What is on the screen
Most fish finder screens look busy at first, but they all carry the same handful of things. The big numbers are readouts: how deep the water is right now, how fast the boat is moving and the water temperature. A ruler runs along one edge so you can judge depth at a glance. The colored picture fills the rest.
The most important line on the screen is the bottom. It is the strongest, thickest band, because the bottom reflects far more sound than anything floating above it. Everything between the top of the screen and that band is open water. Anything standing up from the band is something that rises off the bottom.
Tap a number below to see where that part is on a real unit. The photo is a Lowrance Eagle 7 in demo mode. Your unit may arrange things differently, but the pieces are the same.
The screen photos on this page are demo mode (the unit running its built-in simulator), not a real lake, so the fish, bottom and temperature are made up by the unit. They are here to show where things are on the screen. The drawings are TexCast diagrams of how sonar works.
An interactive drawing goes here in the app.
On the water
- Find the depth readout first, then find the same depth on the ruler. Once those two agree in your head, the rest of the picture makes sense.
- Look at the bottom band for changes: it gets deeper or shallower, thicker or thinner, brighter or dimmer. Those changes are what you are actually fishing.
- Look for anything above the band that is not the bottom: bumps rising off it, marks floating in open water, or clouds of small dots.
Easy mistakes
- Reading the water temperature as the temperature where the fish are. On many boats it is measured at the transducer near the surface, so it is the top layer, not the water at depth.
- Judging depth by how high a mark looks on a screen that has been zoomed. Always read the ruler.
- Treating the colors under the bottom band as water. Echoes keep coming back after the bottom; that area is not open water and not fish.
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