Fish Schools - Furuno CH-250 Operator's Manual

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: 0˚ to 10˚
(B) Midwater, bottom fish
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.
Sea surface
reflections
Tilt angle: 30˚ or more
Figure 2-22 Fish schools
Fish
school
Bottom
Fish
school
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.
Fish
school
Large midwater
fish school is
present.
Bottom
2-25