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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.
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.
A vacuum tube, electron tube, valve, or tube is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
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.
A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. In comparison with other commercial rechargeable batteries, Li-ion batteries are characterized by higher specific energy, higher energy density, higher energy efficiency, a longer cycle life, and a longer calendar life. Also noteworthy is a dramatic improvement in lithium-ion battery properties after their market introduction in 1991: over the following 30 years, their volumetric energy density increased threefold while their cost dropped tenfold.
An electrical injury, or electrical shock is damage sustained to the skin or internal organs on direct contact with an electric current.
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 a 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.
Asian carp is a grouping of fishes commonly used to mean silver, bighead carp, white and black amur, which are regarded invasive in the United States. These four species, also known as copi, are native to China where they are collectively known as qing cao lian yong (青草鲢鳙) or si da jia yu and are farmed for food.
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.
Gibbons Creek Reservoir is a power plant cooling reservoir on Gibbons Creek in the Navasota River basin, 20 miles (32 km) east of College Station, Texas, United States. The dam and lake are managed by Texas Municipal Power Agency (TMPA), which uses the reservoir as a cooling pond for a coal-fired power plant generating electricity for the cities of Bryan, Denton, Garland, and Greenville.
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.
Aluminium–air batteries produce electricity from the reaction of oxygen in the air with aluminium. They have one of the highest energy densities of all batteries, but they are not widely used because of problems with high anode cost and byproduct removal when using traditional electrolytes. This has restricted their use to mainly military applications. However, an electric vehicle with aluminium batteries has the potential for up to eight times the range of a lithium-ion battery with a significantly lower total weight.
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.
Electrolysed water is produced by the electrolysis of ordinary tap water containing dissolved sodium chloride. The electrolysis of such salt solutions produces a solution of hypochlorous acid and sodium hydroxide. The resulting water can be used as a disinfectant.
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.
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 (usually) 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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