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Introduction to Electrofishing

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

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  1. Introduction to Electrofishing Lisa Harlan Smith-Root, Inc.

  2. Outline • Electrical Theory • Electrofishing Equipment • Operation and Safety • Applied Electrofishing Methods • Written 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 ions • Electrofishing is concerned with electrons and ions.

  7. Current “Free electrons” - flow easily from one ion to another. 6.3 x 1018 electrons/sec = 1 Amp Amperes or Amps - flow of electric current.

  8. Conductors, Insulators, Semi-conductors • Conductors - Lots of free electrons • Metals, particularly • Copper • Stainless Steel • Aluminum

  9. 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

  10. 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.

  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 electrons Voltage - electrical pressure Resistance - amount of blockage or drag resisting the current Conductivity - the inverse of resistance

  13. Ohm’s LawCalculates for Current (Amps). Voltage = Current / Conductivity Current = Conductivity * Voltage Conductivity = Current / Voltage

  14. Watt’s LawCalculates for Power (watts). Power (watts) = Voltage * Current and Ohm’s Law states Current = Voltage * Conductivity therefore Power = Voltage * Voltage * Conductivity

  15. Main Components of the Electrofisher • Power Source • Control Unit • Electrodes

  16. Control Units Backpack Boat

  17. Anode Cathode Boat Electrodes

  18. Cathodes Anodes Backpack / Shore-based Electrodes

  19. Direct Current Alternating Current Power Sources

  20. Voltage • The amplitude (or height) of the waveform. • Measured in volts. • E.g. 120V

  21. Types of Electrical Waveforms AC DC 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

  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 Width • The duration of “on” time within one pulse period.

  25. % 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

  26. How do these things affect fish ? Standard Pulse Waveform DEFINITIONS Pulse width : The length of time the current is ON period width Frequency : Number of pulses in a second volts time

  27. NOTE: The shorter the on-time, the less power you put into the water and into the fish Exploring the Effects on Fish a Pulse width : The length of time the current is ON volts b 5 1 3 Time (ms)

  28. NOTE: The fewerthe pulses, the better. Frequency is a major factor in fish injury !! Exploring the Effects on Fish Frequency (Hz): Number of pulses per second a volts b 5 1 3 Time (ms)

  29. on on off off 5 1 3 Time (ms) To minimize fish injury: use lowest pulse width and frequency

  30. “Duty-cycle” is the percent of on-time

  31. Duty-cycle = “pulse width” X “pulse frequency” (divided by 10) Example: Pulse width = 4 ms Frequency = 20 Hz Duty-cycle = (4 x 20)/10 = 8%

  32. Pulse width = 4 ms Frequency = 20 Hz Pulse width Frequency Duty-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

  35. Specific Water Conductivity

  36. 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.

  37. Power Transfer Theory 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…

  40. Backpack electrofishing

  41. Tote-barge electrofishing

  42. Boat electrofishing

  43. Main Components of the Electrofishing System • Control Unit • Power Source • Electrodes

  44. Power Sources Battery Generator

  45. 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

  46. 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.

  47. 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.

  48. 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

  49. Cathodes Anodes Electrodes - Backpack and Shore-based

  50. Anode Cathode Boat Electrodes

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