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How to Use a Fish Finder Effectively

Technology has begun to permeate every aspect of modern life and understanding how to make the best use of the tech available to you can be a huge performance booster. I remember the first fish finder we put on the old red family boat – I think there were about 20 pixels on the entire screen. Today’s fish finders often can be paired with GPS and many units are combined. Units may have onboard memory, color screens, and dozens of cool new features.

Let’s take a look at how to use a fish finder effectively.

Using a Traditional Fish Finder

If you go and pick up a budget minded fish finder, you’ll most likely end up with a classic transducer based fish finder. These fish finders operate at a low frequency (remember fish finders us sonar) and display a brief picture of the sub-surface world under the water.

When using these fish finders, the unit sends out a blast of sonar every so often and then records the data which comes back. As this data is collected the screen populates from right to left and gives you a “picture” of the bottom.

Anything which causes sound waves to bounce back between the boat and the bottom is, ideally, a fish!

These fish finders can be difficult to use when moving slowly or stationary. They’re best used when moving steadily and to get an understanding of depth, features, and bottom type. The thicker the bottom line appears on this fish finder, the softer the bottom. A thin bright line representing the bottom most likely indicates a hard surface such as rock.

One trick to using these fish finders effectively is to remember that the chart always moves right to left. This isn’t based on your movement, it’s based on a time scale and when you’re anchored or not moving, the chart will continue to scan the same area and still move across the screen left to right. Just remember, this means the sonar is scanning over the same location time and time again. This can cause confusion or difficulty in understanding what is being displayed on screen.

Using a Side Imaging Fish Finder

Side image fish finders are a little less intuitive at first but once you learn to read them you’ll see that they often represent an eerily accurate “snapshot” of the underwater world below you.

Side Image and down image fish finders use a higher frequency sonar pulse to read the objects below water’s surface. This causes massive improvements in clarity but comes with one drawback:

These higher frequency sonars lose effectiveness if you’re reading depths more than 100-200 feet so they may not be appropriate for deep water fishing.

Learning to read these images is pretty intuitive – often what you see on screen looks exactly like an image of the objects under the surface. You can see submerged trees, objects, and fish in surprising clarity! Potentially a great solution for fishermen spending most of their time in shallower waters.

Like the traditional fish finders, these sonar devices continually emit sound waves and interpret the signals received. When anchored or not moving, it’s important to remember you may be seeing the same scan over and over again.

Adding a GPS

Marine GPS units are widely available and some anglers may advocate purchasing a GPS and fish finder separately but we’re pretty sure you’ll enjoy the improved functionality and use of a combo unit.

Often called chart plotter – fish finder combination units, these little devices use an on-boat GPS and sonar setup to record and display both location and underwater characteristics.

Why use both? Because the combination allows you to track locations of great catches, and notable sub-surface structures you may want to revisit. On top of that, it’s sometimes helpful to be able to find your way home when you’re far offshore and need to return to harbor. Just set a course on the GPS and off you go.

We recommend the combination chart plotter and sonar units for advanced fishermen; especially those participating in deep water fishing and offshore fishing where it may be difficult or impossible to track location or judge depth when out of sight of land.

Fish Finder Reading Tips

Practice using your fish finder to seek schools of fish and note their depth. As you work the lake or water, try a few casts when you think you’ve found an active school of fish and note results for future reference.

Avoid schools of fish that seem to be huddled up or tightly hugging the bottom. These fish are often inactive and unproductive to try catching; it can be hard to convince these fish to bite for you.

If you’ve been able to find activity at a certain depth, continue to make note of this and what type of fish you’re finding at that depth. If you’re finding the fish you want, then look for other areas with plenty of coverage at the depth you’ve been having luck with. Similar fish tend to occupy the same type of territory in a body of water so keep looking for more great spots!

Don’t get too wrapped up in reading every little blip on the graph – false positives happen all too often and you may want to take the images you’re seeing with a grain of salt.


With technology evolving most fishermen can afford a side image or down image sonar – we recommend it for the superior viewing performance.

Learn to read structures and schools of fish as you practice with the fish finders and remember that actually getting the lure in the water is the only way to catch a fish. Don’t get stuck in front of the screen too much!

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