How Fish Finders Work And How To Read Them


Anglers who are tired of going home empty-handed after a long day of fishing often turn to fish finders for help. These nifty gadgets are a practical and effective way of finding fish, so much so that many anglers never leave the docks without one. Needless to say though, not knowing how to use a fish finder can hinder your fishing success. And let’s admit it, there are still a lot of anglers who aren’t tech-savvy and find manipulating these gadgets rather intimidating. To make the problem worse, there’s a wide variety of fish finders in the market with varying setups and configurations. If you are confused about how to use and how to read a fish finder or are wondering “how does a fish finder work?” this guide’s for you.

How Fish Finders Work

Before we get started with reading fish finders, let’s first take a look at what they are and what they do. Basically, fish finders are small computers with special software that shows you what’s under the water, namely the landscape and the fish. Fishfinders are typically sold as a kit that includes a display unit and a transducer, though some of them come with other accessories.

Screen/Display Unit

The screen or display unit is simply what its name suggests, a screen that displays the data gathered by the transducer. It’s available in a variety of sizes from small 3.5 inches to larger 16-inch screens. More often than not, a small display unit will be enough for most anglers, though of course, a bigger screen is much better since it is capable of displaying more data as the screen can be split, allowing you to view more information at the same time.


The transducer serves as the eye of the whole fishfinder system as it is responsible for detecting what is under the boat. To do this, the transducer sends sonar waves down into the water which then bounces back and returns to the transducer. The transducer then reads the speed, distance, and rate at which the sonar waves return and interprets these raw data into visual data (usually in the form of thick colored lines and arches) which is then presented through the screen or display unit.

GPS and Chartplotters

Many fish finders have GPS capability, allowing you to track your position on a map. Nowadays, fish finders are equipped with an internal GPS receiver, but there are external receivers available for units that don’t have internal GPS. GPS is a very useful tool for every angler, especially those who like fishing in open water. In fact, many anglers always carry and use a GPS when fishing and use it for navigation and scouting for fishing areas. Besides, they have chart plotters that allow you to mark waypoints so you can return to those exact locations at a later time.

Related Review: Fishfinder Gps Combo

Other Features

Depending on the brand and model, fish finders can have a variety of features and options that can be helpful for anglers. For instance, some fish finders allow anglers to create custom maps, which is helpful if you’re fishing in unfamiliar waters. All you have to do is to turn the device on and move across the water’s surface (be sure to cover as much ground as possible) and the device will start building a map using the data it captured.

How to Use Fish Finders


Fishfinders can be basic or complicated. Either way, it takes some learning curve before you can use them properly and effectively. If this is the first time you’ll be using a fish finder, take some time to learn how to use it before you hit the water.

1. Read the Manual

Let’s face it, very few people read the manuals that came with their devices, whether that’s a fish finder, a phone, or any other appliance or gadget. When you get yourself a new fishfinder, do take some time to go over the manual. It contains everything that you need to know about your device and how to use it. Sure, you can just toss the manual aside and learn about your fishfinder as you go along. However, people who do this often waste a lot of time trying to figure out how to use their fish finders instead of actually doing some fishing when in the water.

2. Mount the Fish Finder

Mount or install the fish finder and the transducer in your fishing kayak or canoe. Depending on the type of fish finder you have, you can do a transom mount, a trolling motor mount, etc. Again, refer to your owner’s manual to determine the recommended mounting style for your particular model. Some fish finders do not come with a mounting system, so you may need to buy a fish finder mount separately.

3. Check Power and Turn the Fish Finder On

One thing you’ll want to check is the power. Some fish finders are rechargeable and others will require batteries as a power source. If your fish finder came with the former then make sure that it’s fully charged before you turn it on, and in the case of the latter make sure that you install fresh batteries first.

4. Familiarize Yourself with the Display

For you to catch any fish utilizing a fish finder, you’ll need to understand how information is displayed on the display screen. Depending on the make and model of your fish finder, a variety of information will be displayed on the screen. There’s the depth finder, the water temperature, and the speed sensor. You also need to familiarize yourself with the colors shown by the fish finder. For instance, the bottom of the lake or pond, or river will often be shown as a thick line or a light line. In the case of the latter, it means that the floor or bed is a softer ground material like clay, whereas, in the case of the former, this means that the material in the bottom of the river is harder and less porous. Also, note that fish finders, in general, will display data from right to left, with the most recent data sensed by the transducer appearing on the far right side of the screen and the oldest being all the way to the left.

5. Configure the Settings

With the fish finder on, go to the “Menu” tab and configure the settings according to your preferences. However, do this step only if you are confident about using your fishfinder. Otherwise, you should leave the pre-programmed settings as they are and just tweak them after you get to test your fish finder in actual water. That said, let your fishfinder run in “automatic mode” first and see how it responds. If you’re happy with the results, you may want to leave the settings as is or configure them to fit your preferences.

6. Adjust the Sensitivity

Once you’ve cruised about with your fish finder in “automatic mode” and played a little bit with the settings, you can start configuring the fish finder’s sensitivity. In many cases, you’ll find that you need to adjust the sensitivity settings more often than usual, matching it to the conditions of the water you plan to fish in. For instance, if you’re going to be fishing in shallow waters, you’ll want to adjust the sensitivity settings to higher frequencies. On the other hand, if you’re fishing in deep waters, then you’ll want to set the sensitivity settings to low frequencies. If this is your first fish finder, you may find it difficult to get the sensitivity settings right. But then again, with some practice and patience, you’re bound to find the perfect sensitivity settings that will match the conditions of your fishing destination.

7. Set Your Fish ID Setting

Another feature that you’ll want to pay particular attention to would be the Fish Identification feature. As the name suggests, this feature will allow you to identify the type of fish in your fishing area. This is a pretty helpful feature when you’re targeting a particular fish, but is likewise helpful if you aren’t familiar with what fish is available in the area. Some fish finders also have icons for plants and rocks and show measurements regarding the depths of these objects. Data such as these, along with information about where the fish are holding, will help you to better plan where to cast your line. At this point, you should also play with the zoom settings of your fish finder since this will tell you a lot about the area you’re fishing in.

Using and understanding all the data presented by your fish finder will take some time to get used to. And in many cases, anglers who are technophobic or aren’t very tech-savvy might feel overwhelmed with all the information presented in the display unit. However, don’t get discouraged and continue learning more about your gadget. In many cases, fish finders will be your best friend while you’re out in the water and in search of that trophy-sized fish.

Globo Surf Overview

Fishfinders come with a variety of features and learning how to use them all effectively can be quite overwhelming and even intimidating. However, the steps outlined above about how to read a fish finder should apply to most fish finders available in the market nowadays. But reading those tips alone aren’t enough. The only way to learn how to fully utilize the different features of your fish finder is to get out there and spend more time on the water with it. Just keep in mind that the only way to actually get the fish is by casting your line into the water, so don’t get stuck in front of the screen.

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Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!