10. VIDEO SOUNDER OPERATION
10-27
Fish school density
If two schools appear with the same color at different depth, the one in deeper water
is denser because the ultrasonic wave attenuates as it propagates and the fish school
in deep water tends to be displayed in a weaker color.
Fish school density
Plankton
A plankton layer, a likely place to find fish, is displayed in green or blue dots. It usually
descends in the day and rises at night.
Plankton
Current rip
When two ocean currents meet with different speeds, directions and water tempera-
tures, a current rip develops. A current rip's on-screen appearance is as shown below.
Current rip
Fish echo
Less Reddish
(Sparse echo)
Reddish
(Dense echo)
Difference in
signal strength
Weak Echo
Strong
Echo
Fish
School
Plankton
Current
rip
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