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Electrofishing is a common scientific survey method used to sample fish populations to determine abundance, density and species composition. When performed correctly, electrofishing results in no permanent harm to the fish, which return to their natural mobility state in as little as two minutes after being caught.[1]
Method
Electrofishing relies on two electrodes which deliver direct current at high-voltage from the anode to the cathode through the water.[2] When a fish encounters a large enough potential gradient on this path, it becomes affected by the electricity. Usually pulsed direct current (DC) is applied, which causes galvanotaxis in the fish. Galvanotaxis is uncontrolled muscular convulsion that results in the fish swimming towards the anode. Teams of at least two people are recommended for an effective electrofishing crew: one to operate the anode, and the other to catch the stunned fish with a dip net.
Types
Electrofishing by boat
There are three types of electrofishers: backpack models, tote barge models, and boat mounted models, sometimes called a stunboat.[2]
Backpack electrofisher generators are either battery or gasoline powered. They employ a transformer to pulse the current before it is delivered into the water. The anode is located at the end of a long, twometer pole and is usually in the form of a ring. The cathode is a long, three-meter braided steel cable that trails behind the operator. The electrofisher is operated by a deadman's switch on the anode pole. There are a number of safety features built into newer backpack models, such as audible speakers that sound when the unit is operating, tilt-switches that incapacitate the electrofisher if the backpack is tilted more than 45 degrees, and quick-release straps to enable the user to quickly remove the electrofisher in the event of some emergency.
When boat electrofishing, the boat itself is the cathode, and the anode(s) are generally mounted off the bow.[2] The stunned fish swim toward the anode, where they are caught alive using a dip net.[3] Towed barge electrofishers operate similarly to backpack electrofishers, with the exception that the generator is located on a floating barge instead of on a backpack. Often the barge can be left stationary on the shore and longer cathodes and anodes allow the crew to sample large areas. Barge electrofishers often employ gas-powered generators since a user does not have to carry the extra weight on his or her back.
A method of electrofishing using illegally diverted electricity from overhead electric lines is prevalent in parts of the Indian State of Kerala. This can result in accidental deaths due to electrocution.[4]
Effectiveness
The effectiveness of electrofishing is influenced by a variety of biological, technical, logistical, and environmental factors. The catch is often selectively biased as to fish size and species composition. When using pulsed DC for fishing, the pulse rate and the intensity of the electric field strongly influence the size and nature of the catch. The conductivity of the water influences the shape and extent of the electric field and thus affects the field's ability to induce capture-prone behavior in the fish.
It can also cause injury to the fish. The electricity causes muscle spasms that damage the vertebrae. For unknown reasons,[5] this is more common and severe in longer fish.[6]
Due to the conductivity of saltwater, electrofishing is not an effective tool for catching saltwater fish, as the electricity travels through the water, rather than through the fish.[7]
Legality
While electrofishing is used by multiple government agencies, it may be illegal to use it as a form of recreational fishing. This method can be considered poaching. For example, in Florida, as in many other states, it is illegal for recreational use.[7]
Electrofishing is potentially dangerous, or even lethal.[9] The high voltages and currents used, compounded with the presence of water, present serious safety risks. The typical dangers of electrocution, such as electrically induced unconsciousness and the paralysis of the heart and lungs,[10] are compounded by the risk of drowning, which may result from the aforementioned hazards. In light of this, many safety precautions are taken for those handling electrofishing equipment and those nearby.[2][7][11]
↑ 2003 study: Immobilization Thresholds of Electrofishing Relative to Fish Size, biologists Chad Dolan and Steve Miranda
↑ Steven R. Dalbey; Thomas E. McMahon; Wade Fredenberg (1 August 1996). "Effect of Electrofishing Pulse Shape and Electrofishing-Induced Spinal Injury on Long-Term Growth and Survival of Wild Rainbow Trout". North American Journal of Fisheries Management. 16 (3): 560–569. doi:10.1577/1548-8675(1996)016<0560:eoepsa>2.3.co;2. S2CID35356334.
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically-conducting phase between electrodes separated by an ionically conducting and electronically insulating electrolyte.
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit. Electrodes are essential parts of batteries that can consist of a variety of materials depending on the type of battery.
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.
The cavity magnetron is a high-power vacuum tube used in early radar systems and subsequently in microwave ovens and in linear particle accelerators. A cavity magnetron generates microwaves using the interaction of a stream of electrons with a magnetic field, while moving past a series of cavity resonators, which are small, open cavities in a metal block. Electrons pass by the cavities and cause microwaves to oscillate within, similar to the functioning of a whistle producing a tone when excited by an air stream blown past its opening. The resonant frequency of the arrangement is determined by the cavities' physical dimensions. Unlike other vacuum tubes, such as a klystron or a traveling-wave tube (TWT), the magnetron cannot function as an amplifier for increasing the intensity of an applied microwave signal; the magnetron serves solely as an electronic oscillator generating a microwave signal from direct current electricity supplied to the vacuum tube.
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential. The word "lysis" means to separate or break, so in terms, electrolysis would mean "breakdown via electricity".
Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current. The part to be coated acts as the cathode of an electrolytic cell; the electrolyte is a solution of a salt of the metal to be coated; and the anode is usually either a block of that metal, or of some inert conductive material. The current is provided by an external power supply.
An electrical injury, or electrical shock is damage sustained to the skin or internal organs on direct contact with an electric current.
An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. A solid, liquid, or gel electrolyte covers the surface of this oxide layer, serving as the cathode or negative plate of the capacitor. Because of their very thin dielectric oxide layer and enlarged anode surface, electrolytic capacitors have a much higher capacitance-voltage (CV) product per unit volume than ceramic capacitors or film capacitors, and so can have large capacitance values. There are three families of electrolytic capacitor: aluminium electrolytic capacitors, tantalum electrolytic capacitors, and niobium electrolytic capacitors.
A thyratron is a type of gas-filled tube used as a high-power electrical switch and controlled rectifier. Thyratrons can handle much greater currents than similar hard-vacuum tubes. Electron multiplication occurs when the gas becomes ionized, producing a phenomenon known as Townsend discharge. Gases used include mercury vapor, xenon, neon, and hydrogen. Unlike a vacuum tube (valve), a thyratron cannot be used to amplify signals linearly.
Erotic electrostimulation is a sexual practice involving the application of electrical stimulation to the nerves of the body, with particular emphasis on the genitals, using a power source for purposes of sexual stimulation. Electrostimulation has been associated with BDSM activities, and erotic electrostimulation is an evolution of that practice.
High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, high voltage refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant special safety requirements and procedures.
Zinc–air batteries (non-rechargeable), and zinc–air fuel cells are metal–air batteries powered by oxidizing zinc with oxygen from the air. These batteries have high energy densities and are relatively inexpensive to produce. Sizes range from very small button cells for hearing aids, larger batteries used in film cameras that previously used mercury batteries, to very large batteries used for electric vehicle propulsion and grid-scale energy storage.
Snagging, also known as snag fishing, snatching, snatch fishing, jagging (Australia), or foul hooking, is a fishing technique for catching fish that uses sharp grappling hooks tethered to a fishing line to externally pierce into the flesh of nearby fish, without needing the fish to swallow any hook with its mouth like in angling. This is achieved by suddenly and vigorously pulling the line when movement is felt, causing the snag hook to "claw" into any fish unfortunate enough to be grappled by the hook points. Weighted multi-hook rigs can be used to increase chances of success, and modern technologies such as underwater video camera can also be used to visually aid and time the snagging.
Douglas Dam is a hydroelectric dam on the French Broad River in Sevier County, Tennessee, in the southeastern United States. The dam is operated by the Tennessee Valley Authority (TVA), which built the dam in record time in the early 1940s to meet emergency energy demands at the height of World War II. Douglas Dam is a straight reinforced concrete gravity-type dam 1705 feet long and 202 feet high, impounding the 28,420-acre (11,500 ha) Douglas Lake. The dam was named for Douglas Bluff, a cliff overlooking the dam site prior to construction.
Fishing techniques are methods for catching fish. The term may also be applied to methods for catching other aquatic animals such as molluscs and edible marine invertebrates.
A solid oxide electrolyzer cell (SOEC) is a solid oxide fuel cell that runs in regenerative mode to achieve the electrolysis of water by using a solid oxide, or ceramic, electrolyte to produce hydrogen gas and oxygen. The production of pure hydrogen is compelling because it is a clean fuel that can be stored, making it a potential alternative to batteries, methane, and other energy sources. Electrolysis is currently the most promising method of hydrogen production from water due to high efficiency of conversion and relatively low required energy input when compared to thermochemical and photocatalytic methods.
Electrodeionization (EDI) is a water treatment technology that utilizes DC power, ion exchange membranes, and ion exchange resin to deionize water. EDI is typically employed as a polishing treatment following reverse osmosis (RO). It differs from other RO polishing methods, like chemically regenerated mixed beds, by operating continuously without chemical regeneration.
Electric pulse fishing is a fishing technique sometimes used in trawl fisheries which produces a limited electric field above the seabed to catch fish. The pulse trawl gear consists of a number of electrodes, attached to the gear in the tow direction, that emit short electric pulses. The electrodes replace the tickler chains that are used in traditional beam trawl fishery. The pulse trawl fishery is mainly aimed at flatfish like sole, with by-catch plaice. In addition, the pulse trawl gear is applied in shrimp fisheries on a limited scale. Technically, the use of electricity to catch fish is prohibited in European waters. However, the European Union is able to provide exemptions to this rule since 2007. These exemptions are now mainly used by Dutch and British trawlers in the North Sea.
Aluminum electrolytic capacitors are polarized electrolytic capacitors whose anode electrode (+) is made of a pure aluminum foil with an etched surface. The aluminum forms a very thin insulating layer of aluminum oxide by anodization that acts as the dielectric of the capacitor. A non-solid electrolyte covers the rough surface of the oxide layer, serving in principle as the second electrode (cathode) (-) of the capacitor. A second aluminum foil called “cathode foil” contacts the electrolyte and serves as the electrical connection to the negative terminal of the capacitor.
Electric fishing can refer to one of two methods of fishing:
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