Furuno FSV-85 Operator's Manual page 68

2. HORIZONTAL MODE
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.
2-42
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
which appears from bottom
is easy to find.
Bottom echo not
displayed because
of decreased tilt angle.
Sea surface
reflections are
present.
School
of fish
Large midwater
fish school is
present.
Bottom