Bump
or Fish
If you can’t find fish
you can’t catch them. I will show you one way to find hidden fish.
Fish close to the bottom
are sometimes displayed as bumps. You have 2 ways to decide if a bump
on the bottom is a fish. You can drop an underwater camera or use high
definition color sonar. Fish return weaker echoes so they display a
different color than the bottom depending on the setting of your colorline
and sensitivity.
Example 1 shows a fish near
the bottom showing as a bump. The fish is displayed as a bump instead
of an arch because the tips of the arch are hidden in the bottom display.
You will notice the fish on the left has arches because it is closer
to the transducer. The “bump’ fish has a different color
than the bottom because it is returning a weaker echo.

Example 2 has the sensitivity
and colorline poorly adjusted and the difference is not displayed.

Example 3 displays boulders
as bumps. These bumps have similar echo strength as the bottom therefore
they return more signal than the fish. One fish is displayed as a weaker
echo return. With Lowrance color units on the default screen, white
is no echo return, blue is weaker than red and yellow is the strongest
echo return. Other manufacturers use different colors for signal strength.

The best way to understand
setting of colorline and sensitivity is to log some charts with your
Lowrance and replay them in the SonarViewer as I have demonstrated and
adjust the settings at home when you are not distracted with fishing.
The log chart function and the SonarViewer are explained in my Lowrance
Tips section.
Definitions
Echoes: same as sound waves
or signals
Colorline: same as grayline but color instead of black and white
Transducer: sends and receives echoes