Bottom contour
For the hard rock bottom, the echoes are largely shown in reddish-brown or red with a
long tail on the screen. For the mud, gravel or algae bottom, the echo screen has less
red with a short tail. When the bottom is flat without any bottom material changes, a
bottom picture with a uniform width is shown. A longer tail appears on slopes and drop-
offs because the travel time to the bottom is different at both edges of the ultrasonic
beam. However, even when the tail is long, the visual width becomes narrower because
the picture shows a sloped bottom. For the rough bottom, echoes are reflected on many
different planes, which displays echoes in many layers, which gives a 3D effect.
Bottom material
The bottom material can be determined from the
bottom picture colors and the tail length. For the hard
rock bottom, the echoes are largely shown in
reddish-brown or red with a long tail on the screen.
For the mud, gravel or algae bottom, the echo
screen has less red with a short tail.
Fish quantity estimation
The size and display colors of a school of fish are
indicators of the approximate quantity of fish.
Soft bottom
Hard bottom
Rough bottom
3-36
3-33
3
.
FISH FINDER
Mud & sand
Rock
Small echo
Large echo
Size of fish school echo
