Raymarine L470 instruction manual Fish Indications, Operating Instructions, kHz 200 kHz

Fish Indications

Even using advanced sonar technology, it is sometimes hard to detect a fish in the water. The body of a fish is just a little more dense than the surrounding water. There is really nothing very solid for the sound waves to bounce off of. The FishFinder L470 is very good at telling the difference between a fish and the surrounding water. In fact, Raymarine is the leader in this technology.

When the FishFinder detects a fish, it can be indicated by a fish symbol on the display. In general, a larger symbol means a larger fish. This rule is not always true, though. Let’s say that there are two fish of the same size: one is close to the surface, and the other is near the bottom. The fish which is close to the surface will have a larger symbol. This is because the fish which is closer returns more of the sound waves back to the FishFinder.

Actually, the sound waves are usually reflected by the air sac near the center of the fish, and not by the body of the fish. The size of this air sac is different for different kinds of fish. This can also affect the size of the

50 kHz

200 kHz

An arch-shaped image indicates a fish.

The same fish appears differently when shown by the 50 kHz or 200 kHz transducer beams.

This indicates a group of small fish.

This shows a fish detected in sidelooker mode.

A shallow arch or horizontal line is generated when the boat is moving slowly or stopped.

When the boat is moving very fast,

a fish appears as a single vertical line.

Fig. 3-5

Fish Indications

38 Operating Instructions