Fishing has always been one of the most used professions by human beings and also a popular hobby. But with the evolution of man and advancement of technology, human beings have started using the modern techniques in fishing also. The technique was earlier is used only by dolphins and whales to determine if something was ahead of them. But with passing time, a human has learnt from them and used their technology against them. Dolphins and whales generated an underwater ultrasonic sound which reflected back. The impression of the reflected sound gave them the idea of what was in front of them. This principle is known as sonar and radar principle.
The technical knowledge
Now, fish moves in shoals under water. So when the sound is coming back to the radar, it gets obstructed. This will help to understand the location of the shoal. Let’s get to a detailed explanation. Fish finders are fitted with sound transducers. When dolphins have a different source of generation of sound and reception, a transducer has both the properties of both emission and detection of sound. Like the dolphin, the transducer also emits sound and receives the reflected sound. The time lag in emission and reception of sound is used to detect the underwater movement and speed of the body. This helps to calculate the distance of the objects from the ship. The transducer is also used to detect the intensity of the sound reflected. There is the difference between the quality of sound that is reflected from a shoal or a single fish and other bodies present in water.
A beam of ultrasonic sound, ranging from 20 to 200 kHz is sent. The width of the beam can be controlled by the ship. That depends on and varies with the depth or distance to which it has to be sent in order to detect the fish. The width of the beam varies the range of the sound.
Characteristic of beams of sound-
The narrower the beam of sound emission is, longer is the range. And at the same time, wider the beam is, shorter is the range. But when the beam is used for long range detection, there will be interferences. Then there is the option of displays as seen by the operator. Some fish finders just give a raw image of some moving interference. Whereas some fish finders will give a distinct symbol of the fish. Another feature which varies is the direction in which the sound beam is being sent. This depends on the depth of the seabed or the type of fish that is intended to be caught. Some fishes are deep sea fish. In that case, the sound has to be sent vertically, perpendicular to the seabed.
The sound gets reflected from the seabed, and the moving fish is used to determine the depth of the movement of the fish. The best fish finder also helps to determine the density of fish present. The fish movement is displayed on the display unit located on the board.
When going for a fish finder, you should determine first the type of fishing you wish to go for. You should also decide whether you wish to go for fishing in still water or moving water. All these conditions determine the type of fish finder that is to be used.