Fish finding sonar systems assist spearos when trying to locate and identify fish. These sonar units operate in a very certain way. A transducer, attached to a boat, sends out an acoustic signal. This signal will reflect off the swim bladder of the fish which corresponds to a specific acoustic impedance.
Because the air bladder contains gas, it is a drastically different density than the flesh and bones of the fish, as well as the water that surrounds it. The amount of gas in the air bladder can be increased or decreased to regulate the buoyancy of the fish. This difference in density causes the sound waves from the echosounder to bounce off the fish distinctively. The transducer receives the echoes and this is exactly how the fish finder is able to recognize these differences. The fish finder then displays it as a fish. The images of the fish on the screen of the echosounder appear as arches because of the movement of the fish through the beam of acoustic energy.
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