Understanding Humminbird/Lowrance Sonar Auto-Sensitivity On August 12, 2016
Understanding bottom hardness is vital to understanding and catching walleyes.
Sometimes it is easy like this image with the hard bottom on the left.
I use Auto-sensitivity on my Humminbird and Lowrance models almost always. It works so well we never notice when it adjusts. Auto-Sensitivity mainly adjusts for depth. We need a higher sensitivity in deeper water since the sound that returns as you go deeper becomes weaker. A manual setting of sensitivity for 10 feet to get the optimal image would not show fish at 100 feet and this is where Auto-Sensitivity shines.
I’ll use examples from this summer when there were a lot of microorganisms in the water so you see a funny screen to help understand what is happening when the auto-sensitivity is working.
The first image shows rapid depth changes at a speed of 30 mph. Notice the clutter clears when I go shallow (green arrows).
The next image shows the suspended clutter change as I go up the slope. At the same time as the clutter changes, the bottom changes (green arrow). The Auto-Sensitivity has decreased the sensitivity at a certain depth. It is important to understand this when you are trying to determine bottom hardness as walleyes are often found by finding hard bottom.
The 3rd image shows what appears to be harder bottom on the right side of the image but this is caused mainly by the Auto-Sensitivity increasing the sensitivity as I go deeper (green arrow).
Harder bottom has a wider bottom band and stronger colors like the yellow. It is easily to fooled by this image and think there is a transition from soft to hard bottom which walleyes often prefer.
Auto-Sensitivity is a great feature but understanding its limitations is important for hunting hard bottom which can result in you greasing the pan for walleye more often.