How to Use a Fish Finder?

Step by Step Guide to Use a Fish Finder

How to Use a Fish Finder- Step by Step Guides. Fish finders are a must-have for fishing. It is easier to locate and catch fish if you know where to look instead of moving your boat aimlessly around the water in search of a good spot.

Those small devices help you by locating the hot fishing spots and detecting any obstacles on your way. With their integrated GPS, they can also be used to save your favorite areas. You need to learn how to properly use fish finders to get the most out of them.

What is Fish Finder?

Fish finders can be described as SONAR (SOund Navigation RAnging) devices. They use sound waves from the device to locate objects below your boat.

The sound that is emitted from the device travels rapidly downwards (about one mile per second), and then travels to the bottom or objects between the bottom of the body. These reflections are sent back to your device. The device sends a second pulse when the sound wave is reflected back at it. This process continues indefinitely.

The device uses a computer and software to measure the time it takes for a sound wave’s return and the strength of that sound wave. This allows the device to determine depths of objects. These sound waves are converted into electrical signals and displayed in a format that is easily understood by boaters and fisherman.

This is a very brief and simple explanation, but feel free to check out this guide for a deeper understanding of how SONAR works.

Fish finders can be quite expensive. There are many options available in a variety of price points. Although we won’t be going into detail about how to choose the right fish finder, you might be interested in finding one that fits your budget. FishingPanel has a guide that will help you find a fish finder under $500.

How do fish finders work?

Fishfinders are small computers which use SONAR to locate objects under and around boats. Many boats are equipped with GPS.

The transducer is the portion of the fishfinder that sits in water. The transducer is located on the kayak’s flattest section.

The transducer functions in the same way as the eyes of a fishfinder. It contains elements that vibrate and send electronic pulses through water. These pulses bounce off objects and return to the receiver.

Software analyzes both the time it took for the signal to return and its strength. This data is transformed into an image on the screen.

However, the image may not always be clear. You may see blurred, colorful lines, blobs or arches. You won’t be able use the technology to locate fish if you don’t understand what you are looking at. This article will discuss how to read a fishfinder.

Understanding Sonar

Sonar transmits frequencies in a cone-shaped manner. A 200 kHz sonar beam will have a larger cone than one at 83 kHz. Although it will cover a greater area, it will provide less detail.

How to Install a Fishfinder?

Small units are often ideal for small boats. A fishfinder can be installed on any type of vessel, including a kayak, powerboat or motorboat.

Some kayaks for angling have fishfinders. Some kayaks have fishfinders, while others don’t. However, they might have a mounting point for a transducer that allows you to not have to drill into the hull blindly. This video shows how to mount a fishfinder on kayaks.

You can choose to have a floating or over the-the-side transducer if you are concerned about permanently installing a fishfinder. This fishfinder is ideal for use with an inflatable or fold-up kayak.

Casting transducers is possible. This is useful when you are navigating the waters in a kayak slowly. To investigate a specific spot, you can move the transducer a few feet away.

A fishfinder is usually attached below the hull to attach to a large boat. Most kayaks are thin enough to place the transducer inside the hull. This could eliminate drilling holes in the boat.

Fishfinding Features

Fishfinders are a great option if you want to find fish. Let’s discuss the readings that will impress your friends when returning to shore.

You can learn a lot from the thickness and color of lines and blobs. At the bottom of the screen will be the bed of the water body you are traveling in. A thicker line means that the surface is harder and less porous. You might be traveling on clay if you see a think line.

A hard bottom is usually represented by a yellow band and blue below it if you have a fishfinder that uses 2D sonar. Depending on the color scheme of your device, a mucky bottom might not have defined bands and look orange.

This information will be relevant to your fishing experience. You will be better able to see the action in each environment if you have a greater understanding of it.

You’ll notice surface clutter at the top of your screen. This is caused by water disturbance from your boat, paddle, or waves.

You will see the fish as blobs or arches between the water surface (and the ground) and clouds. It should be possible to distinguish between individual fish and schools. Because they emit strong sonar signals, larger fish may have a darker spot in the middle.

As you move, the display on your screen will change. You move slower and the picture will stay stable. On the right you will see the most recent information. The older information is shown in the lower part of the display.

To see what is directly below your boat, look to the right side. The data to your left shows you what you have already passed by.

Fish finders can transform raw data into icons to help you differentiate between fish and other objects beneath the water surface. Some simply show you lines and arches that you can decipher.

Fish ID Technology

Fish-ID technology uses an algorithm to analyze your data and provide a clear representation about where the fish may be. This interface is more intuitive than one that displays raw data.

This technology allows fishfinders to display icons that show the location of plants, rocks, and schools of fish. These objects will be displayed in the distances shown on the sides of your screen. This information will allow you to understand the depths of these objects and help you decide where to cast your line.

Fish-ID technology has a downside. It isn’t always 100% accurate. To distinguish between a school of fish and a group of plants, you must rely on a computer.

It is possible to become dependent upon the icons and not use your analytical skills to identify if the objects are fish or another species. Fish-ID technology has a high number of false positives.

While some people feel like fish-ID technology is a gimmick, this feature can come in handy in certain instances, such as detecting fish within brush or another type of cover. The color image will show submerged trees or weeds in a mass of jumbled colors. If there are fish in the brush, it should also show fish icons.

Arch Fish Finders

Learning how to use an archfish finder can be difficult. After you’ve mastered the skill, it will be easy to read the screen. It’s almost like learning to read in another language.

The data is shown by arch fish finders in the same way it was transmitted to the transducer. A straight line will be shown if an object is stationary. An arch will be created by a moving object. An arch will appear on the screen when a moving object is a fish.

The object’s size is determined by the size of its lines and arches. Bigger arches indicate larger fish. Sometimes you will see only half of the arches. This indicates that the fish did not pass through the cone of the transducer. Fish that are close to the ground may show fluctuating arches.

While it might seem easy to read a fishfinder on paper, deciphering its display in practice might prove more difficult. Learn the meaning of the marks on the screen by taking your time. The more you use the device, the better you will become at it.

Combination Fishfinders

You can switch between the two modes of some fishfinders and see either the raw data or the fish icons. Switching between the arch/line and fish-ID modes can be confusing. The fish-ID mode displays a lot of fish, while the arch/line mode has fewer arches.

This example shows the unpredictable nature of fish-ID technology. It might appear as separate icons for fish if you move over plant life.

You can determine if they are fish by looking at their placement. If the fish icons appear to be vertically stacked, they are most likely plants. The fish icons that appear to be connected to ground surface are likely to be plants.

Single Vs. Dual Frequency

A single frequency fishfinder emits one cone of sonar. A dual frequency fishfinder allows you to receive data from both cones simultaneously. The cone at the center provides more detail while the cone at the lower frequencies tells you what is around it.

You might see the information on a split screen. Fishfinder technology will show the blue fish in the high-frequency cone and orange fish in the low frequency cone. Although they may appear to be hanging out together, the orange fish are actually the ones surrounding the boat. The blue fish are those directly below you.

Side Imaging

Side imaging can make it difficult to interpret on a fishfinder. Your transducer must be properly installed and placed in the correct place. The transducer should be located below the hull with a clear range of view from one side to the other.

Side imaging fishfinders use different frequencies than other types. You will get sharpest images with the 800 kHz option, while the 455kHz option will provide the most range.

Side-imaging mode is the best way to read the information. The most recent details are at the top while older areas are at the bottom.

You Need to Know Information

The Information You See is Not Necessary Directly Below You

The screen does not necessarily show that it is below you. Sonar emits sound in cone patterns, so results may not be directly below you. This is not something your screen should mislead you about.

Sound does not travel in a single direction. It’s a wave that expands. The deeper the water is, the greater the range that your fish finder can scan.

Many scanners let you adjust the scanning angle to show more or less water. While a wide scan (above 40°) can be used to scan large areas and provide information about depth and bottom structures, a narrower scan will not give you as much detail. Because you can’t see as much below the surface in shallow waters, wider scans are more effective in shallower water.

A narrow scan is preferred in deeper water. A narrow scan setting is more common if you need to find fish below the boat or pinpoint the depth of the water below it.

Fishfinders Can Locate Other Objects and Have Blind Zones

Reflections of sound waves and other debris near the surface can make it difficult to get great results with your fish finder within the first meter of the device.

The scrolling of your Fish Finder does not mean that you or the fish are moving

The screen displays historical and current scans of your device. The SONAR will continue to display results even if you’re not moving. This is because the SONAR continuously sends sound waves and displays the results on your screen. If the SONAR is active, one fish might appear repeatedly.

Surface differences are more apparent in thicker, more colorful or dense results

If your results show distinct, solid lines, it is likely that you have a deeper bottom. A rocky bottom will show more clearly while a muddy one will produce weaker and thinner results. It is important to know this because different bottoms will affect your fishing techniques and ability to catch fish.

Fish are Arches

A lot of times, a fish will not be in your SONARs viewing area for the whole time. The fish will move in and out of your viewing zone or pass by your boat. The action creates an arch-like feature on your device.

This can help you to understand the fish on your screen.

  • An arch won’t occur if you aren’t moving. An arch will also be created if the fish is still and you are not moving over it.
  • If you have a fish that is under your device, it will show you a line and not an arch.
  • If the arch is full, it means that the fish went completely through your SONAR area.
  • If the fish is only able to pass through a portion of the zone, it’s likely that you will only see a partial arch or a narrow line.
  • It doesn’t necessarily mean they are big. A thick line is big.

Tips and techniques

Your first step to improving your fish-finding skills is to learn how to use your chartplotter and your finder together. When you can find exactly where they are even hours later than you last saw them, the blips and blurbs you see on-screen will mean a lot more. This can be done in a few ways. If you have a combo unit, the best way to do this is to have the screen split between chartplotter and fishfinder. If you don’t own a combo unit, or a fully-networked network, it’s time for an upgrade.

These systems allow the plotter and finder to communicate continuously, allowing them to scroll back in their finders and record the spot’s GPS coordinates long before you have passed it. This means that you don’t need to run for the helm immediately after you receive a strike. Instead, you can go back in your chartplotter and enter MOB, then record the spot’s coordinates. You can also go back in the history of the finder to record the spot if there is any mishap on-deck. The GPS will then know exactly where you were when the fish or structure was being inspected.

All those men who insist that you should not have all-in one units because if one fails, both will be out of commission. First, you will be disabled in any way. A fishfinder won’t help you find your way home if your chartplotter goes off-track. Having a chartplotter in case your fishfinder fails will make it impossible to fish blind. A handheld GPS is a great backup in these modern times. If you are upgrading an existing unit, you can leave the old fishfinder at your helm to have a backup sounder. In the best scenario, you will have a twin screen system. This means that even if one component of the system is down, you can still see the other.

Recording position isn’t the only way to improve your fish-finding abilities when you use these units in concert. Split the screen and use the chartplotter for clover-leaf patterns to surround the mark. This will reveal any structure or concentrations surrounding the fish.


After you have learned how to use the plotter and finder together, and are familiar with the history of the finder, it will become easier to zoom in on the bottom more often. You’ll learn a lot about what you are fishing in, and how the bottom type is determined by using the finder. One exception is when you are fishing in deep offshore waters. In these cases, the bottom composition may be more important than others. It is important to remember that the way it appears on-screen can be counterintuitive. Hard bottoms will have a thin bottom line while soft bottoms will show thick bottom readings. The sonar waves penetrate soft bottoms to a certain degree before being fully bounced back. It’s difficult to tell the difference in full-screen mode when there is water deeper than 30 or 40 feet. Zoom in on the last five to 10 feet of water to see which kind of bottom you are fishing on.

Zooming in on the fishfinder screen helps you see if this boat is on a hard bottom that has fish stacked.

A thermocline is another important aspect of your fishfinder’s potential. These are temperature barriers that separate layers of water. Fish often see them the same way as they see solid structures. They often look like broken readings on your screen and can be mistaken for baitfish. It will be obvious that it is a thermocline if it stays at the same depth for long periods. The position of hard returns can also help you identify a thermocline. For example, if you see broken marks at the same depth in blue on your machine and then see some red arches, it is likely that you are looking at large fish just above a thermocline. Tip: Set your baits at this depth.

Tuning Sensitivity

The video shows that today’s machines are capable of amazing automatic tuning capabilities. It’s important to trust this technology most of the times. However, there is one situation where you might want to reduce the sensitivity. This is when you are in extremely turbid water or water with thick planktonic and algae growth. This can often cause the finder to display a lot of clutter and fool it. You can then peak the transducer, and gradually reduce the sensitivity until the clutter is gone.

Another thing to note about auto-tuning is that it is almost never a good idea to add or increase filters to reduce the amount of surface clutter. They will reduce the finder’s sensitivity and it is not a big deal to lose a view of the first few meters. Are you sure that predators will happily swim a few feet under a moving boat? It’s unlikely. It’s not worth removing the clutter from the surface.

Let’s lastly talk about arches. Although it is true that arches can be created by fish with hard, good returns, there are a few variables you need to remember. Boat speed is the most important. Fish that are slow to move below the boat may appear as lines or blobs, rather than arches. Your finder is fine. To make a return appear as an arch, it must pass through the transducer cone. If it remains in one sport (more than or less), it will never arch regardless of how great the finder is or how large the fish. Don’t adjust the sensitivity or filter to make the fish arch.

Fish that pass through the cone of sonar wave will create an arch on their fishfinder screen. Static targets won’t.


Are you still unhappy with the results of your fishfinder? You can adjust or move the transom-mount transmitter to fix problems. I have found that fishfinders equipped with transom mounted transducers produce substandard results 80 to 90% of the time. The boat’s or powerplant’s turbulent action can completely ruin fishfinder performance. You need to adjust the transducer until you get a clean, steady flow of water.

Naturally, there are a lot of features and functions that are manufacturer-specific, which it wouldn’t make sense to cover here. These tips and techniques can be applied to any fishfinder. But if you want to get the most out of your machine, you need to go out fishing more often and spend more time on the water to learn about the specific features and functions.

Last Thoughts

Although fishfinders are not easy to use at first, it will become easier with practice. Before you go fishing, make sure you are familiar with the basics of how to use your device. And most importantly, have fun!

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.