How to find fish using Raw sonar screen mode

There are 2 ways you can detect fish and determine their size using the Deeper Sonar PRO and CHIRP models: by using Fish Icons or Detailed sonar screen mode (having Fish icons OFF).

Using Fish Icons method

Fish Icons option is the easiest way to locate fishes, and something that can be used if you don't have experience in reading the sonar screen. However, it is less accurate.

When Fish Icons are enabled, special algorithms will analyze the sonar screen and mark ultrasound reflections from fish with fish icons. There will be 3 different sized fish icons according to the discovered fish sizes. If you choose to use this option, here are the best-suited settings of your Deeper sonar:

Sonar display: Detailed (Raw)

Beam angle: Any

Fish Icons: ON

Sensitivity: 70-90%, but can be reduced if the water is murky, or if you're targeting big fishes only."

 Considering that fish detection is handled by software algorithms, Fish Icons function can sometimes make mistakes in fish detection. We recommend turning off Fish Icons and using the second method described in this manual.

ⓘ Please note that it is impossible to determine the exact size of the fish using any kind of sonar technology - this is related to how all sonars work and ultra-sound physics. So, you should look at different size of fish icons as an approximate evaluation of the size of the fish, but not as exact measurement. It is impossible to say that Big fish icon means that the fish underneath is more than 20 or 35 cm long. But when you see a big fish icon - there is a very good chance that the fish is actually big.

Detailed sonar screen mode (Fish icons OFF - recommended)

Recommended option is to disable Fish icons and look at the real sonar readings, which is a more advanced method, but more accurate at the same. This is a recommended way of locating fish. If you will turn Fish Icons off, you'll see that fish in sonar readings are displayed like arches or lines. The thickness of those lines/arches is the indication of how big the fish is.

Recommended settings:

  • Sonar display: Detailed (Raw)
  • Wide beam (47°/55°) is good for quickly scanning larger areas and getting general information on fishes, depth and bottom structure, but the accuracy and detail will be lower. You will not be able to accurately determine the size the fish using Wide beam, but due to a large area covered by the beam, you'll be able to locate the presence of fishes faster (for example, if you're looking for schools of bait fish).

Note: Wide beams are not suited for shallow water scanning. If you are scanning waters shallower than 2-5 meters (7-16 ft), we recommend switching to Narrow beam.

  • Narrow or Middle beam (7°/15°/20°) is much more accurate when determining the size of the fish, so if you see a thick arc or line when using this beam - the fish is definitely big. Narrow beams cover a smaller area, so it may be harder to locate the general presence of fish.

Note: Narrow beams are very sensitive to water disturbances, so you may see visual artifacts if there are a lot of waves.

  • Fish Icons: OFF
  • Sensitivity: 70-100%, but can be reduced if the water is murky, or if you're targeting big fishes only.

ⓘ When locating fish, use the Wide beam first to find the general location of fish, then switch to a Narrow beam and scan that area a few times to get the exact location and the size of fish.

ⓘ When using Wide beam, fish arches/lines will look much thicker, compared to when you use a Narrow beam. It is better to use Narrow beam for a more precise evaluation of the fish size.

Some important things to remember about fish arches:

  • You will only get arches from moving fish (or if your sonar is moving over them).
  • If your sonar and the fish are both stationary, you will see a line, not an arch.
  • You will only get a full arch if the fish moves through the full sonar beam.
  • If a fish swims through part of your cone, it will show as a half-arch or a thick dash – look out for these.
  • Longer lines can indicate a more active fish that moves rapidly under the sonar cone, while shorter arches may indicate that fishes are less active


Examples of fish scans

On this scan, you can see a catfish chasing a bait during vertical jigging. You can see that the signal from the catfish contains red and yellow colors - which means that the catfish is quite big.

Model: Deeper CHIRP+
Beam: Mid
Color mode: Day
Sensitivity: 90%


Big pike is actively moving between 2 and 3 meters of depth. You can see two big arches on the screen, but in reality, it's the same pike which has entered and left the sonar beam once, and then entered it again. Red and yellow color on the arch is indication that it's big.

Model: Deeper PRO+
Beam: Narrow
Color mode: Day
Sensitivity: 80%


In this scan you can see multiple predators (1) who are trying to attack a school of smaller fish (2) while the school is trying to evade the attack. A fish arch from the predator has an upwards shape which indicates that it is moving towards the school of baitfish. The school of baitfish synchronically tries to avoid the attack by swimming down to the bottom, but one predator is still chasing it (3).

Model: Deeper CHIRP+
Beam: Mid
Color mode: Day
Sensitivity: 100%


Zander (walleye) on the bottom of a hole. You can see a small arch of a zander (1), and hardly visible smaller arches above it - those represent smaller fishes.

Model: Deeper CHIRP
Beam: High
Color mode: Day
Sensitivity: 100%