Fishfinders

In 1490, Leonardo da Vinci wrote 'If you cause your ship to stop, and place the head of a long tube in the water and place the other side of the tube to your ear, you will hear ships at a great distance from you.' In a sense, we can say that Leonardo da Vinci created the first fishfinder. Centuries later, the idea of using an air-filled tube between the sea and the listener's ear was used in World War I. The instrument used was called a sonar. A fishfinder is a form of sonar. Sonar is an acronym for sound navigation and ranging. It consists of a transmitter, receiver, transducer, and a feedback device, which is actually a display screen. A transmitter, through the use of a transducer, converts an electrical impulse into a sound wave and sends it into the water. When the wave strikes a fish, a specific amount of the wave is reflected back, depending on the composition, size and shape of the fish. The reflected signal, which is referred to as an echo, is displayed on the screen.A fish that is swimming directly under your boat will create a consistent echo that causes a continuous line to appear on the display. A stationary fish will appear as a single point on the screen. A fish identification system assists the angler by recognizing the echo from the fish and displaying a fish icon on the screen. The icon can also tell you where the fish is in relationship to the boat. Some fishfinders come with an optional alarm that lets the angler know that a fish has been detected.