Understanding SONAR
SONAR technology – which fish finders use to help you catch fish – can really bring your fishing to a whole new level. Many of the world’s top anglers preach that 90% of the fish are in 10% of the water. To have more successful fishing trips, you just need to put yourself in that 10% of water.
SONAR technology has made leaps and bounds when it comes to fish finders – with Humminbird and Lowrance coming out with so many innovations like Down Imaging, Side Imaging and StructureScan, high-end fish finders are almost as good as having a camera underwater or taking a dive for yourself!
Still, professional anglers still seem to prefer traditional 50, 83, or 200 kHz SONAR alongside side and down scanning SONAR – so what is so special about it?
Fish Finders
Note – Understanding everything about your fish finder is a topic worth an entire book. The focus of this article is spotting fish, which, after all, is why we use fish finders to start with! You can check out these articles for more details on how they work and how to choose the best one.
What to see on your screen
Before we get to that, a quick recap on how traditional SONAR works – the image starts from the right side of your screen – so an echo you see on the very right of your screen is what is directly beneath your boat. As it moves further to the left, that’s how far behind it is.
You can get an idea of this on your boat with your particular fish finder by getting a feel of how fast your boat is moving and the quirks of your individual unit.
Echo colors determine hardness
The greatest advantage you gain from traditional SONAR is that you develop a deep(pun intended) understanding of where you are fishing. Couple that with the fact that most of us have a favorite lake or two that we usually go to, and you can really become the master of the water!
While you can apply this technique to a grayscale fish finder too, a color screen will show you even more detail. The echo’s strength determines the color – basically, the harder the object, the stronger the echo.
It’s just like bouncing a ball on the ground. On a beach, the ball won’t bounce much. On grass, it will bounce a little more, and on concrete, it will bounce the highest.
Applying this to echoes, on normal settings, a weak echo will be yellow, something slightly stronger will be green, even stronger will be orange, and the strongest will be red.
Note- your individual fish finder’s settings may be different. To clarify: • Strong echoes will give STRONG, solid colors
• Medium echoes will give MEDIUM colors
• Weak echoes will give wispy, weak colors
If you are using a black and white screen, you will need to be a bit more discerning – weaker echoes will be lighter, and stronger echoes will be darker.
Seeing the bottom
Perhaps the most important things you will look at on your fish finder are the depth readings(in feet or meters, depending on the settings), and the bottom!
Bass generally prefer firm bottoms rather than muddy or silty bottoms, so you are looking for a strong red(or any color as long as it’s very solid) line for the bottom.
You will obviously see a lot more than just the water column and the bottom, so here is a quick-and-dirty way to determine what’s what: • If it’s attached to the bottom, it’s likely a rock, a tree, brushpiles, or sunken objects
• If it isn’t attached to the bottom, it could very well be a fish!
How fish arches appear
“Fish arches” are probably the most famous fish finder-related term there is out there! Almost anyone who is new to fish finders and has researched them to some extent would have come across the term “fish arch” sometime or the other.
So do fish only appear as arches? Not quite! Fish arches form when a fish swims through and through your transducer’s SONAR cone.
To understand this, imagine an upside-down cone coming out of wherever your transducer is. This “cone” is what your transducer is actually seeing. Generally, a lower frequency will have a larger cone. When a fish swims into the cone from one side and out of the other, you see an arch.
This is because the fish entering the arch will give a weak echo(showing up as a slight curve). As it reaches the middle of the cone, it will give the strongest echo(showing up as the meaty center of the arch), and as it exits the cone, it will give a reading similar to the first one, forming an “arch.”
But what happens when a fish is just hanging out inside the transducer cone?
How to spot fish
This is when it gets interesting. If a fish is just hanging around inside the cone, it will show up as a straight horizontal line! Sometimes we may write this off as disturbance, but it could very well be fish!
Another great way to spot fish(gamefish, specifically) is to look for large, wispy blobs of echoes that are not attached to the bottom. These usually indicate schools of baitfish. And where there are baitfish, there are gamefish!
If you look closely, you may even be able to see a slightly stronger and larger echo among the wisps – those are usually gamefish(bass!) that are lurking around waiting for their next meal!
Making the perfect cast
Now that you know where the fish are, you can cast your line exactly where the wisps are. Cast your line, and watch it sink down to the bottom – it will be a thin but noticeable line going towards the bottom at an angle.
Once you see on your screen that it has reached the middle of the wisps, you can play with the bait a little bit, bouncing it up and down to get the attention of your target bass. You can see the line moving up and down on your screen, too, as a zigzagging line.
Then you just have to wait and see! For an even more visual idea of this technique, you can watch this excellent video by Humminbird Australia.
Observe to learn
On a closing note, the best thing that you can do with your fish finder is learning to spot patterns. Many pros such as Don Allphin can even tell what species they are looking at just by seeing an echo. It’s not that they have super-human eyesight or a futuristic fish finder – they have just learned to see what kind of fish is found where!
When you see something interesting, cast your line and see what you get! After enough trial and error, you too will get a feel for what you are seeing on screen. Plus, you have more excuses to take your boat out on the lake!
By Shabbir Nooruddin. Shabbir is a fish finder enthusiast and is the founder of Fish Finder Source – and they are proud to be the #1 place for fish finders on the web! Click Here to visit.
