How to Use and Read a Fish Finder – Complete Guide for Beginners

You can’t enjoy fishing if your trips in the water prove to be unsuccessful with no or little catch every time. To avoid such experiences, you need the right equipment to increase your catch. One of important instruments is the fish finder which helps you locate fish and see the water bottom. However, you’ve got to know how to read the fish finder for you to use it. This is because the screen shows signals that can be confusing if you’ve never used a fish finder before. Here’s a comprehensive guide on reading a fish finder and understanding the signals on the screen.

Understanding Fish Finders basics

Before going deeper into how to use a fish finder effectively, it’s best to know the fish finder basics first. Read on and understand the main features you should consider while reading a fish finder screen.

·         About sonar

All fish finders have transducers that release sonar waves into the water. Sonar stands for sound navigation and raging. It bounces off on underwater objects like fish and shows their size, location, and shape back to the fish finder. After that, you get to see some information on your fish finder’s screen which you should read to identify fish, vegetation, or rocks underwater. Through this, you’ll be able to know fish hiding place, helping you strategize your fishing well.

·         The transducer

Transducers work together with sonar by releasing waves that detect what’s in water and send the data back on the fish finder’s screen. Some of the transducers come with the fish finders, while others you buy separately. For it to work perfectly, ensure you install it well and it is fit for your boat.

There are three types of transducers, and each comes with its unique features. They also have varying powers and frequencies, so you get one according to your fishing needs. When you want to get a transducer, it’s advisable to consider your fishing depth.

The fishing depth, which in other terms is ping power and is measured in watts. Note that the bigger the watts, the deeper you’re fishing. For freshwater fishing, you should use a transducer of 300 watts ping. If you love fishing in salty water, go for the one with a watt ping of between 500 and 1200.

You can get a transducer of either low or high frequency. When using the lower frequencies, you should fish at a slower speed to get accurate information. Low frequencies transducers are best for deep water fishing and help you see maximum depth.

On the other hand, high frequency is ideal for identifying fish hiding in structures because of its high resolution. With it, you can see smaller fish, move at higher speed, and get clear details of objects underneath your boat.

·         Chirp on fish finders

Chirp, which is a technology that has been in use for some time now, allows fish finders to see individual fish at high resolution. It works with sweep frequencies, unlike the standard sonars, which use single or double frequencies. However, they’re a bit expensive although it’s worth the money.

Factors You Should Consider Before Buying A Fish Finder

  • The kind of boat mount you want to use. You can either opt for a transom mount which is ideal for smaller boats since they need small fixing space. Or hull mount, which best suits larger boats which allow you to choose the mount location. Another one is the in-hull mount which is good for fiberglass hulls.
  • You should also consider the fish finder features like a GPS, transducer, and display monitor, although they also come separately.
  • Another thing is the depth or the bottom the fish finder can cover. This majorly relies on its power and frequency. A high power translates to a strong sonar signal, which means the transducer can cover deeper depths.
  • The size of the boat you use for fishing.

Understanding How to Read A Fish Finder

After understanding what sonar fish finder is, it’s time to know how to read the fish finder screen correctly, thus allowing yourself to locate fish accurately.

Those of you who have never used a fish finder might be wondering, what do fish look like on the fish finder screen? Well, it varies and depends upon multiple factors like your fish finder model and whether you are doing a deep scan or side imaging. The easiest way you can do this is by using fish ID’s technology which uses information from sonar to identify which object is fish, then send it to your fish finder screen. You’ll see fish icons on the screen showing their type, location, or size through this technology. Although fish ID will give you accurate information, it might confuse vegetation for a school of fish.

The hardest to read fish finder sonar image is through using arches and raw data. Even though doing this is hard, it gives more accurate data.

With it, you’ll know:

·         Fish Size

On the traditional fish finders, the fish arches will appear as curved lines. Look if the width or arch is full or half to know the size of fish underwater. A thick line or arch width indicates big fish since a bigger fish sends back strong waves. But at times, smaller lines can be a sign of big fish, depending on their location. For example, trophy fish can show up as half-fish arch if they swim in a smaller part of the sonar cone. This means a long fish arch shows when a fish swims slowly through the sonar cone.

You can also know the fish size if the boat and fish are still through the length of the fish arch, although you’ve got to adjust for the water depth.

·         The water depth

You can also know the water depth through reading sonar images on display. Knowing the water depth is crucial in determining the kind of fish found in a certain location. If you see fish icons or arches 25 feet deep in the water like in Michigan lake, it can indicate the presence of summer smallmouth. To know where to read the water depth on the fish finder screen, look at the top left part of the screen. Note that this position varies with the model you’re using. Also, the water depth reads in meters or feet, depending on the model.

·         Reading water temperature

If you want to read the water temperature, check on the lower part of where there’s water depth. Knowing the water temperature will help you in species targeting, going by their preference of either cold or warm water.

·         Can you read the speed of your boat on a fish finder?

Yes. Most fish finders have inbuilt speedometers that display the speed of your boat on their screen. It will help you control your speed where necessary. For example, you can use it to determine your rate while reading the fish finder. Remember, there are instances where you have to maintain steady speed to read the fish finder and get quality images. It’s advisable to use a trolling speed of between 1 and 4 miles per hour to allow your fish finder to accurately locate what’s under the boat.

·         Reading fish finders with either color or grayscale display on the screen

2D sonar fish finders have either grayscale or color display on their screen. Reading color fish finder displays are the best and easiest way to see what’s underwater. With color, you can differentiate between structures and fish. You’ll also see different types of fish and the hard bottom surface.

If you see brighter colors, that’s an indication of soft objects like weeds or clay. This is because lighter things send weaker signals. For denser objects, your screen will have darker colors because of the strong signals it returns.

Reading the grayscale screen display is never easy since you can’t differentiate trees from fish. However, it’s ideal for checking the bottom hardness. If you see a darker screen on grayscale, that’s the presence of dark objects. The lighter materials give a lighter screen.

Note that in grayscale, a white specks suspension on the screen can be a signal of fish. Also, having a cluster of white specks can be a sign of big fish, while a solid mass shows bottom growth like weeds.

·         How to read the presence of baitfish

If you want to know if there’s baitfish under your boat, you’ve got to be careful. This is because they announce their presence through dots, small lines, or dashes. But seeing a school of fish isn’t hard since they appear big, like big round balls suspended on the water.

·         Reading data display sequence on a fish finder

You can read data display sequences on a traditional 2D sonar screen. Note that you should read the information from right to left. Largemouth Bass will appear as white or light-yellow beans on a standard fish finder. They like distancing themselves from each other, although not heavily clustered. The smaller bass love to cluster and resemble blobs while the bigger ones maintain their space.

Note that if you’re using a fish finder with down imaging, the information will flow from right to left across the screen. Down imaging is ideal when you’re using fishing reveal technology. In case of side imaging information appears from the top of the screen to the bottom.

How to Use Fish Finders to Locate Fish in their Various Hiding Structures

Finding fish from their hiding places in water is never easy, but with a fish finder, that’s a walk in the park if you use it well. To achieve this, ensure you pass the fish finder severally in the area to see them in their hiding structures. Make either two or three passes to get more accurate data.

You can also use a dual-frequency fish finder by combining both traditional sonar and down imaging. Doing this will give you a clear view but ensure you use a low-frequency fish finder before using a high-frequency fish finder to get their hiding place.

Fish reveal technology is also good for this purpose. It allows you to look at a split-screen of traditional sonar and down imaging. Lowrance is one of the well-known fish finder brands with such technology. It functions like fish ID, although it allows you to see objects more clearly and in detail.

Another way of finding fish in their hiding place is through adjustable contrast, a Lowrance technology that lets you adjust the contrast in the menu search. It gives quality clear images helping you see fish from their hiding in certain structures like ledges. Since the information display sequence is similar for all the imaging options, it means they work together. Also, the data flows from right to left, so seeing hiding fish is easier.


Reading a fish finder for the first time is never easy, but you can do that with fewer challenges after going through this guide. Reading it with ease is possible once you understand fish finder basics and know how they work. Since fish finders have automatic settings, you won’t have difficulties fine-tuning it.

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