance was performed withthe spherical anodes half-submerged about 12 cm below thesurface of the water. Weather and water conditions for thesemeasurements were ideal, the lake being closed to boating andlittle if any wind and wave action. The initial electrode resistancemeasurements for the boat and raft (R1) were taken at 745 µS/cm(δ1) ambient water conductivity. To facilitate comparison withother electrode designs (R2; in Kolz 1993), measured resistances(Ω) of the boat and raft were normalized to a water conductivityof 100 µS/cm (δ2; Dean and Temple 2011):

R2 = (R1 × δ1)/δ2. (1)

The power source for measuring the equivalent electrode resis-tances of the rafts and boats was a Smith Root (S-R) GPP 5.0,powered by its proprietary generator, operating in the pulsed-DC (PDC) mode. Peak volts and peak amps were measuredwith a Fluke Model 99B digital oscilloscope equipped with amodel 80i (1,000s) current clamp. The total electrode resistance(anodes plus cathodes, collectively) was calculated by the ratioof peak voltage to peak amps. These tests required wiring theelectrofisher’s output directly to the input of the oscilloscope viainsulated, high-voltage test leads (caution: do not try this with-out technical assistance). A current clamp provides a convenientmethod to monitor the current amplitude in a circuit without

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exposing and splicing into the system’s wiring. However,current clamps can distort the PDC waveform and may produceerroneous readings if the instructions provided in the operatingmanual are ignored and the transformer windings in the clampare allowed to saturate.

Boat electrofisher measurements.—We measured, via theFluke 99B, peak output voltage, current, and power for fourelectrofishers designed for use in boats: (1) the VVP 15B and(2) the GPP 5.0, both made by Smith-Root, Inc.,Vancouver,Washington, (3) the MBS 1D equipped with a 72-A high-outputcurrent option (ETS Electrofishing, LLC, Verona, Wisconsin),and (4) the MLES Infinity (Midwest Lake Electrofishing Sys-tems, Inc., Polo, Missouri). With the exception of the MBS 1D(which was new), the boat electrofishers were borrowed fromactive field programs. Three GPP 5.0 and three VVP 15B elec-trofishers were measured, and the data were averaged for eachmodel. Although only one ETS MBS 1D-72A and one MLESInfinity were available, each was considered representative be-cause they had recently passed their manufacturer’s inspections.The output of the GPP 5.0, VVP 15B, and ETS 1D-72A could beswitched to either high voltage for fishing in low-conductivitywaters or to low voltage for higher conductivities; the high volt-age was twice that of the low voltage. Load tests were performedfor both voltage ranges to establish the differences in their per-formance characteristics. The Infinity adjusted its voltage rangeautomatically in response to the electrical load in three distinctsteps, the switch between each step momentarily and impercep-tibly ceasing power output.

Electrical measurements were made in the absence of waterusing static loads consisting of parallel and series combinationsof 1,000-W, 57-� electric baseboard heaters (CADET model4F1000W) wired to the output of the electrofishers (Martinezand Kolz 2009). A minimum resistance (maximum electricalload) of about 5.7 � was achieved with 10 heaters connected inparallel. There is an inverse relationship between the electricalload and the power required from the electrofisher; thus, as theload resistance is decreased the power from the electrofishermust increase. By using static loads, we ensured that the electri-cal measurements were stable, repeatable, and totally removedfrom uncontrollable wave and boat motions normally encoun-tered when attempting in-water measurements (Kolz 2008; Mar-tinez and Kolz 2009). The GPP 5.0 units and the S-R generatorremained mounted in the electrofishing boat, which was parkedon its trailer. As a safety precaution, the boat hull and trailerwere electrically grounded to the soil. The other three unitswere bench-tested, the VVP 15B connected to a 220-A welderoutlet and the MBS 1D-72A and MLES Infinity powered by a6.5-kW generator. While working with the S-R VVP 15B, wemade measurements on several VVP 15 units manufactured byCoffelt Electronics. The major differences observed between thetwo models were the upgraded metering and indexed controlsoffered with the VVP 15B.

All measurements were performed at a pulse rate of 60 Hz.This frequency was tested because (1) the setting is commonly

available in commercial boat electrofishers, (2) it is recom-mended for PDC electrofishing to monitor a variety of non-salmonid, warmwater fishes (Miranda 2005; Reynolds andKolz 2013), (3) it may induce taxis of fish toward the anode(Burkhardt and Gutreuter 1995), and (4) its effects may be lessharmful to nontarget life stages or species of fish than higher fre-quencies (Holliman et al. 2003; Bohl et al. 2009; Miranda andKidwell 2010). The independent waveform controls for dutycycle offered with the VVP 15B, MBS-1D-72A, and Infinityelectrofishers were adjusted between 10% and 30% to provideadditional performance information.

The output of each boat electrofisher was measured whenconnected to the static electrical loads whose resistance was pro-gressively decreased, thereby increasing the amount of powerrequired from the electrofisher and its power source. For eachload, the voltage control on the boat electrofisher was incre-mentally increased to its maximum, and the peak voltage andcurrent recorded for calculating the corresponding peak power.As testing progressed, an electrofisher would eventually becomepower-limited, as evidenced by a reduction in its maximum out-put voltage or the audible power strain from the generator. Thetesting of an electrofisher was terminated with a particular loadwhen the unit malfunctioned either by its failure to generatea stable waveform or by the activation of its protective circuitbreakers. Although each electrofisher was intentionally adjustedto produce maximum power, there were no catastrophic failuresof any components.

Power transfer into fish.—Electrical theory predicts that, toproduce a consistent threshold of immobilization in fish, it isnecessary to adjust the applied electrode power from the elec-trofisher in a manner that is determined by the effective conduc-tivity of the fish (δf) and the ambient conductivity of the water(δw). Based on this principle (Kolz 1989; Miranda and Dolan2003), the minimum threshold of power (Pmin) required to catchfish occurs when the water conductivity is equal to that of thefish. Empirical tests have measured the effective conductivityof fish to be 90–150 µS/cm (Kolz and Reynolds 1989; Mirandaand Dolan 2003; Miranda 2009), but it is not known if fishconductivity is the same for all species of freshwater fish (Kolz2006). While this potential deviation in the conductivity of fishfunctionally makes little difference in the calculation of appliedelectrode power levels adjusted for differing ambient water con-ductivities (described as “target power” by Miranda 2009), theanalyses herein utilized 115 µS/cm (δf) as the nominal value forfish conductivity (Miranda and Dolan 2003). The applied elec-trode power that is required when the conductivities of the fishand water are not equal (target power = Pt) can be expressed asa multiplier for sustaining constant power (Mcp) transferred invivo to the fish:

Mcp = Pt/Pmin = (δw + δ f )2/4δw · δ f . (2)

Based on standardized electrofishing boat designs using a ca-thodic hull and two anodes (dropper arrays or spheres), the

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EVALUATION OF FOUR BOAT ELECTROFISHERS 35

minimum threshold of peak power for water conductivities of100–150 µS/cm ranged from 2.7 to 3.25 kW (Burkhardt andGutreuter 1995; Martinez and Kolz 2009; Miranda 2009). Inour investigation, for the two spherical anodes, we used theminimum threshold power level of 3 kW for an ambient wa-ter conductivity of 115 µS/cm, as recommended by Miranda(2009). This 3-kW recommendation would be excessive for theelectrode configuration of the electrofishing rafts, because onlya single spherical anode is powered. Therefore, a power analysiswas performed to ensure that the single anode on the raft oper-ated with the same electrical current as the individual anodes onthe boat at an ambient water conductivity of 115 µS/cm. Thiscorrection reduced the minimum threshold power level for therafts to 1.84 kW. Operators of boat electrofishers are advised thatthese minimum threshold power levels for boats (3 kW) or rafts(1.84 kW) may not initially result in successful electrofishing.The determination of power goals should be performed empir-ically for individual boats under local habitat conditions. Thisneed to identify the capture threshold for the fish communitybeing sampled is discussed further below.

Graphical presentation of data.—It is convenient to use log-arithmic graphs to plot and analyze the operating characteristicsof electrofishers (Kolz 2008). In doing so, the normalized func-tion for the multiplier for constant power (Mcp) generates asymmetric “U” shaped curve depicting the need for increasedpower (as the mismatch between water and fish conductivityincreases) when superimposed on power graphs depicting itsrelationship to water conductivity and output power (Kolz andReynolds 1989; Reynolds 1996; Miranda and Dolan 2003). Theposition of the “U” curve on logarithmic power graphs (Kolzand Reynolds 1989; Kolz 2008) can be identified by measure-ments of the power, voltage, or current associated with em-pirical observations of fish immobilization (subjectively under-stood by experienced electrofishing personnel working in situ;Reynolds 1996; Miranda and Dolan 2003; Reynolds and Kolz2013). While we have recommended minimum threshold powerlevels (Pmin) of 3 kW for boats and 1.84 kW for rafts when fishand ambient water conductivity are matched at 115 µS/cm, it isthe operators of the electrofishing equipment who provide thedata for refining these power levels by identifying the requiredpower for the desired fish response (i.e., stun, electrotaxis, nar-cosis, etc.) under field conditions. Refining these initial powerlevels helps to identify optimum electrofisher settings and mayresult in a slightly adjusted threshold power (Pmin) and reposi-tioning of the Mcp curve on the power graphs.

RESULTS

Water Conductivity versus Electrode ResistanceThe equivalent electrode resistances (R1) measured at

745 µS/cm (δ1) were 10.2 � for the boat and 25.0 � for theraft. Normalized to 100 µS/cm (δ2) using equation (1), the cor-responding resistances (R2) were 76 � for boat and 186 � for

FIGURE 1. Relationship between measured electrode resistances for twotypes of electrofishing crafts, their respective electrode configurations, and am-bient water conductivity. Values in parentheses are electrodes resistances (Ω)for each craft measured at 745 µS/cm ambient water conductivity. The twotypes of craft include aluminum-hulled john boats (cathodic hulls with dual,half-submerged, anodic spheres) and inflatable whitewater rafts (single, half-submerged anodic sphere and dual cathodic cables). The Reference Line is thelogarithmic plot of the relationship between electrical resistance of the elec-trodes and ambient water conductivity, which has a negative linear slope (1).

raft. Equation (1) was rearranged and converted to a logarithmicrelationship for the convenience of plotting the relationship ofδ2 versus R2 as a straight line having a negative linear slope(−1 or −45◦) as demonstrated by the reference line in Figure 1.

log δ2 = − log R2 + log(δ1 × R1) (3)

This logarithmic relationship of electrode resistance (R2) forthe boat and raft for ambient water conductivities (δ2) from10 to 1,000 µS/cm is displayed in Figure 1,which was createdwithout calculations by simply drawing straight lines parallel tothe reference line through the coordinates (R1, δ1) as measuredindividually for the boat and raft. Figure 1 also identifies thedifferences in electrode resistance values between the boat andraft for any water conductivity. Note that portraying ambientwater conductivity on a decreasing scale facilitates extrapolatingresistances at conductivities exceeding 1,000 µS/cm. The utilityof this logarithmic portrayal becomes apparent when placed injuxtaposition with the performance data acquired during thisstudy and depicted in power graphs.

Boat Electrofisher Performance Versus Threshold PowerAppropriately positioning the resistance-conductivity rela-

tionship for boat or rafts from Figure 1 below the correspondingboat electrofisher power charts in Figure 2 (boats) and Figure 3(rafts) illustrates how equivalent electrode resistance dictatesthe horizontal position of Pmin. Aligning the resistance axis ofFigure 1 with that of the power chart in a combined graphic

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36 MARTINEZ AND KOLZ

FIGURE 2. Measured and predicted operational characteristics for four boat electrofishers in relation to the target power level indicated by the multiplierfor constant power (Mcp) curve. The electrofishing system was cathodic aluminum-hulled john boats with dual 23-cm diameter hemispheric anodes. Each boatelectrofishers was operated at 60 Hz and at different duty cycles (%) in variable levels of ambient water conductivity simulated with static loads: (a) Smith-RootGPP 5.0 = 18%, (b) Smith-Root VVP 15B = 10%, (c) ETS MBS 1D with 72-A high-output current option = 20%, and (d) MLES Infinity = 30%.

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EVALUATION OF FOUR BOAT ELECTROFISHERS 37

FIGURE 3. Measured and predicted operational characteristics for four boat electrofishers in relation to the target power level indicated by the multiplier forconstant power (Mcp) curve. The electrofishing system used was whitewater electrofishing rafts with a single 23-cm diameter hemispheric anode and dual trailingcable cathodes. Each electrofisher operated at 60 Hz and at different duty cycles (%) in variable levels of ambient water conductivity simulated with static loads:(a) Smith-Root GPP 5.0 = 18%, (b) Smith-Root VVP 15B = 10%, (c) ETS MBS 1D with 72-A high-output current option = 20%, and (d) MLES Infinity = 30%.

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allows incorporation of water conductivity as a fifth interactiveparameter. At 115 µS/cm (i.e., equal fish and water conductivi-ties), corresponding electrode resistances are 66 � for the boatand 162 � for the raft. Thus, the coordinates for Pmin become66 � and 3 kW (boat; Figure 2), and 162 �, 1.8 kW (raft; Fig-ure 3), respectively. The applied voltage and current requiredto meet the minimum threshold power (Pmin) for a water con-ductivity of 115 µS/cm can be estimated at the points wherethey intersect the Mcp curves, as described in Figure 4: boats =445 V and 6.7 A (Figure 2), rafts = 540 V and 3.3 A (Figure 3).If desired, the applied volts (AV) and amps (AA) necessary toproduce any level of power (P) can be calculated by the twoforms of the power equation:

P = AV 2/R,

orP = AA2 × R.

(4)

The power and resistance/conductivity charts in Figures 2 and 3can be used with any value of electrode resistance and its corre-sponding water conductivity to create an Mcp curve for estimat-ing applied power, voltage, and current necessary to conformto the power transfer theory. It should be noted that, withoutelectrode resistance measurements, it would not be possible todetermine the horizontal coordinate for Pmin at 115 µS/cm, andthe nadir and resulting position of the “U” curve would onlybe known to be somewhere on the 3-kW ordinate for boat or1.8-kW ordinate for raft. This implies that calculated powertables, per se, are incomplete without identifying a correspond-ing electrode resistance.

Electrofisher Operating CharacteristicsThe high and low voltage selections of the VVP, GPP,

and MBS electrofishers produced two traces plotted from themeasured values of peak voltage in each of the four-parameterpower charts for boats (Figure 2a–c) and rafts (Figure 3a–c).The Infinity produced a single trace for its uniquely designed,automatic voltage range shifts for three ranges of voltage (Fig-ures 2d, 3d). Although only measurements of peak voltage wererequired to produce these traces, the power charts are designedto provide the corresponding values of peak power and peak cur-rent without further calculations (Kolz 2008). These operatingtraces are fixed by the electrofisher’s circuitry and cannot be al-tered by changing the configuration (shape, size, or number) ofthe anodes and cathodes of an electrofishing boat or raft. Thus,these traces represent the inherent operating characteristics ofeach electrofisher model.

The GPP 5.0 has selectable outputs of 500 and 1,000 V, butthe measured voltages for both settings were slightly higher(Figures 2a, 3a). The 1,000-V setting is necessary for elec-trofishing in low-conductivity water (Martinez and Kolz 2009)at power levels of less than 10 kW and electrode resistancesgreater than about 50 � (values extrapolated from Figures 2a,3a). With electrical loads of less than 50 �, the GPP 5.0 contin-ues to operate at the 1,000-V setting, but there can be significantvoltage degradation, indicated by excessive generator loading orinstability of the waveform near maximum load (oscilloscopedisplay) that may not be detected by the equipment operatorbecause the GPP lacks a voltmeter (Pope et al. 2001; Martinezand Kolz 2009). Consequently, we recommend that use of the1,000-V setting be avoided when operating in water where theelectrode resistance may be less than 50 � (Table 1). This is

TABLE 1. Approximate maximum power output (AMPO) measured for four commercially manufactured boat electrofishers using half-submerged 23-cmspherical anodes (two for the boat and one for the raft). High and low approximations of electrode resistances correspond to the ranges of ambient waterconductivity over which each electrofisher would be projected to provide satisfactory electrofishing performance at both of its voltage settings (note that the MLESInfinity automatically adjusts voltage in three increments). Approximate operational conductivity ranges were extrapolated from the power output measurementsplotted in Figures 2 and 3 for each electrofisher, according to the position of the multiplier for constant power (Mcp) curve.

Boat (cathodic hull) Raft (two cable-array cathodes)

Operational OperationalElectrode conductivity Electrode conductivity

Voltage resistance (Ω) range (µS/cm) resistance (Ω) range (µS/cm)Electrofisher AMPO selectormodel (kW) setting High Low Low High High Low Low High

GPP 5.0 19 500 100 6 70 1,200 180 6 100 3,0001,000 260 >50 a 28 150 500 >50a 38 370

VVP 15B 6.5 300 19 14 380 550 None None None None600 105 50 70 140 200 50 90 370

MBS 1D (72 amp) 20 300 21 3 360 2,400 20 6 900 3,000600 110 12 70 700 200 12 90 1,700

MLES Infinity 11 300, 600,and 1,100

270 7 25 1,000 500 7 36 2,500

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EVALUATION OF FOUR BOAT ELECTROFISHERS 39

FIGURE 4. Method for positioning minimum threshold power levels in Figures 2 and 3 for known electrical resistances of electrofishing boats (about 66 Ω) orrafts (about 162 Ω) at 115 µS/cm (conductivity of fish) and identifying and refining target power levels (kW) for electrofishing under local conditions of ambientwater conductivity (µS/cm) and selecting boat electrofisher settings using multiplier for constant power curves (Mcp).

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40 MARTINEZ AND KOLZ

not viewed as a serious limitation because the characteristics ofthe 500-V setting are adequate for electrofishing with electroderesistances between 6 and 50 � (i.e., higher ambient water con-ductivities). The GPP 5.0 sustained a maximum duty cycle ofabout 18% at 60 Hz when adjusted to its maximum power out-put (Figures 2a, 3a). Because the GPP 5.0 is not designed withindependent voltage and duty cycle controls (Pope et al. 2001;Miranda and Spencer 2005; Martinez and Kolz 2009), furtherexperimentation with these variables was not performed. Themaximum power available with the GPP 5.0 was about 19 kW,and an extrapolated operating range for ambient conductivitieswas about 28–1,200 µS/cm for boats and 38–3,000 µS/cm forrafts (Table 1).

The output voltages for the VVP 15B and MBS 1D-72A elec-trofishers (Figures 2b–c, 3b–c) did not deviate appreciably fromtheir selectable voltage options (300 or 600 V) as the electricalload was increased. The measured power characteristics of theCoffelt VVP 15 compared favorably with those of the S-R VVP15B, and functionally they are essentially identical. The plotsfor the VVP 15B and MBS 1D-72A voltage selections terminateabruptly at that the power level where the electrofisher’s protec-tive circuit breakers are activated for shutdown. The maximumpeak power for the VVP 15B was about 6.5 kW and the peakpower of the MBS 1D-72A approached 20 kW. These powerlimits were the same for either voltage selection: 300 or 600 V(Figures 2b–c, 3b–c). Due to its lower peak power output, theVVP 15B was unable to support a stable PDC waveform thatexceeded a 10% duty cycle (Figures 2b, 3b). The higher poweroutput of the MBS 1D-72A sustained a stable PDC waveformat 20% duty cycle (Figures 2c, 3c). The projected 20-kW ratingfor the MBS 1D-72A was extrapolated from the 300-V data(dashed line on graph) because we were unable to overload thisboat electrofisher with our lowest load resistance of 5.7 ohms.The manufacturer advised that the MBS 1D equipped with the72-A option is capable of powering a 3- � load (personal com-munications, B. O’Neal, ETS, LLC). The extrapolated oper-ating ranges for ambient conductivity for the VVP 15B wereabout 70–550 µS/cm for boats and 90–370 µS/cm for rafts(Table 1). For the MBS 1D-72A, these operating ranges wereabout 70–2,400 µS/cm for boats and 90–3,000 µS/cm for rafts(Table 1).

The power traces for the MLES Infinity (Figures 2d, 3d)did not conform to fixed voltage settings as the load resistancewas decreased because the electrofisher is designed with controlcircuitry that automatically limits its maximum output to about11 kW at discrete, maximum output voltages of about 300,600, and just over 1,100 V (Figures 2d, 3d). Compared with theother three electrofishers, the MLES Infinity demonstrated threecycles of maximum output power occurring at those values ofelectrical resistance where the unit automatically switched itsvoltage range in response to decreasing resistance and increasingpower demand. The MLES Infinity sustained stable PDC poweroutput for both boats and rafts at a duty cycle of 30% (Figures 2d,3d). The extrapolated operating ranges for ambient conductivity

for the MLES Infinity were about 25–1,000 µS/cm for boats and36–2,500 µS/cm for rafts (Table 1).

DISCUSSION

Electrode Resistance and ConfigurationThis study validates the importance of electrode resistance,

which ultimately dictates the operational performance of elec-trofishers (Dean and Temple 2011). In fact, the effectiveness ofan electrofisher can be enhanced or degraded within a particularrange of water conductivity by the configuration of the selectedelectrodes. Operators and manufacturers of electrofishing equip-ment have experimented with a variety of electrode designs, butelectrode resistance has seldom been acknowledged as a sig-nificant variable (Reynolds and Kolz 2013). It is only when themeasured characteristics of the electrofishers are complementedby the effects of electrode resistance that this relationship be-comes apparent.

The optimum design of an electrode array is not limited tomeasurements of its resistance; the characteristics of the in-water electrical field must also be considered. This combinationof variables needs to be explored for possible improvements inelectrode configuration, and the measurement techniques pro-vided by Kolz (1993), Beaumont et al. (2006), and Miranda andKratochvı́l (2008) are considered to be applicable. The pairedspherical anodes (half-submerged) used with the boat in thisstudy differed from the ring and cylindrical dropper anode ar-rays described for the standard boat proposed by Miranda andBoxrucker (2009). While the electrode resistance for the boat inMiranda and Boxrucker (2009) was not specified, a resistanceof about 60 � (at 115 µS/cm) was estimated from its tabu-lated values of power and current (Miranda 2009). This 6- �

difference (60 � versus 66 �) between these two standardizedelectrode configurations is graphically inconsequential. Thus,Figure 2 can be considered to represent the performance of theelectrofishers tested in this study with either of these electrodeconfigurations.

This similarity does not imply that the two boats would fishthe same even with the same applied power coming from iden-tical electrofishers and using the same electrical waveform set-tings (Miranda 2005). The spatial and heterogeneous, in-waterelectrical variables (voltage gradient, current density, and powerdensity) are determined by the size, shape, and configuration ofthe electrodes, and the cylindrical droppers will create a more in-tense voltage gradient field than that of the 23-cm hemispheres.We predict that, if the anode spacing is the same for these twoboats, the recommended power threshold of 3 kW at 115 µS/cmwould probably require at least some correction for one of theseboats. Field personnel should anticipate that it will require mul-tiple fish-response threshold observations in different valuesof water conductivity before determining the most acceptablepower correction (Mcp) for their particular electrode array. Whileexperimental laboratory observations have contributed to iden-tifying power thresholds (Kolz and Reynolds 1989; Dolan and

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EVALUATION OF FOUR BOAT ELECTROFISHERS 41

Miranda 2003; Miranda and Dolan 2003; Miranda 2005), thereare no theoretical methods currently available for avoiding thissubjective approach.

Performance Evaluations for the Four Boat ElectrofishersOur evaluations of the four boat electrofishers were con-

ducted at a frequency of 60 Hz. It would require a substantialamount of additional time to record data for several frequen-cies and duty cycles. However, the development of meaningfulspecifications for electrofishers is the responsibility of the man-ufacturers, and this task should not be imposed on the limitedresources of electrofishing operators. Further, the equipmentspecifications presently offered by manufacturers of electrofish-ers typically do not provide adequate explanations regarding theperformance capabilities of these power supplies when operat-ing with different electrical loads.

For years, field personnel have been frustrated by the un-certainty in adjusting settings on their electrofishers. Equip-ment operators desire to know the range of water conductivi-ties in which they can expect to successfully electrofish. Thiswould be preferable to determining this limitation by trial-and-failure after having invested in a particular electrofisher thatmay not adequately power their electrode configuration underthe prevailing conditions in the local habitats they sample. Thepeak voltage measurements recorded by this study along withknown values of static loads resolves this enigma by creatinggraphic presentations that serve as handy references for fieldpersonnel.

Our findings for boat electrofisher performance, when usedwith the electrode configurations described in this study, arereadily applicable for users of similar electrofishing craft byinterpreting the power outputs for boats (Figure 2) or rafts (Fig-ure 3). The position of the Mcp function on each power chartindicates the power, voltage, and current required for any givenelectrical load or water conductivity based upon the initial min-imum threshold power levels of 3 kW for boats or 1.8 kW forrafts at matched ambient water and effective fish conductivities(115 µS/cm). When the output measured for an electrofisher(voltage, current, or power) exceeds the theoretical Mcp require-ment, the electrofisher can be successfully operated; otherwise,the electrofisher performance will probably prove inadequate.Accordingly, surplus output from an electrofisher can be re-duced to the desired level, closer to the Mcp function, but itis impossible to artificially generate additional output with aninadequate electrofisher or power source.

Table 1 provides predicted operational capabilities for eachboat electrofisher based upon those segments of their operatingtraces in Figures 2 and 3 that exceed the power requirementsof the Mcp function for the boat or raft. The electrode resis-tance and water conductivity values were extrapolated from thegraphs and did not require any calculations. This simplicity ininterpretation can be observed using Figures 2b and 3b to revealthat the VVP 15B probably offers inadequate operational capa-bility with the 300-V setting for electrofishing operations using

23-cm hemispherical anodes. In this case, the electrofisher sim-ply lacks the output power necessary to support the electricalload. These examples verify the significance of electrode resis-tance in determining the success or failure of an electrofisher’soperation.

Operators of electrofishing equipment are reminded that thehorizontal position of the power transfer function (Mcp), and theelectrode resistance can be altered at their discretion by chang-ing the configuration of the electrode array. As illustrated by thisstudy, the applied power and electrode resistance differences be-tween the boat and raft resulted in electrofishing systems withdivergent operational capabilities. Analyses of these systemsdemonstrate the unique association of electrofishing principlesby displaying the power transfer function (Mcp), the electroderesistance measurements (δw versus R), and the measured vari-ables for the electrofishers (P versus R) on a single graphic.

Variations Due to Operational and Conductivity FactorsThe electrode and boat electrofisher measurements con-

ducted during this study were performed under ideal, stable con-ditions, but field personnel cannot always expect to encounterthese near-laboratory situations. In practice, normal operationalvariability associated with lateral and vertical movements aselectrofishing boats and rafts are maneuvered, fluctuations inwater depth, distance between electrodes, surface wave action,and relative electrode submergence are uncontrolled, electroderesistance variables. These resistance variations will, in turn,affect the output of the electrofisher, suggesting that the appliedelectrode power will be a dynamic range around the target powerlevel that must fluctuate to account for these changes in the activeelectrical field (Kolz 2008; Miranda 2009). Thus, the precisionof the electrode resistance lines in Figure 1 must be consideredan oversimplification, and a more realistic presentation shouldbe viewed as a statistical variance relative to the mean.

The inverse relationship between electrode resistance andwater conductivity obviously contributes to the limitation ofelectrofisher performance based on its design parameters andpower source. While Table 1 indicates operational capacity forsome boat electrofishers above 2,000 µS/cm, electrofishing maybecome less efficient at extremely high conductivities (1,000–3,000 µS/cm; Speas et al. 2004). As power demand at higherwater conductivity climbs as electrode resistance decreases,electrical waveforms may not conform to control settings ormay display instability (Van Zee et al. 1996; Martinez and Kolz2009). Under the latter conditions, the power transfer theory andMcp curve are no longer valid because the theory requires con-sistent waveforms at all power levels. However, some studiesreport that there may be no significant effects of conductiv-ity less than about 1,500 µS/cm on catchability or electrofishingefficiency (Hill and Willis 1994; Dumont and Dennis 1997; Bay-ley and Austen 2002). Further, increasing electrode resistanceby using single anodes may allow electrofishing at high conduc-tivities, as indicated for rafts in Table 1, even for power-limited

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electrofishers such as the VVP 15 (Hill and Willis 1994; VanZee et al. 1996).

Significance of Duty CycleMiranda and Dolan (2004) reported that duty cycles of 10–

50% require the least peak power to immobilize fish, provide thehighest margin between the power levels that narcotized versustetanized fishes, and allowed a larger radius of immobilizationaway from the anode. This range of intermediate duty cycles isconsidered to be less injurious to warmwater fishes (Dolan andMiranda 2004; Miranda and Dolan 2004). Further, duty cyclesof 20–30% are associated with electrotaxis of fishes (Burnet1959; Habera et al. 2010), which tends to facilitate fish cap-ture (Novotny and Priegel 1974; Burkhardt and Gutreuter 1995;Maret et al. 2007); however, conclusive laboratory or field testshave not been performed.

The GPP 5.0 can be adjusted to increase applied power withinthe first half of its voltage control (Percent of Range knob), butit lacks an independent control for duty cycle (Miranda andSpencer 2005). As its power output begins to plateau at a fre-quency setting of 60 Hz, a duty cycle of about 18% is achieved(Martinez and Kolz 2009). This potential limitation in promotingelectrotaxis with the GPP 5.0 may be overcome by electrofish-ing at 120 Hz, whereby the voltage control within the first halfof its adjustment includes duty cycles exceeding 20% (Martinezand Kolz 2009). While duty cycle can be adjusted on the VVP15B, its power limitation restricted our tests to 10% duty cycle,which would not be expected to elicit electrotaxis. However,field observations suggest that at lower ambient water conduc-tivities around 100–200 µS/cm, a duty cycle of about 20% maybe sustained with VVP-15 units (Hall 1986), facilitating elec-trotaxis and fish capture (C. Walford, Larval Fish Laboratory,Colorado State University, personal communication).

InstrumentationThe availability of accurate electrical meters on electrofishers

is an important feature for monitoring power output and elec-trofishing performance (Dean and Temple 2011). It was not theintent of this study to evaluate the meters supplied with the boatelectrofishers; however, boat electrofishers deserving recogni-tion for being designed with accurate peak voltage and peakcurrent meters include the ETS MBS 1D (Miranda 2009) andthe MLES Infinity. Peak reading meters provide the advantageof applying the precepts of constant power transfer by using ei-ther peak voltage or current measurements as indices of poweroutput or by using these values to calculate peak power. TheVVP 15B is instrumented with a peak voltmeter that providedonly marginal scale resolution (Coffelt VVP 15 meters are notpeak-reading; Van Zee et al. 1996), and the GPP current me-ter is considered too inaccurate for standardized measurements(Pope et al. 2001, Miranda and Spencer 2005; Martinez andKolz 2009).

Recommendations to overcome metering deficiencies ofsome boat electrofisher models have included portable oscil-

loscopes (Miranda and Spencer 2005); scopemeters, i.e., Fluke123 with 80i–110 s current clamp (Miranda 2009) and Fluke 97(Dean and Temple 2011); peak-reading digital multimeters, i.e.,Fluke 87V with i200 AC clamp (L. Kolz) and Fluke 87V (Deanand Temple 2011); and computer software (i.e., S-R Power Stan-dardization System). Measurement of peak current offers the ad-vantage of higher resolution and a linear relationship with waterconductivity (Miranda 2009). For water conductivities greaterthan the fish conductivity (e.g., >115 µS/cm), it is suggestedthat peak current should be considered the preferred measure-ment to assess electrofishing performance and conformance totarget power levels for maintaining constant transfer of in vivopower.

SUMMARY COMMENTSIndependent measurements of electrode resistance and boat

electrofisher power output characteristics were combined in thisstudy to create a graphic analysis technique that incorporates theelectrofishing principles asserted by power-transfer theory (Kolz1989; Miranda and Dolan 2003; Reynolds and Kolz 2013). Thisinclusive visual approach simultaneously establishes the rela-tionship between the variation of resistance for any electrodearray and the required electrofishing power, as well as betweenthe voltage and current at any measured value of ambient wa-ter conductivity. These analyses can be performed graphicallywithout reference tables or manual calculations.

Our study contributes to the recent emphasis for standardiz-ing fish sampling using electrofishing (Martinez and Kolz 2009;Miranda 2009; Reynolds and Kolz 2013). It is suggested thatthe equipment measurements performed in this study be seri-ously considered as part of the development of protocols forstandardized electrofishing. This information should improvethe understanding of the role of electrode resistance in dictatingpower demand from electrofishers. It should also aid selectionof a boat electrofisher model based on its capacity to sustainstandardized power levels in accordance with the system resis-tance of the electrofishing craft in which they are used and overthe range of water conductivities encountered.

ACKNOWLEDGMENTSThis work would not have been possible without the equip-

ment, assistance, and cooperation provided by Anita Martinez,Lori Martin, and Estevan Vigil of the Colorado Parks andWildlife and Bob Burdick and Michael Gross at the U. S. Fishand Wildlife Service in Grand Junction, Colorado. We thankAngela Kantola of the Upper Colorado River Endangered FishRecovery Program and the National Fish and Wildlife Founda-tion for their financial support. Burke O’Neal (ETS Electrofish-ing, LLC) and Tom Lehman (Midwest Lake Management, Inc.)graciously provided loans for the boat electrofishers used in ourevaluation. Reference to trade names does not imply endorse-ment of commercial products by the federal government.

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EVALUATION OF FOUR BOAT ELECTROFISHERS 43

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