How Does a Fish Finder Work?

What is a Fishfinder and How Does it Work?

In this article we have given a brief overview on How Does a Fish Finder Work.

What is a fish finder?

A fish finder, a sonar device that helps locate fish, is called a fishfinder. Sonar is short for Sound Navigation and Rangeing. A fish finder can come with GPS, marine radar, and a compass depending on which model you choose. This will help you navigate when you are on a kayak or boat. Fish finders use sound underwater to locate objects. They send out sound pulses to locate objects underwater and wait for the echo. There are many frequencies that can be used, from ultrasonic to infrasonic.

Does a fish finder help?

Your eyes may not be able to see the fish if you are out in open water. A fish finder is a great tool if you are looking for big fish. It can show you the dimensions of the fish that you are observing. Fish finders can be used in both shallow and deep waters. You can find fish as low as 10 feet in shallow water using side angle fish finders or wider angle transducer cones. This will help you determine the depth of your bottom. Many fish finders include a depth sensor that allows you to see how deep the water is. It is important to know the depth of the water to be able to identify the species of fish and what you can expect below. The depth of the water is displayed on the screen at the top left. In case you have a good area of fish, the GPS option can be used to find and return to the exact spot you were before.

How to choose the right fish finder?

There are three types: side scan, down scan, and hybrids. Side-scan gives an image of the sides and bottom of the boat while down-scan fishfinders scan below the boat. It can be difficult to choose. It is important to know what kind of fishing you are doing. A side scan is often more useful when looking for fish in heavy weedlines or exploring sea wrecks. A large screen is a good choice when buying a fish finder. The screen sizes range from 3.5″ to 16″. A 9” screen is a good middle-range option. You should also check the pixels to ensure a high quality picture. A smaller screen is more important if you intend to use it for kayaking. You can choose a lightweight, waterproof model or add a waterproof case.

How do I read a fish finder?

It can be difficult to read fish finders at first. However, it is essential to know how to do it correctly before you go fishing. While some fish finders can be used in color, others only allow you to use grayscale. Fish finders that support colors use them to visually present information. A stronger echo will be returned by objects that are dense or hard. The display color will appear darker if the echo is strong. The seabed, which is the bottom of the body, is often displayed as the darkest object. Some tools can show you an icon for the fish. Fish-ID technology converts raw data into an easy-to-use interface. Fish-ID devices can even display different symbols for rocks, plants and schools of fish. They are less accurate than they should be and may show seaweeds as a fish school or rock as a plant.

Arch fish finders are much more accurate, but they will only give you raw data in the form of lines and arches. These data will be your responsibility to interpret. Many fishermen mistakenly believe that a long arch is a sign of a large fish. The length of the fish does not reflect its size. Instead, you need to look at the arch width to determine how large it is. It doesn’t matter how short the arch is, if it is thick, it is likely that it is a large fish. Arches can also be half-full. Half-arch doesn’t necessarily mean a small fish. Its width is the best indicator. There are many models available. Before you go fishing, make sure to carefully read the manual. You will need to have both experience and preparation in order to read and understand the data and find fish. The fish finders are an invaluable tool. The more you know how to use them, then the more successful your fishing trips will become.

Boatmen use a fishfinder to find fish in the water. The technology used by fishfinders is the SONAR (Sound Navigation and Ranging). Fishfinders are an important tool in modern fishing and for leisure fishermen.

The digital screen used to display the fish’s location on a fishfinder can be either an LCD or CRT type. The fishfinder technology was developed in the 1990s. It has continued to be improved over time. The technology of fishfinders has evolved to include electronic compasses, radar and GPS. This makes the device more reliable than ever.

Modern fish finders are small computers that have special software to help the user see what’s going on under and around their boat. Many people are not tech-savvy and don’t know the basics of fish finders.

The truth is that fish finder manufacturers need to do better at educating customers. There are many myths and false information on the internet. This tutorial will help you to understand the basics of a fishfinder and show you how to read it.

How fish finders work – The basics

Fish finders come as a combo that includes a GPS receiver, fish finder head unit, and transducer. There are also many accessories that can be connected to fish finders, like networking devices, Bluetooth, and advanced sonar accessories like 360 Imaging, and Panoptix. This guide will only cover the basics of a fishfinder that you might have in the box.

How does a fish Finder transducer work?

The head unit would be the brain of a fishfinder system. The transducer would then serve as the eyes or ears. The transducer does the actual work of detecting the bottom and surrounding the boat. It sends data to the headunit and then the software uses its magic to paint the information onto the screen.

There are many types of transducers, but all have the same function. These transducers contain piezoelectric elements, which are similar to ceramics. They vibrate at specific frequencies and emit pulses of sound into water columns. Each “ping” from the piezo is followed by a return signal. The return signal is converted into an electrical signal that the head unit can process. This is what Sonar (Sound Navigation and Ranging) is.

There are many sizes and shapes of transducer elements depending on the frequency they are used. Traditional 2D sonar uses rectangular elements. Imaging elements are typically rectangular in shape to produce the thin high frequency signals required for imaging. CHIRP elements are capable of operating in a wider frequency range, often called broadband sonar.

Chartplotters & GPS

Your fish finder can track your location and chart it on top of a map if it has GPS capability. Most top fish finders today use an internal GPS receiver, but an external receiver can be used to show boat position heading direction even at very slow speeds. Fishing is much easier with a good GPS and lakemap. It’s great for navigation, scouting out fishing areas, and making waypoints so you can return to the exact spot later.

Garmin and Humminbird fish finders are now equipped with special software that allows anglers to create maps of unmapped waters by connecting any transducer to the unit. The software will create the map by simply allowing you to move in a crisscrossing pattern over an area. It’s almost like magic to see the bottom contours appear as you move.


There are many sizes available for fish finders, from 3.5 to 16 inches. The best thing to do is get the largest screen possible, as long as you have the right sonar features. The bigger the screen, you will be able to view more information at once. It is difficult to see the chartplotter and sonar on a 5 inch screen, but they look great on a 9-inch or larger screen.

Another thing to take into account when comparing screen sizes is their pixel density. The resolution of units will be the same in all sizes, including the 5, 7 and 9-inch sizes. Displays with 800×480 pixels are currently available from the top manufacturers in the 5-7 and 9-inch screen sizes. The pixel density of each screen size increases, so the images appear slightly blurrier. Most people believe that the increase in size is more important than the decrease in the pixel density. This is why it’s important to compare the units in person before making a purchase decision.


Fishing professionals will usually have several fish finders on their boat. Usually, one or two are at the console (steering wheels) and another is at the bow for casting. They can network the fish finders to make it easier.

Depending on which fish finder brand you choose, units can either be connected directly to each other or via a hub. Humminbird uses an Ethernet-based system, Lowrance and Garmin use NMEA2000-based systems. Ethernet is easy to use, but NMEA 2000 requires more technical skills and can be used to extend the network to other parts of the boat such as the radar and engine.

How to understand your fish finder’s display

What is the best way to interpret the screen?

Understanding the basics of technology will make it easier to understand how images are created.

The screen’s vertical dimension corresponds to depth, while the horizontal dimension refers to time. The top right corner represents what is directly below your boat at the moment. This could be, for example, that something in central part of the screen was 20 feet under your boat two seconds ago and something in bottom left corner 40 feet under your boat four seconds ago depending on your scale.

Certain colours are associated with specific return strengths. Red is the colour of something difficult in the Humminbird model (see video below). Both the thick lines at the bottom represent the floors of their respective bodies of water. You might be wondering where the fish are. The Humminbird model pictured would have them as the small blobs between the floor and the surface. Remember that not all what you see is fish. Anything floating in water can bounce a signal back at the transducer. You’ll become more adept at identifying what is likely to be a school or fish over time.

What does a fish look like on a fish Finder?

Reading a fish finder screen is one of the basics that everyone should learn, but somehow gets lost in the technology. I am always amazed when someone has a fish finder that costs $1,000 but doesn’t know how it works. These lessons will help you quickly improve your fishing skills.

2D Sonar Interpretation

To read the water column, traditional sonar uses a cone-shaped beam. Frequency determines the angle of the cone. The cone of 200 kHz is wider than that of 83kHz and covers a greater area. 83kHz provides more detail.

The fish finder is always listening and pinging, then paints the results onto the screen. The latest returns are to the right and older moves to the left. Imagine you’re sitting still. The screen will display the same depth. However, the bottom of the screen will appear flat as you are sitting at the same place. The cone would look like an arch if a larger fish swam through it. Because the distance from the fish at the end of the cone to the fish in the middle is shorter than the distance from the outermost, the arch forms.

Imagine you’re driving along a reef, with brush on the sides, and rock on the top. The screen’s depth changes as you move up the slope. The screen can appear like a lot of fish or blobs. The brush will be connected to the bottom. This tells you that it isn’t fish.

What makes groups of fish and brush look so similar to blobs in 2D sonar? Trees, brush, and dense fish groups can all appear as one-dimensional blobs. This is because the transducer picks everything within the cone. The Down Imaging sonar beam is narrower and returns only the portion of the beam slice that’s within the cone. This creates lifelike images.

What does hard bottom look on 2D sonar images? Hard bottom may have a bright yellow color with a thicker blue band below depending on what color you choose. The yellow blue color will turn orange as you get past the hard bottom and onto a muddy bottom.

What does sonar show fish looking like? If they are baitfish, fish can appear in the form of arches, clouds, or round marks. Because large fish have more mass, they will appear with a solid center color.

Do I need to use Fish ID? Although it is controversial, fish ID can help you identify where fish are relative to your cone. Many anglers don’t like having their screen filled with fish symbols. They prefer to interpret the fish themselves.

Interpretation of Down Imaging Sonar

What does Down Scan/Down Imaging look like? What is down imaging? This question is most common about down imaging. It’s very different from the traditional sonar that most people are familiar with. The Down beam cuts a narrow slice from the water column, so fish look exactly the same as on 2D sonar. Crappie will appear as small ovals and circles. They are often stacked together in groups around weed beds or timber. The bottom will have more bass than the top, and some of the larger schools will be a bit higher. Largemouths tend to stack up more than spotted bass.

How does Down Scan/Down Imaging show hard bottom? It is easy to see the hard bottom in imaging views. It will appear brighter than a soft bottom depending on the color you choose and have a thicker color band underneath. You can clearly see where the bottom changes from soft muck or gravel to hard bottom (sand, gravel or rock) if you sit on some bars or humps.

Side Imaging Sonar Interpretation

What does Structure Scan/SideVu/Side Imaging look like? It can be harder to spot fish because the side imaging beams focus on the sides rather than overhead. Brighter returns will be seen on fish, while if they are not at the bottom you can see their sonar shadow. How suspended the fish is can be determined by the distance between shadow and fish. Fish that hug tightly to hard bottoms will blend in and make it difficult to spot. However, fish with soft bottoms will be more visible because they have brighter returns. Baitfish will look a lot like cotton balls.

Lewis Mark is a vastly experienced fly fisher. His encyclopedic knowledge of fly tying has led to start blog on fishing. He also review Fishing equipment based on his knowledge and experience.