Basic Guide on How to Read a Fish Finder for Beginner

Over time, fishfinder technology has improved, making it practical for analyzing underwater topography and locating prospective fish grounds like drop-offs or underwater objects like mounds, sunken trees, or even wrecks. It also allows for the exact identification of schools of fish or individual fish.

However, understanding how to read fish finder screens correctly is a common problem most beginners face. This article will help you how to read a fishfinder and understand the information so you can enhance your fishing success.

The fundamentals of a fish finder

Fishfinder means they rely on sonar technology to provide comprehensive information about what’s right underneath your boat or kayak. The basis of fish-finding technology is to send and receive sonar signals.

The fish finder’s transducer transmits sonar sounds (called a sonar cone) into the water. When the sonar sounds collide with an item, they are reflected upwards, and the fish finder’s receiver decodes the signals and presents them as shapes on the screen. You may learn more about how fish finders function in our article.

In most circumstances, you’ll only be able to see what’s directly beneath your boat because a fish finder’s sonar beam is relatively narrow. However, once you grasp how to use this information to its full potential, you’ll have a huge advantage in spotting fantastic fishing possibilities. It’s vital to remember that fish finder sonar can only work in water, not in the air. You will be able to know the depth of the water below your boat, the temperature, the structure below you, and where the fish are. Furthermore, you will be able to judge the size of the fish. So figuring out how to read your fish finder is very important.

How to read a fish finder screen

Fish commonly appear on 2D sonar finders as arches with their apex pointing upwards on the screen. The fish are in motion, traveling through the sonar cone, and casting back a slightly different signal depending on where in the cone the sonar signal hits them, causing the arching effect.

Fish frequently appear as dots rather than arches on down imaging fish finders. It only displays a small portion of what’s directly beneath your boat because the down imaging sonar has a significantly narrower sonar cone.

Once you’ve mastered detecting fish arches or dots on your fish finder, you’ll be able to accurately identify schools of fish or even a single fish. You’ll even be able to see if the fish is near the area and where the bait is in the water.

You should be able to guess the size of the fish you see on the fish finder screen with a little experience. The larger the arches on the fish detector, the larger the fish. Remember that installing the range of your fish detector will also affect the size of the dome. With further practice, you’ll discern between signals emitted by fish and those emitted by other underwater objects such as plants and rocks.

Icons of Fish

Today Fish-ID technology is available on fish finders. The fish finder will automatically transform the sonar wave into a fish ID symbol on display. It makes it easier for anglers to identify them as fish or not.

While this sounds perfect in theory, the problem is that the technology isn’t always 100% accurate. The fish finder may misidentify other species like fish and not fish while missing other fish signals.

With a little experience, you’ll be able to identify the difference between fish and other items on your fish finder screen better than the fish-ID technology. Therefore, many experienced fishermen do not choose the fish symbols but decide to look at the domes. With just a little practice in deciphering fish arches, you will be able to identify them from other objects with greater accuracy than with fish ID technology.

How to decipher side imaging and imaging signals

Down imaging works by sending an extremely narrow sonar cone vertically down into the water, allowing you to see what’s immediately under your boat in incredible detail.

In contrast, side imaging employs two sonar cones sent sideways to the left and right of your boat. As a result, it assists you in gaining a general understanding of the undersea topography on each side of your boat.

As a general rule, utilize side imaging to check for prospective underwater landscape characteristics before switching to down imaging to locate fish in a specific place.

How to use a fish finder to estimate the size of a fish

A larger arch or dot, in general, denotes a larger fish. On the other hand, the arches can provide more information based on their shape, thickness, and width. Most fish finders will display the width of each arch, which you can use to estimate the fish’s length.

The shape of an arch, in addition to its breadth, is crucial. A large fish will appear on the screen as a whole, thick arch with a well-defined curve, but lesser fish will appear as partial arches that are not as thick or curved.

When looking at a school of tiny fish, they will appear as dots or short lines rather than arches. The most excellent method to identify them as fish is that they form a ‘cloud’ hanging in the water. This distinguishes them from more giant fish-like bass, either solitary or forming small groups with plenty of water space between individuals.

You should be able to spot a school of baitfish suspended in the water and numerous larger predators beneath them, which could be an excellent spot to cast your lure. Check out our post on how to read CHIRP sonar if you want to learn how to read a fish finder using CHIRP sonar.

On the fish finder screen can see how to distinguish underwater terrain. In addition to identifying fish, you also need to learn how to use your fish finder’s depth finding feature. The depth in feet or meters between the bottom and the water is displayed in the upper left corner of most fish finders. The temperature of the water is usually displayed just below the depth.

A fish finder’s display also provides information on the bottom structure and consistency beneath your fishing kayak or boat. You can take advantage of this by gently traveling around an area to locate noticeable objects that attract a lot of fish, such as a drop-down or a hollow log.

It will produce a highly detailed depiction of a potential area, and the fish found there. On a fish finder screen, underwater weeds appear as thin vertical lines. You should also seek holes, or depressions, which might hide lurking fish, and logs and underwater mounds, which attract fish.

There are various forms of bottom consistency

With a bit of practice, the sonar signal may reveal a lot about the consistency of the bottom. Compared to a muddy bottom, which appears broader and more “fuzzy” on a 2D sonar fish finder screen, a hard bottom will appear as a stronger, thicker line.

Knowing how to read a flasher is essential for ice fishing.

If you enjoy ice fishing, you might consider investing in a flasher fishfinder built exclusively for this reason. Unlike normal fish finders, it shows a one-way reading from the water column below your ice pit (for more on this, see our review of row flashers’ ice fishing tips and how they work).

A standard depth finder may also be used for ice fishing though positioning the transducer can be a nuisance correctly. It can even be used to blast sonar directly through the ice without cutting a hole.

What is a Garmin fishfinder, and how can I interpret it?

Beginner and professional anglers utilize Garmin fish finders since they are among the most trustworthy and frequently used brands. The sonar cone is presented on the right-hand side of the screen in the Garmin echo series. This is the water column directly beneath your boat, and it will provide a live signal of what is currently detected there. The 2D sonar map to the left tells you what was in the sonar cone a short time ago.

The color display has a color code, with yellow representing the strongest signals and blue and red representing the weaker signals. On the screen, fish appear as arches.

What is a Lowrance fishfinder, and how can I interpret it?

Lowrance is another well-known fish finder company with many benefits to offer. The most appealing feature of the Lowrance HDI transducer is that it can perform both 2D sonar and down imaging simultaneously. You can then choose a split-screen mode, which displays the sonar image on the left side of the screen or the down imaging on the right.

Each imaging technique has its own set of benefits. Down imaging is better for receiving more precise information on specific objects and fish with a higher resolution. 2D sonar imaging is better for gaining an overall overview of an area.

The sonar display on the Lowrance is similarly color-coded, with yellow and red indicating the strongest signal. In other words, if the receiver sends a stronger signal, the display will display it in bright yellow and red, while lesser signals will appear in blue or grey.


This tutorial aims to provide beginners with a quick and easy guide to interpreting the image the fish finder produces. Based on that, they can start seeing domes and then catch more fish or help anglers decide to install a fish finder on their boats and kayaks. We may not have covered them all in detail in this article, but you can read more articles on our website, where we have a lot of information on how to get the most out of the fish finder.

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