Furuno FSV-25 Operator's Manual page 71

School of fish
A school of fish appear as a mass of echoes on the screen. By this display pattern, the
density of the school on the sonar beam can be found. To find distribution and center
point of a school of fish, try several different tilt angles.
(A) Sea surface fish
Tilt angle: 0° to 10°
(B) Midwater, bottom fish Tilt angle: 30° or more
Fish echo which appears before bottom can be detected.
Tilt angle: 0° to 20°
Fish echo which appears together with
or after bottom can be detected.
School
of fish
Sea surface
reflections
Bottom
School
of fish
When the tilt angle is shallow,
the reflection echo from bottom
is weak and the fish echo that
appears from bottom is easy to find.
2. HORIZONTAL MODE
Bottom echo not
displayed because
of decreased tilt angle.
Sea surface
reflections are
present.
School of fish
Bottom echo
clearly displayed.
.
Bottom
2-41