Fish finders are one of the most important add-ons for fishing kayaks or boats. Some might argue here but consider the guidance it provides to an angler new to this sport, It is just as much useful to a veteran even after years.
But how does one read the pictures on a fish finder screen properly?
When you look at the screen for the first time, it looks like a messed-up artwork, right?
Well, it is easy to guess where the seabed is. But where are the fishes? Fishes move a lot, right? But there’s no moving fish in it. Why is it generating all those arches? I mean, come on!
A fish finder screen is considerably confusing and often misleading. It’s understandable. But honestly, it is so until you get the hang of it.
After that point, it is like reading through a newspaper. Where are the similarities? Well, both are kind of tricky to find the information at first, But hella useful afterward.
I hope you understand the basics or rather the working mechanism of a fish finder. It uses sonar to identify submerged objects and displays the information on the display.
It is also called echolocation. The transducer handles the analog part of the process, while the processor handles the electrical signals sent from the transducer as well as calculations. I hope you have basic knowledge about transducer.
In short, the fish finder creates short beats or pulses of ultrasonic sounds. The sound travels through the water until it is intercepted by something. Once the sound pulses hit an object, the object generates an echo of the sound.
The echo then travels back and is picked up by the transducer. The transducer converts the receiving sound pulses back into electrical pulses for the fish finder to read, calculate, and display.
Now, different objects make echoes of different strengths. Another main factor in understanding is that the bigger an object is, the more echo it’ll make. But it’s common sense, I guess.
Now, that’s the summary of how a fish finder works. It is important to understand the basis to understand the seemingly random markings on the screen. That’s because it is not random. I’ll explain how it works.
How Do You Read Pictures On Fish Finder?
Yes, that’s right. A fish finder’s display shows pictures or rather a picture. More on it later. Now, we know how the sonar works, right?
After the transducer picks up a volley of echo and sends the signal to the main fish finder, the processor squashes the 3D readings of the subnautica into a very brief 2D representation.
Think of it as a long thin bar. The whole picture is made of a lot of such bars. Each time the fish finder creates a new bar, it shoves it on the screen on the right end. The one on the very left gets removed.
So, with each tick of the transducer, the main part of the picture is shifted toward the left, but the very left part is removed, and newer information is added on the right.
You can think of it as a mini diary because it keeps the information for a short while until it gets pushed out. Once an information bar is registered, it will never change or update.
What Are The Signs On The Screen?
When you take a look at the screen, you can see a few types of signs. They represent different objects.
- The Seabed
I guess this is the most obvious object to identify. The continuous curvy line at the bottom of all the excitements is the seabed. There’s usually nothing beneath it (there’s one exception, more about that later).
If suddenly the seabed plummets, and goes out of the screen, that usually means the ocean is too deep for the fish finder to scan the bottom.
- The Arches
They are also another kind of obvious mark, hard to miss. These marks are usually what you are after. What are those? You guessed it, fishes. When a fish enters the scanning zone of your fish finder, it starts creating an echo. It continues to do so, as long as it is inside the scanning zone until it leaves again.
For the nature of how a fish finder works, when a fish swims in a straight line through the scanning field, this creates an arch on the screen.
A common misconception is to mistake the size of the fish being proportional to the length of the arch. It is not the case, though.
The length of the arch actually shows the time the fish has spent in the scanning zone. Remember, the fish finder adds a bar of information on the screen with each tick of the transducer.
So, if the fish swims along with the boat, the fish finder will keep adding its presence on the screen, effectively making a long arch/line.
However, the size of the fish can be guessed from the thickness of the arch. I previously mentioned that a bigger object would generate more echo, right?
That’s common sense.
And the way a fish finder works is it represents the amount of echo received, or rather the potential size of the object, by the thickness of the display object.
- The Half-Arches
If you’ve spent some considerable time with a fish finder, chances are you’ve encountered them a handful of times. They are not all that distinguishable or different from full aches either.
They simply just carry one extra piece of information. When a fish enters the scanning zone and leaves without passing the whole diameter, that creates a half-arch
All the other rules of deducting the fish size and nature are the same as a full arch. Honestly, they are not always all that obvious to see either, But I thought, I’ll mention it, just in case someone has a question regarding it.
- The Lines
From time to time, you can come across straight lines on the display. They can mean quite a range of things. The most common occurrence is underwater plants of other kinds of vegetation.
They are stationary objects, and when the boat slowly surfs above them, they show up as a straight line. Trees/similar objects can make both horizontal and tilted lines.
Another reason for their appearance is actually fish swimming parallel to the boat’s motion. They are thus staying in the scanning zone for a prolonged period.
- Fish Icons
Now, these types of marks are exclusive to some specific models of fish finders. Some advanced fish finders can automatically distinguish between different types of echoes. They are programmed to display various icons on top of the arch, genuinely fish.
- The Second Layer Of Ground
Sometimes, at some locations, you can spot the second layer of ground mark underneath the obvious seabed. Those are not actually a second layer of ground. They don’t even exist actually.
For the most part, it happens because the seabed consists of very strong materials, which reflected a big part of the sent sound pulse. It was picked up by the transducer, and thus the seabed image is created.
However, the echo was strong enough to travel to the surface and reflect again from the surface. It then reflected a third time from the seabed and finally made its way to the transducer. When the transducer picks them up, the fish finder shows it as a different layer under the ground layer.
What Are The ‘Not-So-Dense’ Clamps?
From time to time, you might come across some clamp or cluster of dots, or smaller lines, or probably simply just a misty or cloudy patch.
Much like other objects, these cannot be sure about either, because you can’t see. However, there is a good chance; they are baitfish. Baitfish hang around in groups, and the groups are usually jam-packed.
To a fish finder, they seem like a mess. Anyway. They can be some other objects as well, like underwater shrubs, debris, wrecks, or whatever. You’ll get a better idea over time.
To Sum Things Up
There are many models of fish finder out there; some are naturally more advanced than others. And not all the fish finders work on the same frequency. Thus, the output of your fish finder might not exactly match mine.
But except for some minor mismatch, the majority of the fish finders work in the same way. In this article, I tried to cover the most common and most frequently occurring marks.
In other words, rather than specializing on a specific model of a fish finder, I generalized it instead.
Overall, you need to be familiar with your device; there is no alternative to that. Only then can you properly understand what’s going on down there. I just tried to give you a head start. I hope you have a great fishing experience!