Finding locating fish is one of my secrets to catching fish. Fish will concentrate in certain areas and are not found everywhere. You can hunt for them at 2-mph or you can do it Doc’s way and search for them at 20-mph. I will show you how to do it and how to make it useful. This method of locating fish pertains to all species. Basically, fish are shown as horizontal lines when the boat is stationary, arches when the boat moves slowly and as vertical lines when the boat moves fast. You can also change the way a fish appears with the chart speed, but a fish arch will also change at different speeds, no matter what you set your chart speed  at.

The following examples are recorded using the log chart data feature on my Lowrance LCX 38 sonar / GPS unit.

Example 1 is 2 mph and 5 mph.

Example 2 shows fish at 20 mph and 4 mph.

Example 3 is example 2 adjusted for easier viewing.

By following these steps you can make the screen easier to read.  This is vital because you need to navigate safely at 20-mph and not be squinting at the screen. Set the unit to have a blue background, sensitivity and colorline should be increased a little, and the ping speed increased to 100%.
Sensitivity, colorline, and ping speed are all found in the sonar menu. Blue background is found in sonar features under sonar chart mode.
There are no exact numbers for the sensitivity and colorline because each model of Lowrance is different. You must adjust them to get the display picture you prefer.
When I am hunting for fish, I use the sonar cursor/depth cursor feature to place waypoints on the fish behind the boat so, I can find them when I turn around and troll over the waypoints.  This tool is very important when hunting for fish.
I recommend practicing in places that have lots of fish or baitfish.  Begin by logging a chart at 2-mph, 6-mph, and 20-mph and take them home and view them on the Sonar Viewer. Then practice adjusting sensitivity, colorline and blue background properly.  It Is much easier to learn this method off the water than trying to do it on the water in your boat driving down the lake. Till next time remember, be safe!

More information on the principals of fish arches can be found on Doc’s DVD Understanding Son and Interpreting the Display at www.hightechfishing.com
Additional information on logging charts, and using the SonarViewer are discussed along with a video on using the Sonar Cursor can be found at www.doctorsonar.com