Depth - Fish Finders

Depth Finders, Fish Finders, Sonar or whatever you prefer to call them are your underwater eyes.
Learning to use them, is the key to more catching and less fishing.

Fish Finder knowledge comes from keeping them on and looking at them a lot. You have to have a good idea what they are showing.
For example, if you drop a brush pile, you know how big it is and you generally know where it will lay. Once you know what it looks like on your depth finder, you can use this known underwater, electronic impression and look for other things like it elsewhere.

There are no short cuts to using your electronics.
It is through simple trial and error that you will learn how to understand what your Depth / Fish finder is showing you.

However, some key advice and tips will help speed up the learning curve and perhaps even eliminate some bad habits beginners often develop.
With these goals in mind, let's look into the underwater word.

Should I Auto or Should I Not  Auto ?

Modern LCD or liquid crystal display Depth - Fish finders are computerized and offer a menu-style operating system. The angler presses a combination of buttons to navigate around the menu and access different option until the desired setting is reached and imputed.

Most Depth / Fish finder also have manual and auto settings. By simply turning on your unit you will be using the pre-programmed automatic settings. These include pre-set gain, surface clutter, fish icon indicators and other signal processing settings. My first bit of advice here is to familiarize yourself with the options and the automatic setting pre-sets (Read the owners manual). Doing this will allow you turn off the auto option and further customize your depth finder when you will most need it.

Once you know how to turn off certain auto settings, turn off the fish i.d. or fish icon.

Chad Warford of Lowrance Electronics says while the auto feature is very handy for general use of a depth finder, most upper-level anglers will usually tailor their units to the situations they are seeing the most on the waters they fish.

When you are in manual mode it all comes down to resolution and target separation. Being able to distinguish targets that are six inches apart versus three inches apart allows anglers to see much more. In the auto mode you won't see as many fish and tend to miss much of the total picture.

You actually have get out of the auto mode and then select your upper and lower limits in order to get the better resolution. Just remember, the smaller the window; the better the resolution," notes the marketing director for the Oklahoma-based electronics giant.

Furthermore, Warford says in the manual mode, "ideally you might want a 30-foot window. At this point, separation can be as good as 1/4-inch apart.

Just about any medium to high resolution unit can offer this type of resolution, you just have to know how to set them up.
Warford revealed a little math axiom to check your resolution/target separation no matter the unit.

In 50-feet of water with a 100 vertical pixel unit you divide 100 by 50 and come up with two or 1/2 for a half-foot resolution.
In 60 feet of water with a 240 vertical pixel unit you divide 240 by 60 and get four or 1/4 and discover your targets are separated by a mere 1/4-inch.

Referring to Warford's comments that "the smaller the window; the better the resolution" -- remember when in auto mode, your depth range will be set and reset according to a computer program. Often if you are in 25 feet of water, your unit will choose to scan a range from 0-60 feet. This is not efficient as you are wasting a lot of your unit's power scanning right into the lake bottom. To overcome this problem, switch off of auto mode and set your own depth range - often eliminating the top few feet and stopping the scan about 10 feet below the actual bottom.

Where And How To Mount Electronics For Best Results

What Am I Looking At?

Now that you know how to use all the settings on your properly installed depth finder, it's time to hit the water and go on a fish hunt. Here's what you can expect from a decent mid-level priced unit.

Units that reads with 160 x 160 vertical pixels offers enough resolution to make out both underwater structure and fish. A good unit should also offer something known at Lowrance known as Grayline or at Hummingbird - GrayScale.
This feature activates to let the user know what the density of the object being scanned is - something especially helpful when trying to determine bottom content.

Keeping all this in mind, let's go with a hypothetical, but typical summer time situation and then talk about what to look for in a fall situation as well. With each I will describe what the depth finder is showing and what is actually underneath the transducer.

In the summer, when I am fishing brush-piles 18-24 deep I use my depth finders extensively. I use them, not to find bass, but to locate the brush so I can mark it and then fish it. Working from a bank lineup, I will troll into the area with the depth finder on, scanning the range the brush lies. For dense cedar, beech or pin oak pile I expect to see about a six foot high "lump" on the bottom with a black line on the exterior and a fairly solid "gray" filling. Often, in the early summer and late fall, I will see unordered black scribbles above the brush that indicate suspended crappie or bream. Less dense brush piles of aging or larger oak and iron wood will not have as much gray "filling" on most depth finders and show as black blobs on the bottom.

Remember, I don't see bass in brushpiles.
Use your rod and touch to find the bass, use your depth finder to find their homes.

Where is a good place to look for brushpiles / treetops? Try right around the thermocline on any lake that stratifies. You can see a thermocline on your depth finder by noticing the general trend in baitfish activity and noting the most preferred level it is located.
Right around this depth you will find the thermocline and most of the gamefish in the late summer and early fall.

In the later fall, when fish leave the brush piles and begin to follow vast schools of bait, I use my depth finders a bit differently. Now, I can actually see the bait, as well as the bass, crappie, perch and  stripers. Find large, gray "haystacks" of bait and you have found inactive fish. Find or notice a screen filled with scattered and broken up baitfish and you have likely found feeding gamefish. You will often see bass as well-spaced and unordered black arcs. Perch are small check marks in a vertical formation. Stripers are rarely seen on a depth finder less than 20 feet deep because they are so spooky, though I have seen them when the big motor is off shallower. Stripers are the largest marks you will see on your screen - often an inch or larger in a horizontal layout. You know they were stripers if you saw them for a few moments then they move on and then you locate them again. These fish move fast, so staying with them is tricky at best.

Things To Look For

This fall, try and look for aggressive baitfish configurations mid-way back in the creeks. Here the water will be around 10-16 feet deep and you will actually see the baitfish and gamefish on the screen. How will you know? If you are seeing likely feeding activity on the screen when all of a sudden the water erupts with schooling bass, you will definitely know what to look for next time and consequently start fishing for them before they break.

Once the baitfish move into the backs of the creeks, you really don't need a depth finder, because your eyes and ears will find the fish. You might see them on the screen briefly, but most should be on the surface milling about.

However, later in the year, when the bait and gamefish pull out to the creek mouths and the main lake, you will once again rely heavily on your depth finder. Expect to find huge schools or "haystacks" of baitfish from 10-25 feet down with gamefish below. Every now and then, you will come across one of these bait balls all broken up with the larger arcs mixed in with them. This in when you drop down a spoon or Jig and start catching those electronic fish on the screen.

Study the baitfish carefully and you should be able to note if they are moving upward, downward or remaining stationary. A school with a downward "tail" or trace is moving upward. One with an upward "tail" is on its way down.

My last bit of advice on the use of depth finders.

Buy a good Unit, learn to trust them. Don't chalk up what you are seeing as simply incomprehensible clutter. Study the screen, conditions and lake bottom and more than likely, you will be able to understand what the unit is trying to tell you - there's fish, and lot's of them down there, dummy.

What's next in fishing electronics?

  • Weather radar and instant forecasts appearing instantly on screen?
  • 3-D effect to more easily visualize the haunts of fish?
  • A device that matches the underwater sounds of feeding fish so as to attract fish under an angler's boat?
    Electronic Fish Callers ?

Privacy Notice  I   Glossary of Fish Terms 
By Ben Sanders Charter Striper Guide Lake Ouachita
Ben Sander's
c/1 - 2019

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