Informational Guide

How To Use A Fish Finder

Find out everything you need to know about how to use a fish finder. No matter the brand, our guide will help you understand how to use your fish finder.

by Andrew

Informational Guide

How To Use A Fish Finder

Find out everything you need to know about how to use a fish finder. No matter the brand, our guide will help you understand how to use your fish finder.

by Andrew

by Andrew

Fishfinders use a sonar sensor called a transducer to chart the water column features like vegetation, structure, and fish. There are several important functions of a fish finder, but if you read through this comprehensive guide, you'll know enough to pick one of the best from this link and put it to good use out on the water.

  • Locate Bait
    Although they may appear as thin or incomplete arcs, both schooled and individual baitfish will appear on display.
  • Identify Fish
    Some fish finders use fish icons to indicate a fish's presence, while other, more sophisticated models show the size and movement of fish in what’s referred to as a fish arc.
  • Navigate
    More advanced fish finders may also be equipped with GPS and, in that case, not only help find fish but also help anglers reach fishing spots and return to shore without issue.
  • Safety
    Anglers can avoid underwater hazards with fish finder readouts.

Understanding a Fish Finder’s Main Features

Zooming Feature

Allows the user to focus on a specific range in the water column. Useful for trolling anglers who only need to see the bottom or anglers fishing in cold environments. Zooming in also gives greater target separation between fish and other elements like vegetation.

Tuning Sensitivity

Increasing sensitivity allows the fish finder to pick up on smaller things while turning it down can reduce clutter. Reducing the sensitivity will make smaller baitfish and insignificant things disappear so you can concentrate on larger targets.

Speedometer Tool

Many fish finders measure the speed of the boat, but some require extra equipment to do so. GPS-fishfinder combos are more accurate than paddle-wheel attachments. Some anglers also prefer to buy smaller fish finders that can measure speed at a fraction of the cost.

Water Depth Sensor

Measuring depth is handy for seeking out individual species of fish if you, say, know that catfish are most commonly found between 35 and 70 feet of water. It’s also essential to make sure you don’t run your boat aground or onto a sandbar.

Fish ID Technology

Companies like Humminbird have developed technologies that allow the device to compare information found in returning signals to a database of fish species’ characteristics. The fish finder then identifies the fish with either an icon or a label, as well as a depth read on the fish.


The overlay of a GPS receiver on a map is called a chart plotter. Fishfinders with this feature allow the angler to keep an eye on their current location. This can help reach a certain spot or record a traveled path to learn more about a given location.

How to Use a Fish Finder

1. Read the Manual First

Manuals usually have a wealth of information, including operation and installation instructions, locations for software updates, and an outline of the power requirements. You’ll be much more comfortable using your fish finder with this basic knowledge of it.

2. Understanding Fish Finder Screen Display

It takes a little time to learn what the different elements on a fish finder display mean. Find where basic aspects like speed, depth, and temperature are and then move on to the shapes of fish arcs and vegetation. Learn what your fish finder screen is telling you to get the most use out of it.

3. Identify Fish, Judge Fish Size

Fish icons and labels help identify fish, but so is the size of the fish. The width of a fish arc will tell you how big the fish is, with thicker lines representing larger targets. It can also help locate bait. Adjusting sensitivity is a good way to reduce clutter and concentrate on only the larger fish.

4. How to Identify Different Types of Underwater Structure/Terrain

Drop-offs can be challenging to spot on a fish finder unless you know what to look for, but dips are generally much easier. A fish finder with side imaging will give a much clearer indication of what exactly is on the bottom, which is great for picking out sunken logs and other cover.

5. Locating Fish & Mapping the Area

Sweeping an area with a wide beam is a great way to locate fish and allows the angler to mark possible hazards and appealing fishing spots. Waypoints are the best way to create your own personal map of a body of water. 

6. Using the Chartplotter & Marking Waypoints

Waypoints are like pins on a map representing the device’s current location. Mark places where fish are schooled or note cover with waypoints and guide your boat back to that spot using the GPS in the chart plotter function.

7. How to Adjust the Display

Some fish finders can organize the different display modes in tiles, allowing you to see, for example, traditional sonar, side-view, and down-view simultaneously. It’s also possible to adjust contrast and brightness on the display for fishing in bright sunlight.

8. Peaking the Transducer

To get the strongest signal out of a transducer, you can peak it by setting the depth range to two or three times the depth of your location. Work the sensitivity up from 10% until a second echo, represented by a second line beneath the actual bottom, appears clearly.

People Also Ask (FAQs)

What do fish look like on a depth finder?

Fish can appear as icons if the fish finder has fish ID technology, or they can appear as fish arcs, which are a series of points that indicate their size, location, and movements. Understanding how to interpret the thickness, shape, and completeness of a fish arc allows the angler to get the most information possible from fish finder readings.

How do I use a fish finder for ice fishing?

Ice fishing fish finders are specifically built to endure the colder conditions and the more vertical aspect of ice fishing. If you’re using a flasher, the water column is represented by the circle and a few colors. Essentially, you drop the transducer into a hole in the ice and let it hang there to see the whole water column beneath you.

How do I use a Vexilar fish finder?

Vexilar fish finders are generally built for use while ice fishing. They have also created some transducers that are specially made for use on the ice. They typically work more similarly to a flasher unit than a standard fish finder.

How do I use a Marcum fishfinder?

Marcum fish finders also resemble flasher units, and they’re not suited well for really shallow water. Most are simple to operate, having only a knob to adjust gain and another to adjust depth range. Many also have a zoom function to take a better look at a certain zone of the water column.

How do I use a Humminbird fishfinder?

Humminbird makes some of the most sophisticated fish finders on the market, typically offering GPS, chart plotting, side-view, down-view, and traditional sonar. Take the time to adjust the screen organization and the settings before you start using a Humminbird to make sure it works as effectively as possible.

What is a fish finder rig and how do I use one?

A fish finder rig is a type of bait rig used in saltwater fishing to catch species like tarpon or redfish. Tie a pyramid sinker onto the mainline with a snap swivel and attach a leader with a ball bearing swivel. Cast this rig far out into the waves and let it hit bottom; it’ll bounce and won’t wash away in the waves.


Fish finders are some of the most useful tools in an angler's arsenal, provided the angler knows how to use them. The trick to effectively using a fish finder is to familiarize yourself with the device, organize the screen and settings to suit the situation, and learn how to read all the information the transducer returns.