Fish finder settings for tuna, menu by menu: Garmin, Lowrance and Simrad
Sounders leave the factory set for the average angler: everything on auto and a clean picture. For tuna, which return little echo and move fast, that is a problem. These are the settings that matter, with their name on each brand and a starting value. Golden rule: change one parameter at a time and, once it works, leave it.
| Setting | Garmin | Lowrance / Simrad | Starting value for tuna |
|---|---|---|---|
| Gain | Gain: Auto High / Auto Low / Manual | Sensitivity / Gain (Auto + offset) | Manual or auto +2 to +10. Raise until you see a little grain; over 100–150 m accept noise in the layers you do not fish. |
| Range | Range: Auto / Manual | Range | Manual, fixed to your working depth (0–80 m trolling) so the screen does not rescale. |
| Frequency | Frequency: 50/200, CHIRP Low/Med/High presets | Frequency: 83/200, Medium/High CHIRP | Split screen: medium band (or 50 kHz) on one side, high on the other. |
| Fish symbols | Fish Symbols (4 modes) | Fish ID | Off. They hide the real shape of the mark. |
| Real-time echo | A-Scope | Echo expanded / A-Scope | On: tells you whether the fish is under the boat right now. |
| Noise reject | Noise Reject / Interference | Noise rejection (low / medium / high) | Off unless other boats interfere; it also erases shallow fish. |
| Surface noise | Surface Noise | Surface clarity | Off or low: removes what happens in the first metres. |
| TVG | TVG (Time Varying Gain) | — | Low. Compensates the weak signal at depth; high cleans too much. |
| Screen speed | Scroll Speed / Pic. Advance (1/1 to 8/1) | Scroll speed | Normal trolling; fast vertical. |
| Ping speed | — | Ping speed | Medium; raise it with interference or vertical. |
| Colour | Color Gain / Color Scheme | Colorline / Palette (1–14) | Bottom-fill palette (13 on Lowrance) for fish tight to the bottom; no fill to judge hardness. Contrast 70–78%. |
| Bottom zoom | Bottom Lock / Zoom | Bottom zoom (split) | Jigging: split screen with the last 20 m above the bottom magnified. |
| Bottom line | Edge / Depth Line | — | Edge on: highlights the strongest bottom echo and helps read hardness. |
Set-up sequence
- Restore factory defaults once, to start from a known point.
- Check that the display recognises the exact transducer model; with the generic one, readings are worse.
- Fix the range to your working depth and the frequency in split screen.
- Raise gain until you see grain; back off one step. Turn off fish symbols, noise reject and surface clarity.
- Choose the palette and do not change it: the eye learns colours.
- Turn on the A-Scope and, if you fish vertically, bottom zoom.
- Save a screenshot of every fish landed with its species and depth.
What no menu fixes
Losing bottom when accelerating, diagonal noise lines or a jumping depth are almost always installation: transducer in bubbles, cable next to the engine's, poor earth or a through-hull at the wrong deadrise. Before touching ten settings, look at the transducer. How to choose and mount it: transducers for tuna.
Sources
- Garmin, echoMAP CHIRP manual: Advanced Sonar Settings and Sonar Noise Rejection Settings (Gain, Noise Reject, Surface Noise, TVG, Scroll Speed).
- Garmin, Sonar Frequencies.
- ONNautic, sensitivity on Lowrance and Simrad, scroll and ping speed and palettes and fish position (Spanish).
- In-Depth Outdoors, reading Lowrance (start from factory, leave some clutter on screen).
