How to Read a Fish Finder Screen

By Emmett Porter

A fish finder screen can look like a confusing mix of colors and shapes, but once you learn to read the sonar display, it becomes a reliable tool for locating fish and underwater structure. The screen acts as a scrolling history: new data appears on the right and moves left, showing what the transducer has passed over. This guide explains the key elements of a traditional sonar view, drawing on the Garmin STRIKER Plus owner’s manual, and shows how to adjust settings for a clearer picture.

The Sonar History and Depth Scale

In the traditional sonar view, the right side of the screen shows the newest returns, and the image scrolls to the left. The Garmin manual describes a range scale along the right edge that indicates the depth of detected objects. The bottom of the body of water appears as a strong, continuous line. Above it, suspended targets, often fish, show up as marks or arches.

You can adjust the depth range to focus on a specific water column. The manual lets the device adjust the range automatically based on depth, or you can set it manually; with a manual range, the bottom stays on the screen as long as it is within the range you set. The zoom options add Bottom Lock, which locks the screen to the water bottom.

Reading the Bottom Line and Structure

The bottom line tells you more than just depth. The Garmin manual’s Edge setting highlights the strongest signal from the bottom to help define whether the bottom is hard or soft. The A-Scope, a vertical flasher on the right edge, expands the most recent returns and, the manual says, can help with detecting fish close to the bottom. For a more detailed picture of structure, see our guide to sonar types, including Garmin’s ClearVü and SideVü scanning views.

Fish Arches and Why They Look That Way

Fish suspended in the water column often appear as arches, not fish‑shaped icons. The Garmin manual notes that wider sonar beam widths generate larger arches, making them easier to spot. Boat speed and scroll speed also affect how targets are drawn. A higher scroll speed shows more detail while moving, and a lower speed keeps the image on the screen longer. The Auto scroll speed setting matches the boat’s speed over ground so targets are drawn with the correct aspect ratio and look less distorted.

Fish Symbols and Their Limitations

Many fish finders, including the Garmin STRIKER Plus, can display suspended targets as fish symbols instead of raw arches. The manual’s Appearance menu lets you choose to show symbols alone, symbols with depth information, or symbols overlaid on the traditional sonar background. The manual describes this setting as how the sonar interprets suspended targets, so a symbol is the unit’s interpretation of a return, not a confirmed fish. Showing symbols with the background sonar lets you compare the icon with the raw returns behind it.

Gain, Sensitivity, and Surface Noise

The gain setting controls how sensitive the sonar receiver is. According to the Garmin manual, increasing the gain shows more detail, while decreasing it reduces screen clutter. You can let the device set gain automatically: Auto High displays weaker returns with more noise, Auto Med gives a moderate balance, and Auto Low shows only the strongest returns. For manual control, the manual suggests increasing gain until you see noise in the water column, then backing it off slightly.

Surface noise, clutter near the top of the screen, is caused by interference between the transducer and the water. The manual’s Surface Noise setting hides sonar returns close to the surface to clean up the display. The TVG (Time‑Varying Gain) control also reduces surface noise and can reveal targets near the surface that would otherwise be masked.

Scroll Speed and Image Quality

Scroll speed determines how fast the sonar image moves across the screen. The Garmin manual explains that a higher scroll speed shows more detail, especially when trolling or moving, while a lower speed keeps information on the screen longer. The Ultrascroll option scrolls new data very quickly but with reduced image quality. For most situations, the Fast setting provides a good balance. When using ClearVü or SideVü sonar views, the manual recommends the Auto setting so targets are drawn without distortion.

Using the Flasher View

The flasher shows sonar information on a circular depth scale, giving a real‑time snapshot of what is directly beneath the boat. The Garmin manual describes it as a ring that starts at the top and progresses clockwise. Depth is marked on the inner scale, and sonar returns flash on the ring at the depth where they are received. Different colors indicate the strength of the return. Because it shows what is beneath the boat right now rather than a scrolling history, it is the view to compare with a dedicated flasher. If the flasher page is not already on your home screen, you can add it through the Customize menu. For a deeper look at how flashers compare to traditional fish finders on the ice, see our ice fishing flasher vs fish finder guide.

Screen Elements and the Settings That Affect Them

The table below summarizes the main parts of a traditional sonar display, what they tell you, and which settings influence how they appear. All information is drawn from the Garmin STRIKER Plus manual.

A Note on Fishing Regulations

Fishing rules, including license requirements, legal gear, and size and bag limits, vary by state and by body of water. Before you head out, check the regulations on your state wildlife agency’s website. A fish finder helps you locate fish, but it does not change the responsibility to follow the law.

Frequently asked questions

Why do fish appear as arches on a fish finder?

The arch shape is created as a fish passes through the cone of the sonar beam. The Garmin manual explains that wider beam widths produce larger arches, and the scroll speed affects how the arch is drawn on the screen. When the boat is moving, the fish enters the cone, the distance to the transducer decreases, then increases, forming a curved return.

What is the flasher view used for?

The flasher shows real‑time sonar returns on a circular depth scale, with colors indicating signal strength. According to the Garmin manual, it is organized as a ring that starts at the top and progresses clockwise. It shows what is beneath the boat now rather than a scrolling history.

How do I reduce clutter on the screen?

Start by lowering the gain until the noise just disappears, as described in the Garmin manual. You can also enable the Surface Noise setting to hide returns near the surface, and use the TVG control to suppress clutter close to the transducer. The manual recommends using the lowest interference setting that still shows strong target returns.

For more help choosing and setting up a fish finder, browse our Fish Finders guide, which covers portable, castable, and mounted models, sonar types, and installation tips. If you are mounting a unit on a small craft, our kayak fish finder setup article walks through power and wiring considerations.

Sources

• Garmin STRIKER Plus Owner’s Manual

About Emmett Porter

Emmett covers beginner & family fishing, comparing specs, features and long-term owner feedback to help readers choose with confidence.