Fish finders are elegantly designed. They use the principles of sonar in order to understand what’s going on below the water, then translate the signals they receive into a display to turn the data into something you can understand.
How does a fish finder know that it’s a fish? It doesn’t. It doesn’t even know that it’s a fish finder. It’s not sentient!
Jokes aside, your fish finder won’t necessarily know that what it’s displaying is a fish - though some fish finders do have that ability (to a certain extent). Instead, it will simply display an arch - and you, as a seasoned user, will know that the arch is a fish.
But why are fishes displayed as arches? How does fish-finding technology work? And can your fish finder tell that an arch is a fish sometimes? We’re going to answer all these questions and more. Let’s dive in.
The principles of sonar are fairly straightforward. Your transducer will emit sound waves and measure how much time it takes for those soundwaves to return to the transducer. By measuring this echo, your sonar can tell how far an object is from the transducer, the shape of the object, and which direction it’s moving in.
Fish are displayed as arches on sonar because they are moving objects. When the fish enters the cone, it creates the bottom left portion of the arch. As it moves toward the center, the top of the arch is created, then the bottom right portion. This is a consequence of how sonar is displayed - it’s a graph that shows readings over time. In other words, the arch isn’t the size of the fish - it’s its location over time.
The thickness of the arch, on the other hand, will tell you how large a fish is - the thicker the arch, the bigger the fish. That’s because thicker objects give stronger readings.
Some fish finders have fish alarms. By and large, these alarms are quite simple: They’ll tell you when they detect an object that’s suspended in water and passing through the cone of your transducer. That means these alarms may trigger when non-fish objects suspended in water pass through the cone - but for the most part, objects suspended in water are fish. You can often set these alarms to only trigger when large objects pass through the cone.
FIsh finders may also have a feature that allows you to automatically change arches to fish icons. This is done using an algorithm that detects which arches are most likely to be fish. These modes will often feature a display, which tells you how deep the fish are. They will also use larger fish icons for large fish!
Most experienced users don’t use fish icons - they learn to read the arches. You’ll learn how to interpret fish finder displays better than current algorithms can by studying the fish that you’re trying to catch. Understanding their behavior and learning to read arches to understand how quickly fish are moving and how big they are - those things can only come with experience.
Start using a fish finder now - like anything, practice makes perfect. We’ve done reviews on all of the best fish finders on the market - take a look, and you’ll find one that’s right for your needs.
See you on the water!
