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Fishfinder Settings and Use For Catfishing



I have covered extensively choosing a fishfinder for catfish and some of the basic features to look for, including the differences between traditional broadband sonar, down imaging and side imaging and covered my 2011 top fishfinder choices for catfishing as well as how I use GPS for catfishing in recent weeks here at Learn To Catch Catfish.

I can always tell when I have hit a subject that people really want to know more about because it often sets off a firestorm of questions through the ask a question page and using a sonar fishfinder for catfishing was certainly one of those topics.

A sonar fish finder is the blue catfish anglers #1 tool but it is without a doubt not a magic bullet. It is not going to catch fish for you, but it is one of the most important tools in an arsenal of tools that will help you successfully locate and catch blue catfish on a day in and day out basis. Sure, people fished for ages without the use of this high tech equipment and caught plenty of fish but using sonar in the quest to find fish has certainly changed the game and made anglers much more effective.

I rely on my sonar as one of the tools for finding and catching blue catfish almost 100% of the time.

It would be impossible for me to cover everything you need to know about finding fish and reading a fishfinder in an article or two so I want to address some of the basics of using a fishfinder, answer some of the more common questions I have received and hit some of the highlights to help you get started. Ultimately I am going to put together some more materials to help everyone learn but that’s a long term project I am working on.

As I mentioned in my article on my top picks for 2011, I am using some older technology (a Lowrance LCX15MT) but am in the process of upgrading to a Lowrance HDS series unit and having some of the capabilities available in that newer unit will make the materials a lot easier to put together (as well as more relevent).

Here are are some of the basics and common questions I have been receiving:


Basics Of Using A Fishfinder For Catfishing

Before I get into the common questions I want to address installation. If your new to this or are replacing your sonar make sure you have a good clean installation and the transducer is mounted in the right place. If this is not done correctly you will never get a good picture on the screen. One of the most common issues I see is transducers mounted too closely to the motor, rendering a poor or unusable image. How close should it be? It varies from boat to boat, if your not sure, find someone who knows before you start drilling holes.


What are the basic settings that I should use for my fishfinder?

It is going to vary slightly from unit to unit and will be dependent on the features that you have. I asked around and it appears that most of the readers are using black and white broadband sonar and these settings will be relatively consistent for all black and white broadband units, these are the exact settings I use on my Lowrance LCX15MT and my Lowrance X135.

1. Fish symbols – Some units will refer to this as “fish id”. These are the stupid little pictures of fish that show up on your screen. You want these TURNED OFF in all instances. These are of absolutely no use and provide no value at all.

2. Chart Speed – Set this to 100% (This controls how fast the picture moves across the screen, lowering this to less than 100% slows the picture down)

3. Ping Speed – Set this to 100% (This is the amount of times per second the transducer sends a signal, more pings = more signals per second = more data)

4. Sensitivity – Set this to approximately 78% to 80% in deeper water (greater than 25 feet). It can help to adjust this in shallower water (less than 25 feet) and reduce to 60% or 70% but I usually don’t mess with this and never have an issues as a result.

5. Auto Sensitivity – Off – This automatically adjusts the sensitivity. Learn to adjust the unit manually to maintain a clear picture and you will have better results. As stated above once you get “dialed in” sensitivity should require little adjustment.

6. Gray Line – Set around 55% based on settings above. This helps determine the bottom composition. A soft or muddy bottom will return with no black line or a very thin black line. The harder the surface the signal is hitting the thicker that black line will be across the bottom.

7. Dept Range – There will be something that says auto depth range. Use this setting or make sure it is set so you always see the bottom in full screen.

8. Surface Clutter – Set at 0% – All this does is reduce the noise that reads on the bottom of the lake. Since traditionally most of the time you will be focusing on the bottom part of the water column just set this to zero. You shouldn’t have to mess with this unless you are for some reason concerned with what is in the upper third of the water column.

9. Unit Of Measure – Set to feet/Fahrenheit- Pretty self explanatory.


I have a lot of pictures of little fish on my sonar fishfinder, how do I tell which ones are catfish?

Refer to my comment above on fish symbols or fish id functions. You want these turned off at all times and it is the very first thing you should do. These “little fish pictures” on your screen provide absolutely no value at all.

To get a better understanding of this turn the fish symbols off and on and you will get a better idea of the effects.


How do I get arches to show up on my sonar unit and what do arches mean?

Use the settings outlined above.

As your boat passes over a fish a display pixel registers on the screen. As your boat moves over the fish the distance to the fish decreases so the arch gets higher and thicker. As you continue to pass over a fish the distance again begins to decrease creating the other side of the arch. The center of the arch is created when the center of the transducer cone is directly over the catfish.

if the catfish does not pass directly through the center of the cone the arch won’t be as well defined. This is because the fish is not in the cone of the transducer very long so there aren’t as many echoes to display on the screen.

There has to be movement between the boat (idling with the main motor or moving slowly with the trolling motor) and the fish to develop an arch or create a more defined arch. If you are anchored or stopped arches will be less noticeable.


You mentioned that you use your sonar fishfinder constantly for blue catfish, do you use it for channel catfish also?

Yes and no. The very first thing I look at when fishing is water temperature and I monitor water temperature at all times. Water temperature can vary greatly in different depths and in different parts of the lake and this has dramatic effects on all species of catfish. I do a LOT of shallow water fishing with slip bobber catfish rigs for channel catfish so I rely on my gut more than I do anything to find channels but my sonar does come into play when I fish in deeper water for channels.


I bought a used Lowrance X135 on eBay after reading your article and it did not have a transducer. I went to buy one and the guy asked me if I wanted a 20 or 8 degree cone. Which one should I get?

You want a wide cone which is a 20 degree cone. This relates to the width of the echo sent out from the transducer. For freshwater you always want a wide cone. The difference between a wide and narrow cone is very significant and gives you a much smaller view of what is happening below the boat in depths you will encounter in freshwater.


When I am driving across the lake at high speeds I cannot see a picture on my screen, how do I fix this?

Your not supposed to see a picture when driving across the lake at high speeds and if you did, what would you do?

When your driving across the water at high speeds in your boat it creates cavitation. Basically what that means is there is a lot of air bubbles kicking up around the back end of your boat from the motor and coming from under the boat. The transducer is made to work in water, not air and these air bubbles make it difficult for the screen to render a clear picture or a picture at all.

This is common and honestly if your running across the lake at that rate of speed are you going to stop because you see a fish and if you do are you going to be able to get back to that exact location where the fish was?

Get to the area you want to look and then idle down and drive slow and look. You will get the best results from your electronics and produce more results when you get your baits in the water.


I have heard that on color units you can tell the difference between catfish and other fish by the color of the arch. Is this true? Also how do you tell the difference between catfish and other fish on a black and white unit?

Yes it is true that on color sonar you will get arches of different color for catfish and scale fish. This depends a lot on the settings but when “tweaked” and set correctly catfish will show yellow and red arches and most scale fish will return blue and greenish arches.

One a color graph it boils down to experience and having a trained eye. You have to use where the fish are in the water column and the size and shape of the arches.


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About Chad

Chad Ferguson is a professional catfish guide and founder of Learn To Catch Catfish. Click here to subscribe for more exclusive catfish fishing tips by email and then follow on Twitter or Google


  1. Aaron aka Odwraca says:

    For us bank fisherman, have you seen the ones that you can use from the bank that run about $80? Are they worth using for guy stuck on the bank?

    • I have not personally used them but have discussed them with a few people. The general feedback I have heard was they are a waste of money.

  2. Bob Mueller says:

    Chad has hit the nail on the head. You always are able to cut the fluff and tell how things work best and help us to catch more catfish. This is a great post and should go out to people who just do not know what to do with the great technology we have available. Thanks for shooting straight.


  3. Chad,
    I always look forward to receiving your articles and read them with anticipation of catching more fish. Was very interested in the questions and answers on using sonar. I’m trying to learn to adjust and read the sonar correctly in order to put me on the fish. I had always wondered about the fish ID on the sonar and was glad you responded to that. Thanks again and hope to meet and fish with you sometime. Just returned from a guided trip in Branson, Missouri where we slew the trout. Thanks again.

  4. butterbean carpenter says:

    Howdy Chad,
    Thank you, for a very informative article… I’m sure there are lots of fisherpersons who will get an education from this piece..

    Great fishing and don’t blow away !!!

  5. Don Barnes says:

    Thanks Very helpful .I can see all the things I have been doing wrong.
    Going to do just as you say . Cannot miss for now I don’t know how to set up. Thanks for your site & info.

  6. I’m new to this sonar mess, and you just answered several questions for me. Thanks for the info!

  7. Just 2 days ago I got an old Eagle 3D-100; have a manual for it, but no power cord or transducer. Anybody know if either the power cord or transducer from any other Eagle models are compatable? Where can these pieces be found?

  8. Chad, Thanks for a great site. I would like to make a comment towards your statement that you were not supposed to get a picture at speed. I too have heard many people say this but if the transducer is placed in such a manner as you said away from the motor and in a good flow of water you can get a picture at all speeds. I use an Eagle unit and it will read at 40+ MPH. many boats have a step at the drain plug,the transducer must be far enough away from this step that it is out the turbulence. Another very important thing is the transducer must be placed so the center of the transducer is on the same plane as the bottom of the boat. This is very important, use a straight edge on the bottom of the boat to be sure it is level. I think it is really most important that your depth finder works at speed because it saves a lot of lower units & props.

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