How To Read A Fish Finder

Fishfinder technology has developed throughout time, making them effective for analyzing underwater topography and locating potential big fish arches and sites like drop-offs or underwater features like submerged trees, a structure, and wreckage.

They make it possible to identify schools of fish or individual fish with pinpoint accuracy. Mastering how to read a fish finder’s screen features correctly quickly becomes an issue many beginners experience.

Modern fish finders are miniature computers that use specialized software to convert sonar waves and generate a picture of what is happening beneath and around the angler’s boat. Because not every angler is technically aware, you can see why anglers become dissatisfied and believe they’ve wasted money.

Our guide will teach you about understanding fish finder images, what chirp sonar is, how to read sonar on a fish finder. By the end, you’ll have more insight into how to read a fish finder screen and use it to your advantage.

How To Read A Fish Finder

What Are the Lines On My Fish Finder?

When reading depth finders, it is quite common to see lines that don’t resemble shapes on the screen. When you see vertical lines on your screen, this means your sonar is suffering interference or crosstalk from another source.

Imaging sonar throws out waves, and depending on your fish finder, it could be up to a couple of hundred feet outward from your location. If another angler in the vicinity uses a comparable fishfinder with side imaging, their finder could be doing the same.

A sonar imaging from down imaging can also have a similar effect when the transducer cones collide in deep water depth and are harder to prevent by changing location alone.

If you have the option, switch the sonar unit’s frequency. Deeper sonars operate at frequencies of 290 and 90 kHz; therefore, lowering the frequency of one device will significantly reduce erroneous readings.

What Do the Colors Mean On a Fish Finder?

It can be easy for an angler to understand the fish finder basics, but once it translates the sonar image on their screen, it can look like a jumble, and identifying separate items can be hard.

While you have side imaging and down imaging, this won’t affect how the system translates the data returning from the sonar beam sent into the water column.

When learning how to read a fish finder, Lowrance, Garmin has unique ways of setting up their finders, yet once you learn how to read fish finders from key manufacturers, the steps are roughly the same.

For example, using a Garmin fish finder, you can see how to read sonar fish finder and see what fish and something else are.

Here’s how to understand, what do fish look like on sonar? On said fish finder, if you enable the fish symbol settings (Fishfinder 300c/ 400c), you’ll see how to identify fish on a fish finder as you have two colors, blue and orange.

What does a fish look like on a fish finder? On this fish finder, the color of your fish icons stems from the dual-beam transducer since this determines the beamwidth.

In a narrow beam falling into the 200kHz frequency, you’ll see orange fish appear. So, fish arches from a down imaging sonar cone are going to be bunches of orange. Target separation can play a huge part in this, as smaller fish could appear as a cloud. (Find the Best Fish finder for Kayaks)

Bluefish will show up in the 50kHz frequency’s Wide beam, which is more likely to be side imaging in shallow waters.

Because of the ways dual-beam transducers work, both blue and orange fish will appear if a wide beam is selected.

Only the narrow beamwidth is output when the transducer narrows. When the transducer is set on wide, it will cast combinations of narrow and wide beams.

Based on the color lines you have set; the hard bottom can be seen as bright yellow color and a broader band of blue below a light or bold line.

The yellow-blue returns fade into orange once you pass the hard bottom to a softer and mucky bottom to deliver an accurate representation.

Understanding fish finder images

How to Read Fish Finders?

Here is a breakdown of areas that can get confusing when trying to work out what do fish look like on a fish finder.

Depth, Speed, and Temperature

Fishfinders offer much more than scanning for fish when you’re in your kayak.

To grasp and read a fish finder, you must first grasp how it works. The transducer, or bottom section of the fish finder positioned in the water, emits sonar waves.

The waves bounce about and return to the transducer, where the transducer’s speed, distance, and rate of return are measured.

Your transducer converts raw data into visual data, which is typically thick, with colored lines and arches. These lines are put at various depths, and the depth of where a fish appears on the fish finder can determine its location.

Depth Finder

The first thing to know about fish finders is the depth finder. Most fish finders contain a depth sensor on their transducer so that you can determine the water depth underneath your boat.

The depth of the water tells you about fish in the area, what to expect beneath you, and so on. The depth is usually shown in the upper left of the screen, and the depth should be accurate. You’ll also find they are often in meters, not feet depending on the fish finder model purchased.


The water temperature is usually seen underneath the depth reading and can be useful for finding certain fish species—some fish like warmer water than others.


The speed sensor is another useful feature on most fishfinder displays. On your fish finder, the speed sensor displays as a speedometer.

Echo Return and Color

Now you would need to know how to start identifying things from your fishfinder results.

You can get some fishfinder using grayscale or black and white, while the better ones are often color models.

Infra-red echoes return from underneath the water to the transducer, and it is the strength of such echoes that determines an object’s density and hardness: the stronger the return echo, the darker or stronger the fishfinder display color.

The bottom of any water body, such as the ocean, would typically be the darkest object encountered. The bottom of a lake or river could be thick or thin.

A faint line shows a softer ground material like clay, and then you’ll find a bolder line that shows a less porous bottom material. (Find the Best Kayak Fish Finder)

Fish Finder Screen Data

Once you understand how color can represent information, you can interpret your fish finder screen results.

Set up your fish finder, then move slowly around the area you’re fishing. Monitor the fish finder to be accustomed to the speed you’ll be comfortable with, as you’ll need to watch the image on your fishfinder screen as you troll around in your boat.

Because of how sonar waves are emitted underwater and where the transducer is mounted, some fish finders perform better at slower speeds.

A regular speed can be better for most fish finders, so be used to having your fish finder mounted on your boat, controlling the screen, and traveling at the optimum speed.

A Fishfinder display features results shown right to left as they can, which is the opposite of how you read. On your fish finder’s display, recent results are on top and the oldest to the left.

If you are stationary, the images from the sonar cone should also be still, although if you’re moving, the fish finder will scan what’s beneath the transducer in a vertical beam to the bottom and what you’ve passed on the left side. (Find the Best Kayak Lights For Night Fishing)

Learning how to read a fish finder

Reading Fish-ID

Knowing how to read a fish finder can be the most difficult part. You know how to use color to see if something is under or behind your boats, such as a bed or a structure.

Now you must look at how to understand things like fish, structure, schools, and other fish-holding objects on your fishfinder. Once sonar waves return to the transducer, a fish finder will display the results in one of two ways.

The fish finder can show raw data, or software converts the lines and arches into small, distinguishable icons based on what the fish finder can see. The first information display for fish finders is Fish-ID technology, which generates the fish arches.

This technology converts raw data into a user-friendly display. You’ll notice smaller fish icons with fish of various sizes, which vary depending on the size of the detected fish.

It uses various icons for rocks, plants, and your schools of fish, though this will depend on the fishfinder model. A Lowrance finder can appear different from others, such as Garmin.

When using some Fish-ID systems, you can, in theory, check the icon or fish arch to determine if it is a big fish or smaller fish and check the depth of the icon and cast.

It is worth noting, a Fish-ID enabled fish finder can often display a school of fish as rocks or plants, and many anglers often prefer to disable having fish symbols show on the screen and carry out the fish interpretation themselves.

How to install a fish finder