How to Read a Fish Finder Correctly

By Richard | Fishing Advice

how to read a fish finder
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If you’re new to fishing, particularly kayak fishing, you'll want to purchase a fish finder and know how to read a fish finder correctly.

As its name suggests, a fish finder is a device that helps you find the location of the fish you want to catch.

It also helps you discover where large numbers of fish congregate.

The higher the number of fish gathered in an area, the higher the chances you have of catching them.

With the fish finder, you can significantly increase your chances of achieving this goal, plus you will get a pretty good idea of the conditions at the bottom of the water.

It doesn’t matter how amazing your fish finder is; you’ll just be wasting money if you don’t know how to read it.

Today, we’ll provide information that a fisher needs to know about reading a fish finder.

How to Read a Fish Finder

Each fish finder comes with a set of features unique to the device.

Some have screens displaying the signal from the transducer, while others can be linked to your iOS and Android devices via Wi-Fi or Bluetooth technology.

Either way, the first step to reading a fish finder is to understand how your particular instrument works.

Then you must know what the items displayed on the screen means.

How Do Fish Finders Work?

A fish finder is an electronic instrument that relies on sonar technology to determine the location of objects underneath the boat.

Some high-end models come with GPS, giving them a significant accuracy boost.

That said, a major component of every fish finder is the transducer, the part of the device that comes in direct contact with the water.

The Transducer

In most cases, the transducer is at the lowest portion of the boat. You can consider it the “eye” of the instrument that is mostly responsible for locating schools of fish.

The transducer functions by sending electronic pulses into the water. If any of these pulses encounter an object, they immediately send a signal to the receiver.

The length of time it takes for the signal to be received determines the kind of object encountered.

The machine’s software then analyzes the signals and creates an image from it.

The picture you see on the screen is not exactly the clearest. You will need to know how to interpret the lines, arches, and colorful blobs on display to have a good idea of where the fish is exactly.

What Does Fish Look Like on a Fish Finder?

Reading the fish finder, like casting a fishing rod, is an art. It involves following a few simple steps that will help get you on the right track.

Step #1: Identifying the Fish

The purpose of a fish finder is to increase your chances of making a catch.

It can be difficult when you don’t know the first thing about identifying the fish that appears on your screen.

Of course, the screen won’t just display the fish, but it will also show everything else underneath the boat.

Here are the common items displayed on the screen and their meaning:

Fish Icons

Fish displayed on the screen can come in the form of fish icons, but you have to be careful with these icons since they can also represent plants, rocks, and other objects beneath the water.

Each fish finder has an ID that helps you unlock fish icons. These icons come in varying sizes and shapes, which, generally, make it easier for you to tell apart fish from plant or rock.

That said, there are plenty of instances where you can't immediately identify what the object is and, therefore, have to be patient.

Time and constant practice are what ultimately make you a pro at identifying icons.

Fish Arches

Signals coming from the transducer usually appear as lines and arches. Understanding this process is key to saving yourself a lot of time.

Compared to fish IDs, arches shown on the screen are a lot clearer.

For instance, if you see a large arch depicted on screen, it means a large fish is right below you.

Similarly, if the arch is small, the fish underneath or surrounding the boat is also small.

how to read a fish finder

Step #2: Determining the Fish Size

It’s not all the time that the size of the arch or ID accurately represents the size of the object below.

Sometimes, further analysis has to take place before you can come up with a clearer picture.

For arches, you need to evaluate their length, thickness, and width further. 

Fish Arch Length

More often than not, you’ll be disappointed if you think that a long fish arch automatically translates to a large fish.

Thus, you’d be better off measuring the arch’s length as time, which means what’s displayed on the screen is directly related to how you are positioned with the fish.

For instance, the screen will depict a continuous line if the fish in question is motionless, but this doesn’t necessarily give you an idea of how large or small the fish is.

In the case where the transducer detects two fish moving at various speeds, the slower-moving fish will show a long line while the faster-moving one will present a short line.

Again, whether the fish is small or large won’t necessarily apply in this scenario.

Fish Arch Width

Since you can’t rely on the length to judge the fish size, perhaps you’ll have better luck with the width.

In this case, you must always consider the vertical width when reading a fish finder.

Regardless of how long the arch is, if it’s width is considerable, then it’s a big fish. Generally, if the arch is thicker, then the fish is larger.

Arch Fullness

There’s a full arch, and there’s also a half arch. These two are differentiated based on the position the fish is swimming in the sonar.

For fish located in the cone of the sonar, you’ll see a full arch depicting them. On the other hand, for fish swimming in a section of the cone, you’ll see a half arch.

Full arch doesn’t necessarily translate to big fish in the same way that half arch doesn’t necessarily represent small fish.

Again, fish size is dependent upon the thickness or width of the arch.

Step #3: Finding Bait Fish

Baitfish are usually represented as dots, dashes, or lines on the screen. Such fish types are often found in groups underwater.

You can also use the arch’s thickness to identify trophy fishes.

Step #4: Identifying the Various Structures Underwater

When you’ve mastered the use of fish finders, you’ll be able to do a lot of stuff, including identifying the bottom’s depth and other structures within the water.

For this part, you will need to access the depth feature of the transducer. With this function, you can accurately determine the depth of the water.

It also clues you in on the kinds of fish that would be swimming in those depths.

You can find the depth feature on the top corner of the display screen.

It tells you how deep the water is in meters and helps you discover how the bottom is structured. In this way, you can determine the location of drop-offs.

Once you have noted where the drop-offs are, try scanning the area using a thinner beam to reinforce the truth behind the image you’ve obtained.

It also helps you steer clear of dead zones. If you happen to be scanning a wide area, set a depth alarm that alerts you once you've reached the chosen depth.

The color on your display can also help you identify structures like logs and brushes.

You also have weeds and vegetation, depressions, points, and underground objects that represent different colors due to the different sonar frequencies they give off.

What Do the Colors on a Fish Finder Mean?

One thing you need to keep in mind about fish finders is that they can either come in black and white or colored.

A colored fish finder model will depict darker colors if the signals received by the transducer are stronger.

The more powerful the echoes returned by the transducer, the darker or stronger the colors on display will be.

Typically, the darkest colors on your fish finder will be echoes coming from expansive structures like the seabed.

Final Thoughts

Can you be an angler without a fish finder? Of course, you can, but that doesn’t mean you can reach your true potential.

Most of the time, you’ll be playing second fiddle to the more experienced fishers using high-tech gadgets like the fish finder.

With their knowledge and understanding of fish finders, they will always know the best places to spot and catch fish.

To become the best angler you can be, you must know how to read a fish finder.

Not only does a fish finder help you learn the fish's location, but it also helps you discover how the underwater world is structured.

That way, you can pick the best fishing spots and avoid dangerous locations at the same time.

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