How to Read a Fish Finder

If you rent a fishing boat, there’s a good chance it will have a fish finder, and learning how to use it will almost certainly boost your success rate. Fish finders let you peer down through the depths and see if that hotspot is loaded up with fins and tails or if it’s barren. But before we get to reading the fish finder’s LCD screen, here’s a simple explanation of how a fish finder works.

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How fish finders work
How to use a fish finder
How to read a fish finder screen

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How Fish Finders Work

Think of your fish finder and its “transducer,” the part of the system located on the bottom of the boat, as a loudspeaker and a microphone. The loudspeaker shouts out with sound waves that make “pings” that travel down into the depths. When the sound waves strike something like a fish, the bottom, or a wreck lying on the seabed, they bounce back, and the microphone hears it.

The data then travels through the wires connecting the transducer to the fish finder at the

How to Use a Fish Finder

Each fish finder operates a bit differently and carries slightly different displays and adjustment features, but most modern units are easy to use and very intuitive because they’re patterned after cell phone interfaces. Whatever the fish finder you may find at the helm, we have some great news for you: most modern units have automated settings, and the vast majority of the time, simply leaving them on the auto settings will provide optimal results.

However, there are still a few settings you should be aware of. Anglers focused on the bottom only may want to zoom in on the lowest levels of the water column and the bottom itself either by adjusting the range or utilizing a “bottom lock” feature (auto-ranges close to the bottom). Zooming in generally provides enhanced detail and makes seeing small fish or separate targets easier. Conversely, if you’re only focused on the upper ranges of the water column, you may want to zoom in on the surface waters.

Sensitivity is another setting you need to know about. Generally speaking, auto-mode will set sensitivity right where it needs to be, but sometimes water conditions or anomalies can fool this feature and leave a screen cluttered up with false positive returns. You may want to turn the sensitivity down a bit in that case. And if the unit isn’t detecting any returns, you may need to boost the sensitivity.

Some units also offer various color palettes and contrast levels. Using these is mostly a matter of personal preference, so feel free to change these and experiment a bit as you figure out what presentation makes it easiest for you to interpret the returns on the screen.

Finally, you may need to change the unit’s frequency at some point. Anglers who remain in relatively shallow water are usually best served by leaving the fish finder on its high-frequency setting, usually 200 to 240 kHz. But when venturing out into the ocean and you’ll be in depths over 500 feet it may be necessary to change to low frequency, usually in the neighborhood of 50 kHz.

Note that many modern “CHIRP” fish finders utilize a band of frequencies simultaneously and may not need as much or any adjustment depending on the specific unit, depth, and conditions.