How to Read a Fish Finder?

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Let’s face it – learning how to read a fishfinder looks pretty daunting, especially with the sheer amount of strange settings and features they have. For instance, what does side imaging mean? And why do you need a GPS? While these features can be very useful in the long run, it’s all for nothing if you don’t get over the initial hurdle of learning how to read them.

Fortunately, it’s a problem that can be easily remedied – and one that’s worth solving as well. Learning how to read a fishfinder can spell the difference between a good fishing trip and a bad one; with settings that can be especially handy for figuring out the best spot to cast your line and checking whether the conditions guarantee you a catch at all. So buckle up, my friend – let’s teach you how to read a fishfinder.

My problem with these kinds of tutorials is that they often spew out a ton of information with no sense of organization whatsoever, which is pretty counterproductive for a to-do article. That said, here’s a few things you’ll need to keep in mind while following this tutorial:

  • To understand how to read a fishfinder, you first need to understand how it works, so let’s get this out of the way before we proceed. Fishfinders make use of a sonar, or sound waves – when transmitted into the water, the wave hits an object and bounces back towards the device. Since they bounce back depending on how near or how large the object is, this helps the device create an image of what the object is.
  • The tutorial is divided according to the various features a fishfinder has, so it’s easier to digest and elaborate on each.
  • While fishfinders do share similar features, some may vary from brand to brand, so you’ll have to take note of these brand-specific features. For this, it’s best to consult your supplier on the differences in each.

#2, How to Read a Fishfinder

Like most gadgets, fishfinders have a default interface you get upon opening. Understanding this interface is the most important step in learning how to read a fishfinder. Usually, this is the sonar map, which is available for all fishfinder units. If you’re getting a sonar-only unit, however, you’ll probably get something that looks like this:

For fishfinder/GPS combo units, you have the option to display this alongside a GPS screen, so you can track your location while looking at what’s at the bottom:

For the sake of convenience, let’s dissect it screen by screen.

#Step 1: Understand the Sonar Map

This is a Lowrance 111HD, one of the older and more basic of Lowrance units. There are four things I want you to pay attention to: namely, the large 42.0, the smaller 41.0, the little arches, and the bottom graph.

  • The large 42.0 is your depth, which tells how deep the water is below your boat. Certain fish species thrive in certain depths, so if you’ve got a target species to catch, this could help you with your search. The depth finder is usually located at the upper left corner of your fishfinder.
  • The smaller 41.0 is your water temperature. Like the depth finder, this can also help you target a certain fish species, since some fishes (like bluefish) prefer warmer temperatures, as opposed to the more moderate temp-loving striped bass. You can usually find the water temperature underneath your depth finder.
  • The little blue arches you can find around the screen are your fish. Note that how they register on the finder can vary from brand to brand. Pay close attention to where they usually flock, since it’s another way to tell what kind of species they are. Bass, for instance, is said to be more active in structure areas, while halibut tend more towards flat areas.
  • Finally, the bottom graph is your fishing structure. This is especially helpful when you’re starting out in a new fishing area and are not familiar with the bottom structure. As mentioned earlier, certain fish flock towards certain areas, so it’s important to identify where and what those areas are.

Other fishfinders may include other metrics such as boat speed and time, but ultimately it’s how you use the combined information to score a catch. All good? Let’s get into the specifics.

Pro tips:

• If you want to know whether you’re on the rocky or sandy ground, all you need to do is see how dark the pigmentation on the sonar scan is. The darker the scan, the harder the surface

#Step 2: Understand the GPS

A mainstay of combo finders, the GPS screen is more important than you think, especially if you’re going out into the open water. Like most GPS functionalities with other devices, the GPS screen just maps where you are, which can help you keep track of fishing hotspots you’ve come across along the way, and track a course back in case you get lost. It can be especially helpful when you read it side-by-side with the sonar map, as such:

Aside from providing a map of your surroundings, other GPS screens (or chartplotters) can also display your coordinates as well, in case you’ll need to do some manual navigating yourself.

Pro tip:

• While you can zoom into your finder and close the plotter, it’s usually better to keep both on split screen to ensure that the two communicate effectively with each other for the duration of the fishing trip.

#Step 3: Understand the Types of Sonar

When learning how to read a fishfinder, you might have noticed that certain units display a different kind of sonar map. For instance, instead of the usual up-and-down grooves, you might see something like this:

That’s because the unit’s making use of side imaging, as opposed to the usual down imaging technology often utilized in fishfinders.

But what does this mean? Well, the terms “down” and “side” just refer to the direction your sonar takes. Some devices also offer both, although it comes at a price. That said, knowing what kind of sonar you’ll be needing is not just important to your fishing experience, but also to your budget. Let’s break that down a little further:

  • Down imaging is self-explanatory: the sonar scans what’s at the bottom of the boat, which results in a graph you read from left to right. This, of course, means they provide limited coverage, and are only good if you need to scan a specific part of your fishing area. However, because they focus more on one area, they also provide a more accurate and detailed picture of what’s beneath you. Being the more common kind of sonar, they’re also much cheaper than their other counterparts.

  • Side imaging, on the other hand, scans the sides of the boat, resulting in a graph that displays images from both the right and left sides. They’re also usually read from top to bottom, with the bottom part being what you’ve already passed by. When reading it, think of your boat as the blip in the center, with the two graphs representing what’s on the sides of your boat. Side imaging is especially useful if you want to cover a larger area, and are looking for accuracy in placement, like where on the side of your boat a certain school of fish is.

While it may be tempting to pit one sonar over the other, in the end, it’s really about what your goal is for fishing. In the meantime, perhaps the best option is to get a fish finder with both types to provide a clearer picture of where you’re fishing.

Video: How to Read Fish Finder Sonar Technologies

Video Credit: Wired2Fish

In conclusion

So that’s it for now Not so daunting now, is it? After all, when learning something new, I believe the more basic it’s made, the easier it is to learn. And, as you might have learned from this tutorial, learning how to read a fishfinder isn’t as hard as you think it is.

After all, with all the advances made to the tech, you’re sure to find more user-friendly iterations in the future. But while we’re still waiting on the ultimate fishfinder for keeps, just remember that a fishfinder’s worth the purchase if you ever come across one, with features that make it easier to conquer the seas and freshwater bodies. For now, however, the initial struggle will always be learning how to read a fishfinder – but at least it’s one that’s easily overcome.

I am an avid outdoorsman with experience in naturalist education, outside adventure education, ski instruction, and writing. In addition to my outdoor hobbies, I started this blog to provide advanced material, guiding you towards a better and more comfortable outdoor experience. I enjoy sharing my experiences of backcountry education teaching and guiding through writing. To contact Davis, visit the contact page. and About Us.