Fish Indications - Raymarine L470 Instruction Manual

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
An arch-shaped image indicates a fish.
The same fish appears differently
when shown by the 50 kHz or 200 kHz
50 kHz
transducer beams.
200 kHz
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.
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Fig. 3-5
Fish
Indications
Operating Instructions