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How to Read a Fish Finder Screen

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Fish finders are devices that are designed to help anglers identify what is in the water beneath their boat. These devices significantly increase your chances of a successful catch. However, for that, it’s important to know how to read a fish finder screen. Without knowing how to use a fish finder, your investment will be just a waste of money. That’s why in this article, we’ll try to help you get the hang of understanding your fish finder.

How Does It Work?

A fish finder is a device that is designed to provide you with a view of the underwater world. The device consists of two main parts, which are transducer and display.

how to read a fish finder screen

The transducer is the brain of the fish finder system and it’s the best that does all the work of detecting what is happening below and around your boat. It does that by emitting sonar waves. When these waves reach an object in the water, they bounce back and return to the transducer. These returns are then converted into visual data, which you can view on the display of the unit.

The sonar returns can appear on the screen in the form of lines, arches and blobs. And knowing how to read these details will help you find more fish.

The sonar returns are displayed on the screen from right to left, meaning that the newest information will be on the right side of the screen and the oldest will be on the left.

In addition to sonar data, you’ll also be able to view on the screen other information, such as water temperature and depth. This information can also be very useful for various fishing techniques. For example, knowing how warm or cold the water is can tell you about the types of fish that could be found in this environment, which could be helpful for targeting specific fish.

Most fish finders also come with speed sensors, so on the screen, you should also be able to see your boat’s speed. You can use this information to adjust your boat speed to whatever fishing technique you’re using.

How to Read a Fish Finder?

Identifying Fish

You can start by learning how to identify fish since your main goal in using this piece of fishing equipment is enhancing your success at the catch. And when it comes to fish data, fish finders usually offer you two options of how they are displayed. They can be displayed as either fish icons or fish arches.

  1. Fish icons. This option is great for beginners. Since all the fish are displayed with fish icons, it is easier to differentiate them from plants, rocks and other objects. These fish icons can also be displayed in different sizes and lengths, helping you target specific species. They also display the depth of the fish, so you can know how deep to drop your lure. The downside of fish icons is that they don’t always provide the same level of accuracy as fish arches do. For example, a fish icon displayed as one fish might turn out to be a school of fish or a group of plants. So getting the hang of using fish icons requires a bit of practice.
  2. Fish arches. When using this option, fish is displayed as lines and arches. A stationary object or fish will usually be displayed with a line and moving objects will be represented by an arch. They can be bigger or smaller, wider or narrow. These arches and lines can also be brighter or darker. The darker colors translate to stronger signals, which means that the echo bounced off a hard and possibly large object. All this information can help you detect smaller and bigger fish. Since fish arches show more detail than fish icons, below we’ll go more into detail on how to read them.

Analyzing Fish Arch Length

A longer fish arch doesn’t necessarily mean a bigger fish. Since the length of the arch also measures how long the fish has been under the transducer. Due to this, a longer arch will mean that the fish spent a longer time in the transducer’s beam. For example, if you see on the display a continuous line, it can mean that the transducer encountered a motionless fish.

Analyzing the Thickness of the Arch

The thickness of the arch is a better indicator of how big the fish is. A thicker arch with a solid red or yellow color in the center would usually indicate a larger fish since it would return a stronger signal. So, if you want to target bigger fish, always look at the thickness of the arch.

Half Formed Arches

A full arch means that the fish has crossed the entire sonar cone, from one side to the other. A half arch, on the other hand, means that the fish has swum only through part of the cone.

Identifying Bait Fish

Bait fish is usually displayed as small dots that are grouped tightly together. They can also appear as blobs. It will depend on the sensitivity setting you’re using.

Identifying Bottom

By reading the fish finder screen, you can also understand the type of bottom that the lakebed, seabed or ocean floor have. A thinner and brighter line usually means a softer bottom and a thicker, bold line would mean that the bottom is hard and less porous.

When analyzing the bottom, you can also find vegetation, plants and drop-offs. Vegetation will usually display a spotter return that will be in a vertical line. Drop-offs and depressions will be displayed as v-shaped dips in the bottom contour.

How to Read Down Imaging Sonar?

Down imaging sonar uses an ultra-high frequency beam, which produces images of what’s below your boat with a higher resolution than with 2D sonar. By getting more detailed sonar details, it makes it easier to differentiate between fish and brush piles, fallen logs and other submerged objects.

Reading down imaging sonar returns is similar to traditional 2D sonar. The information is displayed from right to left, with the newest being on the right. Other information, such as fish arches, will be displayed similar to 2D sonar as well, but they will have more detail.

How to Read Side Imaging Sonar?

Side imaging also uses an ultra-high frequency beam. However, instead of sending it down, the transducer sends two beams to either side of the boat. This provides you with a wide view of what’s happening in the water around your boat.

This type of sonar displays sonar returns in a slightly different way. This sonar scrolls from top to bottom, with the newest scan information displayed on the top. The screen will also be split in the middle, with the line that goes through the middle representing the surface of the water.

Spotting fish on side imaging sonar is a bit harder since the beams are looking to the sides and not directly down. However, you can spot sonar shadows of fish when they are off the bottom of the water. And by analyzing the distance between the shadow and the fish, you can tell how suspended the fish is.

Fish that are hugging tight to a hard bottom will be more difficult to spot since they will blend in. However, you can easily spot fish on a soft bottom as they will stand out with brighter returns.

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