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Bass Crash Course: An Intro to Fishing Sonar

There's no denying that sonar in its many forms is an invaluable tool for all anglers. But in order for it to work for you, you first need to know how to use it.

One of the appeals fishing has always held for me is the attempt to solve a puzzle for which we don’t have all the pieces. Unlike hunting, where we’re looking directly at our quarry and the cover it inhabits, bass and other gamefish can seldom be seen as we look into the water from above. Fishing is a game of educated guesses as to where the fish "should be" and making casts to determine if our theory is valid.

While sonar has always been the primary means of getting a mental picture of what lies beneath the water, the technology has come a long way in the past few years. When I was learning to bass fish in the 1980s and ’90s, we had two technologies to determine depth and read the water column directly under the boat: flasher units (invented in the early 1960s) and two-dimensional sonar that printed the images out on scrolling paper.

Both technologies were effective for depth readouts but left much to user interpretation. The old paper graphs were predecessors of the 2D sonar we have today and could clearly define fish in the water column, yet distinguishing brush from vegetation or even large balls of baitfish could sometimes be a challenge with early 2D sonar.

Within the past 20 years, however, advancements in sonar technology have reached incredible heights with the introduction of down imaging, side imaging and, most recently, live forward-facing sonar. These sonar technologies provide such amazing clarity, resolution and detail that it’s like looking at a picture of the underwater world below. Not only is it easy to distinguish a brush pile from vegetation, we can literally count the limbs—and often the fish—within the brush pile.

With real-time, forward-facing sonar (FFS), anglers can now scan around the boat while fishing from the front deck to determine the presence of fish as they swim, note how they’re positioned around cover and even see how they react to the lure as it’s retrieved nearby. Anglers today have a near complete understanding of the previously hidden underwater world with this amazing technology.

Since there have been so many anglers joining the fishing community in recent years, this series is intended to provide a format to equip you with an understanding of how to implement the various sonar types. Perhaps you’ve recently acquired the technology and are wondering, “Now what?” In subsequent videos we’ll address questions such as: When should I use side imaging? Do I still need 2-D sonar if I have down imaging? And what’s a good strategy for using forward-facing sonar?

Certainly, everyone implements the various sonar types according to their personal preference. However, the information in future videos and articles is intended to equip you with the pros and cons of each of the sonar types and get you down the path of developing your own approach to sonar to catch more fish.

If you’re brand new to sonar technology, defining some terms will provide assistance moving forward.

  • Transducer: This device emits the sonar signal, or ping, into the water column and also receives that signal once it returns. Most modern bass and walleye boats have a transducer mounted to the exterior of the hull at the stern for imaging on the driver’s console and another transducer mounted to the trolling motor shaft to be used while fishing from the front deck. 2D, down-imaging and side-imaging sonar all emit from the same transducer; however, forward-facing sonar requires a separate transducer.
  • Control Head Unit: This consists of the display screen and “computer” that processes the signal from the transducer and displays it as an image on the display screen. Most bass and walleye boats will have at least one control head/display screen at the bow and one at the console.
  • Ethernet cable: A cable connecting two or more display screens that link the two units, allowing them to share data such as waypoints and sonar images. In order for multiple units to share information, they need to be from the same manufacturer.
  • Frequency: High-resolution sonar, such as down- and side-imaging, utilize a very high frequency sonar beam that produces images with picture-like quality. 2D sonar emits at a much lower frequency that is actually more powerful for imaging at extreme depths, which is typically not a factor in freshwater applications.

At the end of the day, sonar is simply a shortcut to fill in those missing puzzle pieces of what lies beneath the surface of the water. Sonar shows us where the fish are located and, just as importantly, where they’re not located. The result is more productive days catching fish.


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