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How to Read a Fish Finder Screen

According to recent statistics, in 2017, more than 49 million people in the United States participated in saltwater, freshwater, and fly fishing. This goes to show how prevalent fishing has become over the years. Anyone who has gone out fishing, whether for recreational or business purposes, knows how daunting catching fish can be.

This is where a fish finder comes in. With the help of this small but compelling device, you can see what is inside the water and locate the fish more quickly. Not every angler who purchases a fish finder is technology savvy, so reading it can be challenging. Not to worry, because we put together a comprehensive guide on how to read a fish finder.

How do fish finders work?

Almost every fish finder in the market uses CHIRP sonar technology. Unlike the standard sonar that sends out one frequency at a time, the CHIRP sonar, with the help of a transducer sends out multiple ranges of frequencies at a go. The fish finder then individually interprets each of these frequencies and gives you an extensive range of information and clear and well-defined images of whatever is inside the water.

Identifying Fish – How to Read a Fish Finder

How to Read A Fish Finder

The first step to learning how to read a fish finder is learning how to identify fish on the fish finder display screen. There are two ways in which fish finders display the collected data from inside the water, depending on its features. The fish finder can either show the actual, raw data or convert the raw data into a simple and user-friendly interface.

Most fish finders are equipped with a fish ID technology that is responsible for converting the raw data into much simpler information. If your fish finder has this feature, then identifying fish will be a piece of cake. Let’s take a look at how you can identify the fish on your device, shall we?

a) Fish Icon

With the fish ID technology’s help, the fish finder displays fish icons, which represent the fish and other objects inside the water. The fish icons come in different sizes depending on the sizes of the detected fish. Some fish finders have advanced fish ID systems that have different icons representing rocks, plants, and various schools of fish.

This feature, however, does have a downside. Some fish finders have fish ID systems that are not entirely accurate. They will display what is actually a rock as a plant icon or a group of plants as a school of fish. This is why you have to be extra careful when purchasing a fish finder, as you would want to look for one with an accurate fish ID system and of course, take time to understand how the fish ID technology works.

b) Fish Arches

While most fish finders use fish ID technology to represent fish and other objects inside the water in the form of fish icons, other fish finders display the information collected by the transducer in the form of arches and lines. Most users find this feature much easier when it comes to identifying fish, compared to the fish ID system. This is because the arches and lines are more precise and well-defined, such that when your device shows small arches, it means that the transducer has detected small fish and if it shows bigger arches, then it has detected bigger fish.

This feature, of course, has it’s downside. The arches do not clearly represent other objects inside the water like rocks and plants.

Judging Fish Size

We have looked at how you can identify fish on your fishfinder using the fish icon or the fish arches. We have talked about how small arches represent small fish, and larger arches represent large fish, but that is not always the case. To accurately identify the size of the fish detected by your device, you need to pay close attention to the arches’ length, width, and thickness.

a) Fish Arch Length

Many fish finder users make a mistake of associating the length of arches with the size of the detected fish, but that is not the case. The length of the fish arches mainly represents the movement of the fish. If your transducer has detected two fishes that are moving at different speeds, the long arch represents the fish that is moving at a low speed, while the short arch represents the fish that is moving at high speed. It is crucial to note that these fishes might be big or small.

b) Fish Arch Width

We have just mentioned that the length of the arches on your device’s screen does not represent the detected fish’s size, but what about their width/thickness? Well, the width or thickness of an arch represents the size of the detected fish, regardless of the length. So, the thicker the arch, the bigger fish.

c) Half or Full Arches

When you receive a full arch on your fish finder’s screen, then that means that the detected fish has moved through the entire sonar cone. On the other hand, if you receive a half arch, then the fish has just gotten through a section of the sonar cone. Just like the arch length, half or full arches have nothing to do with the fish’s size.

Pro tip: To accurately identify the size of fish, always concentrate on the thickness/ width of the arches you are receiving on your fish finder’s screen.

d) Finding Baitfish on Your Fishfinder

Most fish finders will either show dots, dashes, or lines as baitfish, which in most cases, is similar to vegetation. To accurately identify if what your fish finder has detected is baitfish, here are some tips to keep in mind.

  1. Almost fish finders will display baitfish in a different color to vegetation.
  2. Unlike vegetation, baitfish are not at the bottom of the water. Baitfish are usually suspended in the water.
  3. In most cases, baitfish are shown on the screen as balls, which are displayed like a cloud or cluster, rather than dots, dashes, or lines.

e) Spotting A Trophy Fish on Your Fishfinder Display

The easiest way to spot a trophy fish on your device’s display screen is to pay attention to the pro tip we mentioned earlier. To accurately identify the detected fish’s size, always look at the width/thickness of the arches, not the length.

Read more: Best Garmin Fishfinder Reviews

Identifying Different Types of Underwater Structure

How to Read A Fish Finder

We have looked at how to identify fish inside the water accurately, but how about other underwater structures? Well, the features we have mentioned above cannot help you. This is where a depth finder comes in. Most fishfinders’ transducers have this feature. As the name suggests, a depth finder helps you know the depth of the water and help you identify fish within that depth range and other water structures.

It also helps you determine the water temperature, which is very important if you want to catch fish successfully. Usually, this feature is located on the top left corner of the screen. It works using meters as it’s unit of measurement. So, let’s look at how to identify other underwater structures, shall we?

a) Vegetation And Weeds

According to recent research, a massive population of fish inhabit in densely vegetated areas inside the water. This is because vegetation has a plethora of benefits to fish and other water creatures, including; food, shelter, and oxygen. This is definitely an excellent spot to catch fish, right? But how can you know where to find vegetation and weeds inside the water? With the depth finder’s help, your fish finder will show vertical lines or spotter returns, in case you stumble upon vegetation and weeds.

b) Depressions

If you are going carp fishing, then depressions should be your number one target. Usually, it is the fish themselves that make the depressions. So how do you spot them? You just have to look out for small, v-shaped dips in the bottom contour as you are reeling or trolling.

c) Points

Spotting points is much easier since they are slower than drop-offs. However, to get an accurate reading of how steep the incline is, you need to maintain your speed as troll or reel. Although most users prefer scanning with a narrow sonar beam first, you should begin scanning with a wide sonar beam, then switch to a narrow sonar beam, to be able to pick all the humps and shelves.

d) Other underground objects

When you go out fishing, you usually expect fish and vegetation inside the water, right?  What if there is something else like a car or the bones of an extinct animal species? But can your fishfinder really detect that? Well, the good news is it can. To accurately identify the object inside the water, it’s essential to pay close attention to the return signal’s shape and strength. If it happens to be a hard object, you will notice that the return signal repeats itself.

Here are a couple of tips to keep in mind when you are trying to identify underwater structures.

  1. Always troll or reel at a slow speed, to clearly see the bottom of the contour and quickly identify drop-offs.
  2. When you identify a drop-off, always scan again with a narrower sonar beam to obtain a more precise and broader picture of the bottom contour and help you avoid any dead zones.
  3. If your fish finder has one, always set a depth alarm if you are paddling in a large area. It will give you an alert once you get to your preferred depth.

Using your fish finder to judge bottom type and hardness

Regardless of the fish species, you are trying to catch, knowing the type and hardness of the bottom of the water body you are fishing in is also a crucial piece of knowledge that will help you when it comes to catching fish. Let’s take a look at the factors to consider when judging the bottom type and hardness.

a) Thickness

When your fish finder’s transducer returns a strong echo, it is displayed on the screen as a thicker and bolder line. That means that the bottom of the section of the water body you are in is hard. On the other hand, if the transducer returns a weak echo, and is displayed on the screen as a thin, light line, then it is very likely that the bottom is the transducer has encountered is soft. However, it is essential to keep in mind that your sonar’s sensitivity can affect the thickness of the displayed line. That is why you should always adjust the sensitivity of your sonar.

b) Color

Fishfinders either have colored or black and white display screens. Most fish finders out in the market have colored display screens. So, if the transducer returns a strong echo, it will be shown on the screen as a stronger and darker line. On the other hand, if it returns a weaker echo, it will still be displayed on the screen as a dark line, although it will be lighter.

c) 2nd Returns

We mentioned earlier that if your transducer detects a hard object inside the water, the return signals always repeat themselves or bounce. These returns are known as 2nd returns. They are usually displayed on the screen when the transducer detects hard objects or surfaces.

Down Imaging Sonar Interpretation

Down imaging works pretty much the same way as a traditional sonar. Basically, the transducer sends sonar beams down beneath your boat. With down imaging, you do not gather a lot of information and cover more water; therefore, you will receive low-quality images.

For example, vegetation and dense schools of fish appear like indistinguishable blobs. Crappie will look like small oval or circles stacked on top of each other. Spotted bass will look like they are stacked on top of each other.

Hard bottoms are very easy to see with down imaging. According to your device’s color palette, a hard bottom will be represented by a brighter color with a thicker band of color underneath. If you look closely, you will notice how the color changes when the bottom transitions from hard to soft.

Although it may not seem like it, down imaging is beneficial when you are fishing in deep waters, and it works perfectly even when you are traveling at high speed. However, it does not give you as much horizontal information as side imaging. For instance, you can identify a fish, but you cannot tell which side of your boat it is.

Side Imaging Sonar Interpretation

When it comes to side imaging, the transducer sends sonar beams to the sides of your boat. This means you can scan more water, gather a more extensive range of information, and receive high-quality images on your display screen. However, it can be a little hard to spot since the sonar beams are facing out to the side.

With side imaging, if the fish is not at the bottom, you will see their sonar shadows. The distance between the fish and its shadow will help you determine how deep the fish are suspended in the water.

Fish that are in close contact with a hard bottom will be difficult to spot since they easily blend in with the surface. On the other hand, fish on a soft bottom will stand out because of their brighter returns.

Read more: Garmin Striker 4 Review

Frequently Asked Questions

1. How do I read a Humminbird fishfinder?

Humminbird fish finders are arguably one of the easiest fish finders to read and operate. This device offers a simple and user-friendly interface, so even a person who uses a fish finder for the first time can easily operate it. The Humminbird fish finder allows you to read the display screen in two ways, either through the graphical display or numerical display.

The display screen clearly shows the water depth, temperature, fish images, and other relevant information. The fish finder has function buttons, like the on/off buttons, menu button, to mention a few that are very easy to operate. So, all you have to switch it on and follow the step to step guidelines on how to operate it.

2. How do I read a Lowrance fishfinder?

Reading a Lowrance fish finder is pretty much straightforward. Once you have switched it on, and you are sure that it is operating smoothly, you will see a display of numerical and standard value in the upper left corner. This represents the water depth. At the bottom of the screen is a line that stretches throughout the width of the screen.

The line indicates the bottom of the lake. The objects above the line show the objects inside the water. For best results, always adjust the unit’s sensitivity as high as possible. However, be careful not to cause clutter on the screen. Also, ensure to set the automatic mode active. This will give you a more clear value of the water temperature, depth, and boat speed.

3. How do I read a Garmin fishfinder?

Garmin is one of the top manufacturers of high-quality fish finders known to be simple, affordable, and easy to operate. Reading a Garmin fish finder is a breeze. You will, first of all, have to turn it on using the red button. Once it is up and running, you will notice some numbers displayed on the screen’s upper left corner. These numbers indicate the water depth measured in feet and temperature, which is shown in Fahrenheit, not Celcius.

At the bottom of the screen, you will see a line extended throughout the screen’s width. This line represents the water surface. When the line inclines upwards, it means that the water is shallow, and if it goes in a downward direction, then the water is deep. You will also see some lines or signs that stretch off of the surface of the lines. It’s important to note that they represent other objects inside the water but not fish. You will also notice some hook signs in the middle of the screen. These signs indicate the fish.

Wrapping up – How to Read a Fish Finder

A fish finder is one of the must-have fishing tools that will help you make the most out of your fishing experience. But if you do not know how to read, it will be as good as useless. With this all-inclusive guide on how to read a fish finder, reading yours will be a piece of cake. Just be sure to read the instructions to get yourself acquainted with the fish finder model you have purchased.

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  • July 18, 2022
Paul Dudley

Paul is the owner and founder of . His passion for ham radios and fishing lead him to create this site. He loves playing with his radios and doing many other outdoor activities