Fish Indications; Fig. 3-4 Fish Indications - Raymarine L750 Operating Handbook

Chapter 3: Operating Instructions
Before we explain the other basic pages, there are some general things
you should know about the operation of the Fishfinder.

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 L750 Fishfinder is very good at telling the
difference between a fish and the surrounding water.
When the Fishfinder finds a fish, it displays an arch-shaped mark. See Fig.
3-4. In general, a larger arch indicates 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
50 kHz
50 kHz

Fig. 3-4 Fish Indications

An arch-shaped image indicates a fish.
The same fish appears differently
when shown by the 50 kHz or 200 kHz
transducer beams.
200 kHz
This is how the images appear when
the "fish symbol" feature is turned on.
Notice that the depth is indicated.
200 kHz
A shallow arch is generated when
the boat is moving slowly.
This indicates a group of small fish.
This shows a fish detected in
sidelooker mode.
A fish moving under a stopped
boat shows as a line.
When the boat is moving very fast,
a fish appears as two parallel lines.
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