Presentation on theme: "Introduction to Electrofishing"— Presentation transcript:
1 Introduction to Electrofishing Lisa HarlanSmith-Root, Inc.
2 Outline Electrical Theory Electrofishing Equipment Operation and SafetyApplied Electrofishing MethodsWritten Exam
3 “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.
4 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.
5 “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?
6 What is electricity? The presence or movement of free electrons. Protons, electrons, and ionsElectrofishing is concerned with electrons and ions.
7 Current “Free electrons” - flow easily from one ion to another. 6.3 x 1018 electrons/sec = 1 AmpAmperes or Amps - flow of electric current.
9 Conductors, Insulators, Semi-conductors, cont. Insulators - Substances with very few free electrons, flow of electrons is slow and arduous.RubberDry airGlassFiber-reinforced plasticsDistilled water
10 Conductors, Insulators, Semi-conductors, cont. Semi-conductors - Substances that are in-between conductors and insulators.SiliconSea waterRain waterCity waterGermaniumSilicon and Germanium used in diodes and transistors.
11 Why is this important?You need to know where the electricity will flow and where it won’t flow.
12 Basic Electrical Theory Amperage - current, flow of free electronsVoltage - electrical pressureResistance - amount of blockage or drag resisting the currentConductivity - the inverse of resistance
13 Ohm’s Law Calculates for Current (Amps). Voltage = Current / ConductivityCurrent = Conductivity * VoltageConductivity = Current / VoltageNote* Conductivity is the inverse of resistance. Ohms Law is V=I*R“Conductivity” is measured in uS. “Specific Conductivity” is measured in uS/cm.
14 Watt’s Law Calculates for Power (watts). Power (watts) = Voltage * Currentand Ohm’s Law statesCurrent = Voltage * ConductivitythereforePower = Voltage * Voltage * Conductivity(AMP). A unit of electrical current or the rate of flow of electrons through a conductor. One volt across one ohm of resistance causes a current flow of one ampere. One ampere equals 6.25 x 1018 electrons per second passing a given point in a circuit; abbreviated amp. For example, a 1,200 watt, 120-volt hair dryer pulls 10 amps of electric current (watts divided by volts).
15 Main Components of the Electrofisher Power SourceControl UnitElectrodes
20 Voltage The amplitude (or height) of the waveform. Measured in volts. E.g. 120V
21 Types of Electrical Waveforms ACDCPulsed DCBurst of PulsesPros and ConsCatches a lot of fishEasy to produceLow power lossHigh level of injuryCatches fewer fishEasy to produceHigh power requirementLow level of injuryCatches many fishHard to produceMod. power requirementIntermediate level of injuryCatches many fishHard to produceLow power requirementIndications are low level of injury
22 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.
23 Frequency The number of pulse periods per second (hertz or Hz.). The inverse of pulse period.1/pulse period
24 Pulse WidthThe duration of “on” time within one pulse period.
25 % Duty Cycle The percentage of “on” time within one pulse period. Pulse WidthPulse Period* 100% = % Duty CycleNote* Frequency & Percent Duty Cycle has more effect on fish behavior AND fish injury.So use of minimal settings and proper technique is paramount.20 ms40 ms* 100% =50% Duty Cycle
26 How do these things affect fish ? Standard Pulse WaveformDEFINITIONSPulse width :The length of timethe current is ONperiodwidthFrequency :Number of pulsesin a secondvoltsHow do these things affect fish ?time
27 a b 1 3 5 Exploring the Effects on Fish NOTE: volts The shorter Pulse width :The length of timethe current is ONThe shorterthe on-time,the less poweryou put intothe water andinto the fishNOTE:voltsb135Time (ms)
28 a b 1 3 5 Exploring the Effects on Fish NOTE: volts The fewer the Frequency (Hz):Number of pulsesper secondaThe fewer thepulses, thebetter.Frequency isa major factorin fish injury !!NOTE:voltsb135Time (ms)
29 To minimize fish injury: use lowest pulse width and frequency Time (ms)513onoff
31 Duty-cycle = “pulse width” X “pulse frequency” (divided by 10) Example:Pulse width = 4 msFrequency = 20 HzDuty-cycle = (4 x 20)/10 = 8%
32 Duty-cycle = (4 x 20)/10 = 8% Duty-cycle = 24% Pulse width = 4 ms Frequency = 20 HzPulse widthFrequencyDuty-cycle = (4 x 20)/10 = 8%Duty-cycle = 24%
33 Electric Field Intense near electrodes Dissipates with distance Reynolds, 1996
34 Power Density Power Density = Voltage Gradient * Current Density Power = Voltage * Voltage * Conductivity*Note voltage gradient (v/cm) and current density (A/cm2) as well as water conductivity (uS/cm). V/cm*A/cm2= watts/cm3.Sort of combining of Ohm’s Law and Watt’s Law Based on Volume.*Note quadrupling effect on Power Density when voltage is doubled.
36 Conductivity of Water Low Conductivity < 100 S/cm Requires higher voltage.High conductivity > 1, S/cmRequires 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.
37 Power Transfer TheoryUse “behavior” of electrical current to explain this interaction.Reynolds, 1996
38 Review How do changes in water conductivity affect power requirements? How do changes in fish conductivity affect power requirements?
39 Electrofishing Equipment There are a variety of electrofishers systems out there…
45 Function of Control Units Accepts input from power sourceControls and allows control of the outputInstrumentation monitors input and outputHas power on/power off controlHas connectors for anode and cathodeTimers to measure electrofishing time
46 2.5, 5.0, 7.5, 9.0 GPP ElectrofishersProduces 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.
47 VVP - 15B Electrofisher Produces DC, pulsed DC and AC. Pulsed DC- Freq Hz, Duty cycle 10-80%.Burst of Pulses - groups of 3 or 6 at Hz.AC - 60 Hz.Will Service Coffelt Products Except MK-10 & MK-18 (backpack shockers)MK-50-B (Boat/Shore unit)
48 LR-24 Electrofisher Produces DC, pulsed DC, and Burst of Pulses. Pulsed DC - Freq Hz, Duty cycle %.Burst of Pulses Hz
49 Electrodes - Backpack and Shore-based AnodesCathodes
53 Cathode SizeThe cathode should have ~3 times the surface area as the anode.The larger surface area decreases the electric field intensity near the cathode.
54 Electrode ShapeThe electric field is affected by the shape of the electrode.Show examples on white board.(Ask Rick)
55 Electrode ConditionElectrolysis 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.Stainless steel will eventually rust due to the fact that the nickel content gets “zapped” out of it from electricity being run though it (aka: electrolysis).
56 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.
57 Four Behavioral Zones Fright Zone Taxis Zone Tetanus Zone Kill Zone Note that not all “zones” are equally spaced away from anode. Site specific changes in electric field (voltage, electrode issues, conductivity, fish orientation, etc.).
58 Fish Behavior Definitions Fright/Escape: fish swim awayTaxis: Fish swims toward anodeTetany/Narcosis: fish immobilizedKill
59 Like a puppet on a a string! This is taxis.Lead fish to netters.Increase efficiency.Decrease injuryReady to net that fish… No.
60 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?
61 Potential Fish Injuries Stress SyndromeHemorrhagingVertebral InjuryDeathEgg Viability and Reproductivity
62 Stress Syndrome Physiological and behavioral changes Acidosis and reduced respiratory efficiencyCan take hours to days to recoverIf death occurs, it’s usually within a few hours, and is respiratory failure.
63 Fish Hemorrhaging Level Two Level Three Represents ONE actual hemorrhage.Level Three
64 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.
66 Injuries to FishFisheries Techniques, Chp 8 Slideshow
67 Death of Fish Egg Viability and Reproductivity 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 ReproductivityNot much is known about the effects of electrofishing in this area. Avoid spawning females and active spawning areas.
68 Factors that Affect Fish Injury 1. Settings on the Electrofisher2. Equipment Choices3. Electrofishing Technique
69 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)
70 Conductivity of Water Low Conductivity < 100 S/cm Requires higher voltage.High conductivity > 1, S/cmRequires 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.
71 Types of Electrical Waveforms ACDCPulsed DCBurst of PulsesPros and ConsCatches a lot of fishEasy to produceLow power lossHigh level of injuryCatches fewer fishEasy to produceHigh power requirementLow level of injuryCatches many fishHard to produceMod. power requirementIntermediate level of injuryCatches many fishHard to produceLow power requirementIndications are low level of injury
72 “What Settings Should I Use?” Use the lowest voltage, frequency, and duty cycle combination that elicits “taxis” but minimizes “tetanus”.
73 If fish twitches and escapes, voltage is high enough! Step 1: VoltsNeed enough voltsto get fishto twitch.If fish twitches and escapes,voltage is high enough!USFS,Boise ID
74 power density quadruples. A note about voltage….Power density = (Volts/cm)2 x conductivityIf you double voltage,power density quadruples.
76 Vertebral Injury DataUnpublished Data: Do Not Cite
77 Behavior and Vertebral Damage (Frequency) Unpublished Data: Do Not Cite
78 % of Marked Fish Showing Vertebral Damage Unpublished Data; Do Not Cite
79 Equipment ChoicesElectrodes: size, shape, condition, orientationDip Nets: shape, depth and mesh sizeElectrofisher: appropriate one for the conditions
80 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!”
81 Electrofishing Technique, cont. What would you change?Resist “pointing” with anode.Reduce exposure.Site variables?“Hey! That was my fish!”
82 What would you change? Safety first. Water level/velocity. Position of netters.Differences in netting techniques.Levels of efficiency.How deep is still safe?
83 Care of FishRemove 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.
84 “What should I do if I observe fish with external marking?” First, evaluate your technique.Make adjustments accordingly.Second, evaluate your settings.Reduce frequency.Reduce duty cycle.Reduce voltage.
85 Review 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?
86 “Why Should I Bother With Safety?” All electrofishers have enough power to kill humans.
87 Effects of Electrical Current on the Human Body 1 milliampJust a faint tingle.5 milliampsSlight shock felt. Disturbing, but not painful. Most people can “let go”. However, strong involuntary movements can cause injuries.6-25 milliamps (women)9-30 milliamps (men)Painful shock. Muscular control is lost. This is the range where “freezing currents” start. It may not be possible to “let go”.milliampsExtremely painful shock, respiratory arrest (breathing stops), severe muscle contractions. Flexor muscles may cause holding on; extensor muscles may cause intense pushing away. Death is possible.1,000-4,300 milliamps( amps)Ventricular fibrillation (heart pumping action not rhythmic) occurs. Muscles contract; nerve damage occurs. Death is likely.10,000 milliamps(10 amps)Cardiac arrest and severe burns occur. Death is probable.*Effects are for voltages less than about 600 volts. Higher voltages also cause severe burns.*Differences in muscle and fat content affect severity of shock.Centers for Disease Control and Prevention, 2002
93 Additional Backpack Electrofisher Safety Features Immersion SensorElectrode Out of Water SensorVisual Signal (Red Flashing Light)
94 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.
95 Crew PreparationMaintain 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.
96 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.
97 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.
98 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.
99 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.
100 Operational SafetyNever 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.
101 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.
102 Crew Safety Accidents happen Be prepared for the worst Safety equipmentSafety procedures
103 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.
104 Review What are the responsibilities of the crew leader? How do you electrofish safely?
105 Applied Electrofishing Determine sampling parameters prior to electrofishing:ObjectivesAmount of effort - distance, time, or sample size.“Consistency and objectivity”
107 Standardized sampling guidelines Collect all fish possible to avoid biasStandardize voltage outputPulse rate = 5-40 HzDuty cycle = 25%Standardize season - spring or fallStandardize the water stage in flowing water (not too high or low)Fisheries Techniques,Chp 8 slideshow
108 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.
109 Data analysis Species composition Species abundance Population structurePopulation dynamics - catch curve/mark-recaptureSpecies composition- will be successful with certain species,but not all. Watch for bias.Species abundance- CPUE very good when targeting specific age classes.Population structure - Length-frequency data should be regarded with caution. Electrofishing is size selective.Population dynamics - Very limited possibilites due to size selectivity of electrofishing.
110 Review Electrical Theory Electrofishing Equipment Operation and Safety Applied Electrofishing Methods
111 SourcesDepartment of Health and Human Services. Electrical Safety: Safety and Health for Electrical TradesReynolds, James. Electrofishing. Pages B. R. Murphy and D. W. Willis, editors. Fisheries techniques, 2nd edition. American Fisheries Society, Bethesda, MD
112 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.