Furuno CSH-84 - Manual (Page 84)

11-2
Fish Schools
A fish school appears as a mass of echoes on the screen. The
color of the mass shows the density of fish schools on the sonar
beam. To find distribution and center point of a fish school, try
several different tilt angles.
(A) Sea surface fish
Tilt angle: -5° to 10°
(B) Midwater, bottom fish Tilt angle: 30° or more
Fish echo which appears before seabed can be detected.
Tilt angle: -0° to 20°
Fish echo which appears together with
or after seabed can be detected.
Seabed
Fish
school
Sea surface
reflections
Fish
school
Seabed echo not
displayed because
of narrow tilt angle.
Sea surface
reflections are
present.
Fish
school
Large midwater
fish school is
present.
Seabed
When the tilt angle is shallow,
the reflection echo from seabed
is weak and the fish echo
which appears from bottom
is easy to find.
Figure 11-2 Fish schools