How to Read Fish Finder Screen – All You Should Know

Most people are familiar with modern machinery, but still, don’t know all functions. This circumstance also happens when an angler is purchasing a fish finder for the first time, you can see through their eyes when they ask the seller: “Is this difficult to use?”

Manufacturers understand this issue so they produce the basic fish finder with only three buttons and a few simple functions that anyone can use. However, professional anglers are given multiple advanced options, and here are 11 basics techniques on how to read fish finder screen.

How to Read Fish Finder Screen: Speed Sensor

Although in the ideal environment we move quickly and find fish easily, the reality is different. When we are not moving, the screen show for more details, but the instrument has its limits.

For example, at a depth of 30m, images on screen show depth of 10, or 12 or 15 centimeters. Despite the fact that it is a great feature which helps us see all the details of water bottom, the more we move, the more difficult it is to see a clear image.

The maximum speed allows us to see fish clearly is from 5 to 6 km/h. In good conditions, we can increase the speed to 7 or 8 km/h.

Wave’s speed

Wave’s speed changes in the different environment. In water, waves propagate with the constant speed of 5267 km/s (or 1463 m/s), so the fish finder operates at this speed. However, the water wave is 4.5 times as fast as the air wave, and that is the reason why you don’t know how to read fish finder screen accurately when it is out of the water.

Most of the fish finders are adjusted to be read precisely at the depth with wave speed of 120 km/s. It can be read faster when you slightly lean it forward 2 to 3 degrees and less than 1 degree when on the boat.


Some fish finder results show the black and white screen. And most received signals will appear as light grayscales. The stronger signal returns, the darker color displays on the screen. What important is that users can adjust signal by themselves.


Image source: BoatUS

The color screen also works on that basis. A Strong signal is usually red, followed by orange, yellow, green as it fades and light blue represents the weakest signal.


Wave pulses are measured in kilohertz (kHz), as 1 kilohertz is one measurement unit of wave expressed by thousands of pulses in 1 second. Shortwave pulses are called rhythm and transmitted at different frequencies, depending on uses.

High frequency likes 455 kHz gives more details and wider coverage, but it is not useful in the deep water. 200 kHz frequency is more common as it gives effectiveness in deep water with clear images on the screen. Low frequencies from 50 to 83 kHz are good for transmitting to great depth though some details will disappear or get blur.


A fish finder can read and give detailed images from 100, 200, 300, 500 or 1,000 meters. What will happen if we are at deeper depth using a fish finder which can measure around 200 meters? The instrument still works, but the signal is reduced slowly because it cannot transmit strong enough waves and receive responses at that depth.


Image source:

If you keep moving, the screen will lose signal and get it back again when the boat goes into 200 meters. Depending on different types of the fish finder, it cannot show us images at great depth, in fact, it only shows the numbers, or even disappear when we go extremely deep.

Water temperature

Water temperature underneath the depth reading on the screen will help you locate species of fish, and some prefer cool water while others like warm environments.

Signal beams

Signal beams are transmitted at large or small amounts, therefore, giving us options. A wide signal beam has extensive coverage of one large area. However,  it does not show many details and clear images on screen because of giving too much information at one time.

By using wide beam signals, we can see a lot of fish, but simple water bottom structure. On the contrary, the small signal beam only gives us clearer images in small area. Therefore, we see less fish, but clearer bottom structure.

Nowadays, many manufacturers sell fish finders which have both small and large signal beam or special types transmitting a bunch of different signals beam at once.

Screen resolution

Each tiny square on screen represents one pixel. Vertical pixels give clarity and details for a user to distinguish individual signals while horizontal pixels are subsidiary. Users need to understand information on the first vertical line at the bottom right on screen because it says exactly what is happening under the boat.

Screen resolution

Image source: WaterGearLab

When vertical lines appear and move from left to right, they represent what was in the past and no longer exists. For example, 40 vertical pixels lines mean 39 of them show what was detected and passed when the boat is moving forward. Available fish finders on the market usually have 160 to 480 vertical pixels.


A fish finder has a self-regulating program’s system for people who do not like to change the program or do not understand about it. Conversely, if you want the instrument to be more powerful and more efficient, use the zoom for clearer images. Then gradually increase the sensitivity for more pixels appears on the screen.

Water bottom structure

With a fish finder, we know if our boat is on hard or soft bottom areas depending on the gray color on the screen. When signal beams are transmitted to the bottom, there are a large number of responses. Yet, others will be lost or sucked away. The gray background appears on the screen means the boat is on the soft muddy bottom. And red means the boat is on cobblestone area.

Water bottom structure

Image source: SPQR Moneta


This function transforms raw data into the simpler interface. The screen shows fish icons with different sizes, depending on detected fish. However, according to most anglers using a fish finder, you should not use the fish-ID way too dependable. The display screen often shows you fish icon when it finds any similar shape. For examples decaying logs, leaves, rags, or even plastic bags floating in the water….

To sum up, take the time to read the instruction carefully or look up on the internet before using fish finder. That way, you will have lots of valuable information to use this instrument properly.