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Introduction to Electrofishing. Lisa Harlan Smith-Root, Inc. Outline. Electrical Theory Electrofishing Equipment Operation and Safety Applied Electrofishing Methods Written Exam. “What is electrofishing?”. The use of electricity to capture, guide, and block the movement of fish.

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introduction to electrofishing

Introduction to Electrofishing

Lisa Harlan

Smith-Root, Inc.

  • Electrical Theory
  • Electrofishing Equipment
  • Operation and Safety
  • Applied Electrofishing Methods
  • Written Exam
what is electrofishing
“What is electrofishing?”
  • The use of electricity to capture, guide, and block the movement of fish.
  • An effective biological sampling tool.
  • When done correctly injury to fish is minimal.
  • This requires knowledge.
history of electrofishing
History of Electrofishing
  • Started in the late nineteenth century.
  • Became fishery science tool in 1950’s and 60’s.
  • Technology and knowledge have improved over the years.
  • There are still many unknowns.
why is it important to be knowledgeable
“Why is it Important to be Knowledgeable?”
  • Electrofishers have enough power to kill you.
    • How many people have been shocked before?
  • Electrofishers have enough power to kill fish.
    • How many people have seen injured fish before?
what is electricity
What is electricity?
  • The presence or movement of free electrons.
  • Protons, electrons, and ions
  • Electrofishing is concerned with electrons and ions.

“Free electrons” - flow easily from one ion to another.

6.3 x 1018 electrons/sec = 1 Amp

Amperes or Amps - flow of electric current.

conductors insulators semi conductors
Conductors, Insulators, Semi-conductors
  • Conductors - Lots of free electrons
      • Metals, particularly
      • Copper
      • Stainless Steel
      • Aluminum
conductors insulators semi conductors cont
Conductors, Insulators, Semi-conductors, cont.
  • Insulators - Substances with very few free electrons, flow of electrons is slow and arduous.
      • Rubber
      • Dry air
      • Glass
      • Fiber-reinforced plastics
      • Distilled water
conductors insulators semi conductors cont10
Conductors, Insulators, Semi-conductors, cont.
  • Semi-conductors - Substances that are in-between conductors and insulators.
      • Silicon
      • Sea water
      • Rain water
      • City water
      • Germanium
    • Silicon and Germanium used in diodes and transistors.
why is this important
Why is this important?

You need to know where the electricity will flow and where it won’t flow.

basic electrical theory
Basic Electrical Theory

Amperage - current, flow of free electrons

Voltage - electrical pressure

Resistance - amount of blockage or drag resisting the current

Conductivity - the inverse of resistance

ohm s law calculates for current amps
Ohm’s LawCalculates for Current (Amps).

Voltage = Current / Conductivity

Current = Conductivity * Voltage

Conductivity = Current / Voltage

watt s law calculates for power watts
Watt’s LawCalculates for Power (watts).

Power (watts) = Voltage * Current

and Ohm’s Law states

Current = Voltage * Conductivity


Power = Voltage * Voltage * Conductivity

main components of the electrofisher
Main Components of the Electrofisher
  • Power Source
  • Control Unit
  • Electrodes
control units
Control Units



power sources





Power Sources
  • The amplitude (or height) of the waveform.
  • Measured in volts.
    • E.g. 120V
types of electrical waveforms
Types of Electrical Waveforms



Pulsed DC

Burst of Pulses

Pros and Cons

  • Catches many fish
  • Hard to produce
  • Low power requirement
  • Indications are low level of injury
  • Catches a lot of fish
  • Easy to produce
  • Low power loss
  • High level of injury
  • Catches fewer fish
  • Easy to produce
  • High power requirement
  • Low level of injury
  • Catches many fish
  • Hard to produce
  • Mod. power requirement
  • Intermediate level of injury
pulse period
Pulse Period
  • The duration of time for one complete cycle.
  • A cycle is measured from the start of one pulse to the start of the next pulse.
  • Measurement includes both “on” and “off” times.
  • The number of pulse periods per second (hertz or Hz.).
  • The inverse of pulse period.
    • 1/pulse period
pulse width
Pulse Width
  • The duration of “on” time within one pulse period.
duty cycle
% Duty Cycle

Pulse Width

Pulse Period

* 100% = % Duty Cycle

20 ms

40 ms

* 100% =

The percentage of “on” time within one pulse period.

50% Duty Cycle


How do these things affect fish ?

Standard Pulse Waveform


Pulse width :

The length of time

the current is ON



Frequency :

Number of pulses

in a second





The shorter

the on-time,

the less power

you put into

the water and

into the fish

Exploring the Effects on Fish


Pulse width :

The length of time

the current is ON






Time (ms)



The fewerthe

pulses, the


Frequency is

a major factor

in fish injury !!

Exploring the Effects on Fish

Frequency (Hz):

Number of pulses

per second







Time (ms)









Time (ms)

To minimize fish injury:

use lowest

pulse width and frequency


“Duty-cycle” is the

percent of on-time

duty cycle pulse width x pulse frequency divided by 10
Duty-cycle = “pulse width” X “pulse frequency” (divided by 10)


Pulse width = 4 ms

Frequency = 20 Hz

Duty-cycle = (4 x 20)/10 = 8%


Pulse width = 4 ms

Frequency = 20 Hz

Pulse width


Duty-cycle = (4 x 20)/10 = 8%

Duty-cycle = 24%

electric field
Electric Field
  • Intense near electrodes
  • Dissipates with distance

Reynolds, 1996

power density
Power Density

Power Density = Voltage Gradient * Current Density

Power = Voltage * Voltage * Conductivity

conductivity of water
Conductivity of Water

Low Conductivity < 100 S/cm

Requires higher voltage.

High conductivity > 1,500 - 2000 S/cm

Requires high current.

  • Power requirement lessens as the conductivity of the water matches the conductivity of the fish.
  • Conductivity of the water and fish increase as temperature increases.
power transfer theory
Power Transfer Theory

Reynolds, 1996

  • How do changes in water conductivity affect power requirements?
  • How do changes in fish conductivity affect power requirements?
electrofishing equipment
Electrofishing Equipment

There are a variety of electrofishers systems out there…

main components of the electrofishing system
Main Components of the Electrofishing System
  • Control Unit
  • Power Source
  • Electrodes
power sources44
Power Sources



function of control units
Function of Control Units
  • Accepts input from power source
  • Controls and allows control of the output
  • Instrumentation monitors input and output
  • Has power on/power off control
  • Has connectors for anode and cathode
  • Timers to measure electrofishing time
2 5 5 0 7 5 9 0 gpp electrofishers
2.5, 5.0, 7.5, 9.0 GPP Electrofishers

Produces pulsed forms of AC and DC.

AC at 60Hz, DC at 7.5, 15, 30, 60 and 120 Hz.

Control of pulse width and frequency on DC.

vvp 15b electrofisher
VVP - 15B Electrofisher

Produces DC, pulsed DC and AC.

Pulsed DC- Freq 5 - 120Hz, Duty cycle 10-80%.

Burst of Pulses - groups of 3 or 6 at 15 - 120 Hz.

AC - 60 Hz.

lr 24 electrofisher
LR-24 Electrofisher

Produces DC, pulsed DC, and Burst of Pulses.

Pulsed DC - Freq 1 - 120Hz, Duty cycle 1 - 99%.

Burst of Pulses - 1 - 1000Hz

important electrode parameters
Important Electrode Parameters
  • Size
  • Shape
  • Condition
  • Orientation
anode size
Anode Size

Reynolds, 1996

cathode size
Cathode Size
  • The cathode should have ~3 times the surface area as the anode.
  • The larger surface area decreases the electric field intensity near the cathode.
electrode shape
Electrode Shape

The electric field is affected by the shape of the electrode.

electrode condition
Electrode Condition
  • Electrolysis of the aluminum occurs over time creating a hard ceramic insulating surface.
  • Aluminum electrodes need to be cleaned regularly.
  • Netting impedes cleaning (and…).
  • Stainless steel electrodes do not oxidize.
electrode orientation
Electrode Orientation
  • The electric field is affected by the position of the electrodes in relation to each other.
  • The closer they are together the more intense the field.
four behavioral zones
Four Behavioral Zones
  • Fright Zone
  • Taxis Zone
  • Tetanus Zone
  • Kill Zone
fish behavior definitions
Fish Behavior Definitions
  • Fright/Escape: fish swim away
  • Taxis: Fish swims toward anode
  • Tetany/Narcosis: fish immobilized
  • Kill
like a puppet on a a string
Like a puppet on a a string!
  • This is taxis.
  • Lead fish to netters.
  • Increase efficiency.
  • Decrease injury
  • Ready to net that fish… No.
fish injury
Fish Injury
  • What are the potential injuries to fish?
  • How can I tell if fish are being injured?
  • What can I do to reduce fish injury?
potential fish injuries
Potential Fish Injuries
  • Stress Syndrome
  • Hemorrhaging
  • Vertebral Injury
  • Death
  • Egg Viability and Reproductivity
stress syndrome
Stress Syndrome
  • Physiological and behavioral changes
    • Acidosis and reduced respiratory efficiency
  • Can take hours to days to recover
  • If death occurs, it’s usually within a few hours, and is respiratory failure.
fish hemorrhaging
Fish Hemorrhaging

Level Two

Level Three

external branding
External “Branding”
  • Caused by capillaries under skin hemorrhaging.
  • Usually chevron-shaped.
  • Can be long-lasting and be a site for infection.
  • Likely has internal injuries as well.
  • Unbruised fish might also have internal injuries.
  • Dark splotches can appear which are not bruising and will disappear in a short time.
injuries to fish
Injuries to Fish

Fisheries Techniques, Chp 8 Slideshow


Death of Fish

Consider filleting dead fish to look for hemorrhaging. Fillet along both sides of spine, looking for bloody spots near spine corresponding to spots on fillet.

Egg Viability and Reproductivity

Not much is known about the effects of electrofishing in this area. Avoid spawning females and active spawning areas.

factors that affect fish injury
Factors that Affect Fish Injury

1. Settings on the Electrofisher

2. Equipment Choices

3. Electrofishing Technique

setting up the electrofisher
Setting Up the Electrofisher
  • Know conductivity of the water.
  • Select a waveform.
  • Set a voltage.
  • Select a frequency.
  • Select the pulse width (or duty cycle)
conductivity of water70
Conductivity of Water

Low Conductivity < 100 S/cm

Requires higher voltage.

High conductivity > 1,500 - 2000 S/cm

Requires high current.

  • Power requirement lessens as the conductivity of the water matches the conductivity of the fish.
  • Conductivity of the water and fish increase as temperature increases.
types of electrical waveforms71
Types of Electrical Waveforms



Pulsed DC

Burst of Pulses

Pros and Cons

  • Catches many fish
  • Hard to produce
  • Low power requirement
  • Indications are low level of injury
  • Catches a lot of fish
  • Easy to produce
  • Low power loss
  • High level of injury
  • Catches fewer fish
  • Easy to produce
  • High power requirement
  • Low level of injury
  • Catches many fish
  • Hard to produce
  • Mod. power requirement
  • Intermediate level of injury
what settings should i use
“What Settings Should I Use?”

Use the lowest voltage, frequency, and duty cycle combination that elicits “taxis” but minimizes “tetanus”.


Step 1: Volts

Need enough volts

to get fish

to twitch.

If fish twitches and escapes,

voltage is high enough!



A note about voltage….

Power density = (Volts/cm)2 x conductivity

If you double voltage,

power density quadruples.

hemorrhage data
Hemorrhage Data

Unpublished Data: Do Not Cite

vertebral injury data
Vertebral Injury Data

Unpublished Data: Do Not Cite

behavior and vertebral damage frequency
Behavior and Vertebral Damage (Frequency)

Unpublished Data: Do Not Cite

of marked fish showing vertebral damage
% of Marked Fish Showing Vertebral Damage

Unpublished Data; Do Not Cite

equipment choices
Equipment Choices
  • Electrodes: size, shape, condition, orientation
  • Dip Nets: shape, depth and mesh size
  • Electrofisher:appropriate one for the conditions
electrofishing technique
Electrofishing Technique
  • Minimize fish exposure time to electric field.
  • Keep distance between electrode & fish consistent (if possible).
  • Be quick about netting the fish.

“Hey Buddy! Don’t break a sweat!”

electrofishing technique cont
Electrofishing Technique, cont.
  • What would you change?
  • Resist “pointing” with anode.
  • Reduce exposure.
  • Site variables?

“Hey! That was my fish!”

what would you change
What would you change?
  • Safety first.
  • Water level/velocity.
  • Position of netters.
  • Differences in netting techniques.
  • Levels of efficiency.
  • How deep is still safe?
care of fish
Care of Fish
  • Remove fish immediately from electrical field and into holding buckets.
  • Avoid netting rocks also.
  • Refresh water frequently or use an aerator.
  • Work up fish often.
  • If holding fish in netted area make sure they are always out of electrical field after capture.
what should i do if i observe fish with external marking
“What should I do if I observe fish with external marking?”
  • First, evaluate your technique.
    • Make adjustments accordingly.
  • Second, evaluate your settings.
    • Make adjustments accordingly.
      • Reduce frequency.
      • Reduce duty cycle.
      • Reduce voltage.
  • List the 3 main components of an electrofisher.
  • How does electrode size affect the electric field?
  • What are the potential injuries to fish?
  • How should you set up an electrofisher?
why should i bother with safety
“Why Should I Bother With Safety?”

All electrofishers have enough power to kill humans.

effects of electrical current on the human body
Effects of Electrical Current on the Human Body

Centers for Disease Control and Prevention, 2002

life threatening condition
Life-threatening Condition
  • Cardiac Arrest
  • Ventricular Fibrillation
  • Respiratory Arrest
  • Lactic Acidosis (delayed onset)
how do i electrofish safely
“How Do I Electrofish Safely?”
  • Training
  • Proper Equipment
  • Crew Preparation
  • Emergency Planning
  • Operational Safety
  • Minimum of two crew members trained in First Aid/CPR particularly as applied to electric shock.
  • Crew leader, at a minimum, has taken an Electrofishing Course.
proper equipment personal protection equipment
Proper Equipment - Personal Protection Equipment


  • Non-breathable Waders or Hip Boots.
  • Non-slip Boots
  • Lineman’s Gloves


  • PFD or Wading Belt
  • Brimmed Hat
  • Polarized Sunglasses
proper equipment backpack electrofisher
Proper Equipment - Backpack Electrofisher
  • Tilt Switch
  • Anode Pole (Power Output) Switch
  • Audible Signal
  • Quick Release Harness
  • Emergency Kill Switch
additional backpack electrofisher safety features
Additional Backpack Electrofisher Safety Features
  • Immersion Sensor
  • Electrode Out of Water Sensor
  • Visual Signal (Red Flashing Light)
proper equipment fully functional
Proper Equipment - Fully Functional
  • Inspect equipment before every use. Don’t work with faulty or malfunctioning electrofishing equipment.
    • Damaged curl cord.
    • Damaged connectors.
    • Broken anode pole switch.
    • Damage strain relief (top of pole).
    • Dead/broken battery or out of gas.
crew preparation
Crew Preparation
  • Maintain a crew size of at least 3 preferably 4 people (at least 4 people for shore-based electrofishers).
  • Have an assigned crew leader.
  • Clarify crew leader responsibilities.
  • Clarify crew responsibilities.
crew preparation crew leader responsibilities
Crew Preparation - Crew Leader Responsibilities
  • Ensure overall crew safety, meet sampling objectives, and monitor welfare of the fish.
    • Brief all crew on basics of electrofishing, including dangers and safety requirements.
    • Have emergency plan in place and communicate it to all crew members.
      • Nearest hospital and quickest route to it.
      • Location of vehicle keys, cell phones, radios and how to operate them.
    • Crew leader is only person to order power on.
    • Ensure all crew knows anyone can order power off.
crew preparation crew responsibilities
Crew Preparation - Crew Responsibilities
  • Be trained in basics of electrofishing and safe electrofishing practices.
  • Be aware of nearest hospital, evacuation route, location of vehicle keys, cell phones, and radios and know how to operate them.
  • Be alert and attentive, take breaks as necessary.
  • Communicate with rest of crew.
  • Do not electrofish if you have heart ailments, wear a pacemaker, or are pregnant.
crew preparation crew communication
Crew Preparation - Crew Communication
  • Effective communication between crew members is essential.
  • Be sure you know the plan before the electrodes are energized.
  • If working in noisy conditions utilize hand signals.

Standardized “Power On” and “Power Off” Signals.

      • Power On: Patting hand on top of head with announcement.
      • Power Off: Slicing the hand across the throat with announcement.
      • Hand signals and announcements confirmed by everyone.
emergency planning
Emergency Planning
  • Prepare and have a plan ahead of time.
  • Always carry First Aid kit.
  • In case of accident:
    • Turn off power to electrofisher and remove it from the situation.
    • Evaluate situation and take appropriate action.
    • If a person has been shocked they need to go immediately to nearest hospital.
operational safety
Operational Safety
  • Never electrofish alone. Minimum of three person crew.
  • Remove chest strap before entering water.
  • Shut off power before entering or leaving water.
  • Be sure all crew members are clear of electrodes before turning power on and before energizing electrodes.
  • Do not touch electrodes when power is on, not even while wearing Lineman’s gloves.
  • Turn electrofisher off before connecting or replacing parts.
operational safety cont
Operational Safety, cont.
  • Operate slowly and carefully to prevent slips and falls.
  • Electrofish only as far as you can safely wade.
  • Never electrofish with spectators on shore.
  • Stop electrofishing immediately if water gets in waders, hip boots, or gloves. Do not resume electrofishing until completely dry.
crew safety
Crew Safety
  • Accidents happen
  • Be prepared for the worst
  • Safety equipment
  • Safety procedures
crew safety things to avoid
Crew Safety - Things to Avoid
  • Don’t become the conductor.
  • Don’t touch anything in the surroundings.
  • Don’t touch the electrodes.
  • Don’t use uninsulated dip net handles.
  • Don’t work without properly fitting/fully functional personal safety equipment.

What are the responsibilities of the crew leader?

How do you electrofish safely?

applied electrofishing
Applied Electrofishing
  • Determine sampling parameters prior to electrofishing:
    • Objectives
    • Amount of effort - distance, time, or sample size.
    • “Consistency and objectivity”
factors that affect sampling efficiency
Factors that affect Sampling Efficiency
  • Electrodes
  • Water/ Environmental Conditions
  • Equipment Settings/ Capabilities
  • Fish Variables
  • Human Components
standardized sampling guidelines
Standardized sampling guidelines
  • Collect all fish possible to avoid bias
  • Standardize voltage output
    • Pulse rate = 5-40 Hz
    • Duty cycle = 25%
  • Standardize season - spring or fall
  • Standardize the water stage in flowing water (not too high or low)

Fisheries Techniques,Chp 8 slideshow

lake and pond sampling
Lake and Pond Sampling
  • Use boat electrofisher.
  • Spring and autumn are when adults tend to be close to shore.
  • Night or twilight are when predators move inshore.
  • Sample entire shoreline if possible. If not, more small samples better than few large samples.
data analysis
Data analysis
  • Species composition
  • Species abundance
  • Population structure
  • Population dynamics - catch curve/mark-recapture
  • Electrical Theory
  • Electrofishing Equipment
  • Operation and Safety
  • Applied Electrofishing Methods
  • Department of Health and Human Services. Electrical Safety: Safety and Health for Electrical Trades. 2002.
  • Reynolds, James. Electrofishing. Pages 221- 253. B. R. Murphy and D. W. Willis, editors. Fisheries techniques, 2nd edition. American Fisheries Society, Bethesda, MD. 1996.
stream sampling
Stream Sampling
  • Backpack electrofishers good for small streams.
  • Shore-based or boats for larger streams.
  • Flowing waters limit sampling due to safety issues.
  • Boat-shock usually downstream, wade usually upstream.
  • Sample streams methodically with randomness.