How Does a Fish Finder Work? A Detailed Explanation

Are you curious about how does a fish finder work exactly? If you’re an avid angler, a fish finder can be an incredibly useful tool for improving your chances of catching fish.

In this article, we’ll delve into the details of how fish finders work and provide a thorough explanation of the technology behind them and how they help you locate fish. So, let’s dive in!

What is a Fish Finder?

A fish finder is an electronic device that uses sonar technology to detect fish and other underwater objects. It emits a sound wave that travels through the water, and when it hits an object, it bounces back to the fish finder. The device then measures the time it takes for the sound wave to return, and it uses that information to determine the depth, location, and size of the object. An example of a Humminbird SOLIX 12 fish finder given below.

Humminbird SOLIX 12 Fish Finder

The Parts of a Fish Finder

To better understand how a fish finder works, let’s take a closer look at its main parts:


The transducer is the heart of the fish finder. It sends out the sound waves into the water and detects the echoes that bounce back. The transducer is usually mounted on the bottom of the boat or kayak, and it should be in direct contact with the water for optimal performance.

Humminbird XM 9 HW MSI T HELIX Temperature Transom Mount Transducer
Humminbird XM 9 HW MSI T HELIX Temperature Transom Mount Transducer

The transducer’s size and shape can affect its performance. A larger transducer can emit more powerful and accurate sound waves, while a smaller one may be easier to install and more portable.

Display Unit

The display unit is where you can view the information collected by the transducer. It displays the depth, location, and size of fish and other objects detected by the fish finder. The display can be a standalone unit or integrated into other fishing equipment, such as a GPS or chart plotter.

The display size and resolution can vary depending on the model and manufacturer. A larger display can make it easier to read the information, but it may also be more expensive and consume more power.

Power Source

A fish finder needs a power source to operate. Most fish finders use a 12-volt battery, which can be rechargeable or disposable. The battery’s size and capacity can affect the fish finder’s runtime, so it’s essential to choose a battery that can provide enough power for your fishing needs.

Some fish finders can also connect to the boat’s power supply, which can be more convenient and reliable than using a separate battery.

Transducer Mount

The transducer mount is where the transducer is attached to the boat. It can affect the transducer’s performance and stability, so it’s crucial to choose a mount that can keep the transducer in the correct position.

There are several types of transducer mounts, including a through-hull mount, a shoot-through mount, a transom mount, and a trolling motor mount. Each mount type has its advantages and disadvantages, depending on the boat’s design and the fishing conditions.

Cables and Connectors

The cables and connectors connect the transducer and the display unit. They transmit the signals and power between the components. The quality and length of the cables and connectors can affect the fish finder’s performance and durability.

It’s essential to choose cables and connectors that are compatible with your fish finder and boat, and to protect them from water and physical damage.


There are several accessories that can enhance the performance and convenience of your fish finder. Some of the most popular accessories include a transducer shield, a GPS antenna, a temperature sensor, a speed sensor, and a power cord extension.

Each accessory can provide additional functionality and information to help you locate and catch more fish. However, they can also add to the cost and complexity of your fishing equipment.

By understanding the main parts of a fish finder and their functions, you can choose the right fish finder for your fishing needs and make the most of its features.

How Does Sonar Work?

Fish finders use a type of sonar technology called CHIRP (Compressed High-Intensity Radiated Pulse). CHIRP emits a range of frequencies that allow the device to distinguish between different objects underwater, including fish and vegetation.

The sound waves emitted by the fish finder travel through the water until they hit an object, like a fish. The sound wave then bounces back to the transducer, which measures the time it takes for the sound wave to return.

The fish finder then uses that information to determine the location, depth, and size of the fish. The device displays this information on the screen in real-time, allowing anglers to adjust their fishing strategy accordingly.

Interpreting the Display

When you’re using a fish finder, the display can be overwhelming at first. But with a little practice, you’ll learn how to interpret the information to locate fish more easily.


The depth of the water is displayed on the top of the screen. The transducer measures the distance from the surface of the water to the bottom of the lake or river.

Fish Arches

When a fish swims through the sound wave emitted by the transducer, it appears as an arch on the display. The size of the arch corresponds to the size of the fish.

Fish Symbols

Some fish finders use fish symbols instead of fish arches. The device identifies the fish’s size and displays a fish symbol on the screen.

Bottom Composition

Fish finders can also detect the composition of the lake or riverbed. This information is displayed on the screen and can help you determine if the area is suitable for fishing.


Fish finders are an essential tool for anglers looking to locate fish and improve their catch. They use sonar technology to detect fish and other objects underwater, and the information is displayed in real-time on a screen. By understanding how fish finders work, you can make the most of this technology and enjoy more successful fishing trips.

Read more: Learn How to Fish Like a Pro

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