At first glance, using a fishfinder may seem complicated, but once you understand the technology behind the machine and some basic functions, you will quickly become a pro at finding fish.
However, before we delve into the world of sonar, transducers and LCD screen resolution, let’s talk about fish finding without marine electronics. Even if you have a fishfinder, you still should try to develop your skills at discovering fish with your eyes, ears, and local knowledge.
Look and listen for breaking water, splashes and swirls to locate fish. Fish hang out around structure, so find the rock piles, ledges, weed beds, and shipwrecks in your area. And you can do that without a fishfinder. Ask around or buy a fishing chart. Getting yourself in the ballpark when looking for fish will make using a fishfinder easier and much more productive.
Fishfinders, also called sounders, bottom machines, and sonar can help even the most experienced anglers learn more about what is below your boat. Fishfinders utilize sonar technology, which stands for Sound Navigation And Ranging. It was developed in the early 1900s to detect submarines.
In simple terms, sonar works like this: Sound waves are sent from a transducer toward the bottom of the body of water your boat is traversing. When the pulse hits something solid, like the bottom, rocks or a fish, an echo is transmitted back to the transducer.
The fishfinder’s internal computer processor measures the time it takes the pulse to return from the object to the transducer. The time difference between the sent and received signal allows it to calculate with great accuracy the vertical location of the object. With tons of collected information cobbled together, the fishfinder draws a picture on the display.
Mount the Transducer Correctly
The transducer must be mounted correctly. Read the manufacturer’s installation manual and follow the directions carefully, or hire a professional to do the job. There are three main types: transom, thru-hull, and shoot-through. They can also be mounted to trolling motors.
Frequency and Depth
One of the key specifications for a fishfinder is its frequency. They are sold in many different frequencies, including 38 kHz, 50 kHz, 120 kHz, 192 kHz 200 kHz and even as high as 455 kHz. Remember this: The high frequencies, say 192 kHz and above are effective for fishing in depths of 400 feet and shallower, while lower frequencies are better suited for deep sounding.
The sounds waves are transmitted in the shape of a cone, like a flashlight beam. Lower frequencies transmit narrower cones, which are more effective in collecting data in deep water. Higher frequencies produce wider cones that are better in shallower water. Many machines can be operated in two or even three different frequencies. So look for a fishfinder with a frequency that suits the depths of your fishing area or a multi-frequency unit that can be tuned as needed.
Color or Monochrome?
Today’s fishfinders offer good value and for most anglers, a monochrome display should do the job. Prices have dropped, and most are now sunlight viewable with TFT technology. So why not get a color version? They cost more, and in some cases a lot more than monochrome units, which can be found for under $100.
You should be familiar with screen resolution, which is the horizontal and vertical pixel count, such as 480 x 272. The higher the resolution, the better the picture and since with a sounder you are looking vertically into the water column more pixels on the vertical axis of the screen is good.
Other useful features include zoom or bottom lock or shift, all of which let you hone in on a particular area of the water column. Expanding the view of a portion of the water column onscreen will let you see more detail and help distinguish fish from bottom.
Beginners Should Stick with Auto First
If you are a rank beginner at using a fishfinder, keep the unit set to automatic for now. You should use the auto depth and auto gain functions until you become familiar with the machine. Doing so will get you a decent image on most machines and should keep you aware of the water depth in nearly all conditions.
While in the auto modes try out your fishfinder marker mode or depth cursor capabilities. This is a good way to start using the machine without taking it out of automatic modes. On most fishfinders the depth marker will be turned on with the push of a button and moved up or down with arrow keys.
When you are ready to move to your first manual mode, you can use the depth cursor to find out exactly at what depth an object, let’s hope it is a big fish, is located. Just move the cursor over the object to get that depth reading.
Using a Fishfinder—Manual Gain for Max Performance
Probably the most important function and setting you will need to know when using a fishfinder is how to control and use manual gain, on some machines this will be called sensitivity. This is such an important function that many fishfinders have more than one automatic setting for gain. To be really precise when using manual gain you will need to fine tune the setting whenever your depth changes more then about 10 feet.
There are two ways to set the maximum gain manually. The first method requires you set the depth manually to at least twice the water depth and then turn the gain up until you begin to see s second bottom echo at roughly double the real depth. You should look carefully at the screen so you get a mental picture of how much noise is being displayed onscreen.
The second method requires a little more experience, this time you will simply manually dial up the gain until the noise level onscreen matches what you memorized from using the first method a number of times.