The electrofisher is such an electronic device by the means of which a man may - at certain practice - catch fishes in large quantities and very quickly. Idea of the electrofisher is based on a fact that at the flow of electric direct current in water appears at fishes so-called anode reaction (galvanotaxis) under influence of which fish begins to flow from negative electrodes to positive electrodes. Most interesting is fact, that the greater the fish the more with pleasure she goes out from water in direction of the landing net.
Drawing below presents behaviour of the fish under influence of electric current.
Anode reaction of the fish (pulling in direction of anode) is explained by this, that fish catches definite direction of movement of ions and directs oneself with head on their stream. Under influence of electric field brawn of fishes shrink and it raises automatically. Truth is, that to anodes it can not reach if around anode voltage is higher from critical. In such case fish falls in state of nervous shock and sails out or drops on the bottom. To prevent it the voltage enlarges or diminishes with distance between cathode and anode. This, however, represents certain technical difficulties. Enlargement of space between electrodes with attempt of keeping optimum electric field causes enlargement of dangerous zone for fish. Apart from that parameters of applied electric field in considerable degree depend on conductivity of waters (saltiness), temperatures, from surface of electrodes, source of power supply. There are lots sorts of fishes, they differ between themselves by size. After researches it was found that it takes place only in case of direct current or impulse current. Most effective appears direct current, however, it is partially limited to use only to freshwaters of low-conductivity waters. In most salty waters it would demand usage of large power in power supply of such devices. As a result most of cases it is used impulse current. Impulse current is more efficient at smaller energy necessary to power supply the electrofisher.
Basic part of electrofishing is catching fish for reproduction, nevertheless, one can use it equally well to fish in consumer aims. Equipped in such a device a fisherman may press the button of steering, to dip electrodes and to "pick up" hypnotised fishes. In moment of hunting swim up fishes of different sizes, little ones after shaking down oneself from nervous shock sail away in several seconds hiding at random, larger ones are chosen by fisherman.
During the flow of electric current in water with sufficient power fish raises from minus to plus. This reaction is called anode reaction. All art in this so that electric current was direct current. However to receive power of direct current necessary to embrace sufficient zones of water no battery would not be sufficiently large. Because of that we use impulse current. One should know, that for every fishes it is necessary to choose own parameters of impulses. Some corrections carries in many factors as: weather, time of year, property of a given waters, biological state of fishes and others. Hunting on fishes on electric current is at present times modern art. Electrofisher should meet many conditions and requirements in order to catch well and about this below.
Not going excessively into theory one should say, so that to catch fish well electrofisher should meet the following criteria:
1. Electrofisher should be maximum strong for a given battery (accumulator) - allowing this - we may enlarge zone of fishing. However, we should not forget, that fish has to swim up freely to landing net at optimum circumstances of fishing and in such manner not to hurt the fish and if it is necessary to release it (little fish, fry).
2. We should know, that in water it is important to ensure the flow of electric current (Amperes) and not voltage ( Volt).
3. Surface of electrodes should be possibly maximum in reasonable extent, to enlarge the flow of current and freely to operate them. Cathode should be a piece of 1, 5-2 metre of flexible copper line of thickness about 2 mm.
4. Intensity of impulses should be minimum - and in given time to give to waters suitable power.
5. Frequency of impulses should be regulated in range from 5 to 120 Hz.
6. Length of impulses should be in range circa 30 microseconds - 3 milliseconds. In case of smaller frequency wider impulse (length).
7. Electrofisher should properly work in range of resistivity from 20 to 500 ohms.
8. From battery we can courageously take current in amperes equal its capacity in Ah (Ampere-hours).