Finding Fish Near the Bottom with Sonar On June 01, 2013

If you can’t find fish near the bottom with sonar - 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.  Understanding your own fish finders colors will help you in finding fish near the bottom with sonar.


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.

Echoes: same as sound waves or signals
Colorline: same as grayline but color instead of black and white
Transducer: sends and receives echoes

by Bruce Samson under lowrance lowrance sonar

Comments are closed for this article.