How to Read a Fish Finder to Reel in Your Biggest Catch Yet

Years ago, I sailed out to sea in a chartered boat for a day of fishing. And if I knew how to read a fish finder, I might have caught the big one. You see, I expected the fish to look like, you know — fish. But that wasn’t the case at all.

Luckily, I wasn’t the captain of the vessel because that guy did know how to read a fish finder and was calling out to all of us where the fish were. He told us when, where, and how deep to drop our lines, all because he could read the amazing contraption.

Well, I did end up catching a flounder, who was a hell of a fighter and felt like the big one to me. And I’ll bet, once you know how to read a fish finder the right way, you’ll be able to pick the perfect fishing spot.




image by pexels

The first time you see a fish finder screen, you might be taken aback. Unless you know what you’re looking for, a fish finder screen can look like nothing more than random shades and colors.

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And reading a fish finder may not be something you get right away. Deciphering the structures under the water from the fish will take some practice.

But there are some key elements to look for, and once you’re familiar with those, learning how to read a fish finder just might be a piece of cake. Also, knowing how a fish finder works might help you understand what you’re looking at.


A fish finder works by sending a sound navigation and ranging (SONAR) wave down into the water. When that sound wave hits an object, it bounces back to the device, and a picture appears on the screen.

As long as the fish finder is on, it’s sending continuous sound waves into the water in a cone shape, and they’re bouncing back. This movement gives you a picture of what lies underneath the surface.

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The fish finder is also calculating the time it takes to get back up to the device. By doing so, it shows you how deep an object is, its size, and its density.


Now that we’re clear on how the device works, what you really need to know is how to read a fish finder. After all, that’s how you’re going to know where to drop your line.

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You’re generally going to have two kinds of fish finders: color or black and white. The good news is, whether you’re looking at color or shade, it doesn’t make a difference in how to read a fish finder. That said, things will be more clear if you have a color screen.

Why? Because the shading on a black and white screen may be harder to interpret. But, you’ll still be able to pick out what you’re looking for — fish.

When you’re reading the screen, though, keep in mind that all the information to the left is old data. So even though you might see that school of fish on your screen on the left, that doesn’t mean they’re still there.

The fish finder is only sending current data on the right side of the screen because it can only “see” what is currently in the sound wave cone.

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When you look at your fish finder screen, the first thing you might notice is the dark strip of black, red, or orange along the bottom. That, as you may have guessed, is the bottom of the body of water you’re in.

The sound wave is showing you a picture of either sand, rock, mud, or sediment at the bottom. The dark color tells you it’s a solid surface. The darker it is, the denser or harder the object.

Orange or yellow means the bottom is soft like sand or silt. And here’s a little tip: bass prefer a soft bottom. So, if you’re looking for bass, that’s where you’ll likely find them.

Also, along the bottom, you might see objects protruding up. These may be colored green, depending on your fish finder. No matter what color they show up, these are likely trees and grasses.

How do you know they’re not fish? Because of their color, shape, and the fact that they’re attached to the bottom. They’ll also be a stationary object, whereas fish typically aren’t.


How to read a fish finder to find fish is actually pretty easy. You’re looking for arches in the water. The arches are the fish entering and leaving the SONAR cone. These arches could be of varying colors based on the size.

Usually, if you see an arch with red inside, it’s a bigger fish.

You’re also looking for larger masses of arches in the water. Those are schools of fish. And the small bumps are baitfish. Also, look along the bottom. You’re looking for lines or arches not attached to the floor. Those are probably bottom-dwelling fish.

One other tip: You may see lines instead of arches. What does that mean? That means the fish is swimming along with your boat and is staying in the SONAR cone. So, instead of appearing as an arch as it enters and leaves the cone, the fish appears as a line.


Now that you have the basics, once you familiarize yourself with your own fish finder, you’ll be able to tell where to fish and where to drop your line. Play with the sensitivity of your machine, so the images below are more clear and make the most sense to you.

man chopping fish

image by pexels

If you see something that looks like a fish, but you’re not sure what kind — cast! See what you pull out of the water and make note of what that fish looks like on the screen. How to read a fish finder is all about knowing the basics and adding your experience on top.

Use your new found knowledge to find the perfect fishing hole and pull in your best haul yet.

Do you have any other tips on how to read a fish finder? Drop your line in the comments!

Featured image by: Amazon

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