Dams can be daunting. So much water and so few fish! And unless you’re fishing structure such as fallen timber or you’re tossing a topwater into a sheltered cove at the break of day, then you’re going to need some assistance in finding where the fish are.

Or, more importantly, you’re going to have to know where the fish aren’t. You need to whittle that massive body of water down to the most productive zones on the day you’re fishing.

Your depth sounder or fish finder, used correctly, can narrow down dramatically the area you’re searching for fish. After all, those who say that the fish are a bonus when you go fishing just aren’t keen bassers!

THE REAL BASICS

Originally called ‘sonars’ (at least until ‘fish finders’ became a more marketable name), these units basically bounce sound waves off the bottom - and everything in-between - and display the results in a graphical form on the viewing screen.

The fine detail about how this is achieved is really not as important to understand as how your unit is presenting that information to you. Consequently, what we’ll piece together here is what’s down below - be it bass, boulders or breaklines - and then make that link to what it looks like when your sounder sees it.

What most bassers need to be able to do is to be able to take the information that their sounder’s showing them and from that, picture the terrain they’re passing over.

It takes a little time to learn, but acquiring that skill is mandatory if you want to catch more bass. And that’s the truth.

SETTING UP

Before we hypothetically head out on the water for a sounding session, we first need to make sure that our unit’s working to the best of our advantage.

As to be expected and in general, the more money you spend on a fish finder, the better it will serve you. Currently, I think that you need to spend at least $700 to $800 if you’re serious about your bass fishing and you want a unit with the highest possible pixel count on its screen.

More specifically, you want a unit that has a heap of pixels from top to bottom, as I believe that this is the singularly most important feature in a unit. More pixels equals a better picture of the terrain that you are searching and the better the picture, the less guesswork is involved while interpreting the data that’s presented to you.

In thia article, we’ll be taking a selection of current model sounders in the class that we’re looking at for a test drive, so if you’re looking at buying a new unit or upgrading your old one, you might just have to wait a little for that information.

What we can do now, though, is look at how to best set up your sounder for bass fishing and what the hell all of that information means.

RAW DATA

Like it or not, fishing competitions and tournaments have essentially forced anglers to learn what their sounder is telling them. Competitors know that the fish are in the impoundment and their first challenge in a session is to locate where the fish are. Only then can a competitive basser tailor a strategy to get the fish to bite.

Raw data screens show bass - like these half-dozen prime specimens - relatively sized. You can tell big bass from small bass.

And the consensus of these super-keen anglers is to run their units with any fish icons or fish identification turned off.

“I don’t know of too many anglers who finish in the top ten of any of the BASS events that search for fish with the icons turned on,” says two-time BASS Angler of the Year, Brett Thomson.

“It’s definitely possible to differentiate between bass and other species by the way that the raw data appears on the screen,” he adds, “and on most units, you can tell the difference between small and big bass, which is important when you’re trying to upgrade.”

Five time BASS tournament winner, John Schofield, echoes Thomson’s sentiments.

“My eyes are glued to my sounder for nearly the entire time that I’m fishing in impoundments - either in tournaments or socially. Modern LCDs don’t just let you know where the fish are, they let you know what mood they’re in,” Schofield says.

So the first step towards sounder proficiency is to turn off your fish-icon settings and concentrate on the raw data.

SITTING STILL

Imagine that you’ve just launched your boat on Somerset Dam, one of Australia’s best impoundment bass fisheries and one where intimate knowledge of your unit is essential to success. You’ve turned your fish-icons off and you’re drifting around a couple of hundred metres off the boat ramp. What do you do?

If we’re not moving and the fish isn’t moving, then there’s no way that the fish will make an ‘arch’ or a ‘slash’. It’ll display as a constant signal and show as a solid line across the screen for as long as it is within the range of coverage of the transducer.

First you have to adjust the ‘gain’ or ‘sensitivity’ of the unit to suit the ambient conditions. Although your unit will detect echoes from nearly everything in the water column - from snags and fish to plankton - you can manually set the limit of what you see.

Increasing the sensitivity setting of your sounder means that more information is displayed on your screen and a maximum setting usually means that the display is plastered with every piece of plankton and every scrap of interference in the water column. Try it and see what I mean.

Decreasing it has the opposite effect and gradually information that can be useful is filtered out until you reach the minimum adjustment. At your minimum setting you might see someone swimming under your transducer and not much else.

Most bassers reach a happy medium when the screen just starts to show a little clutter. On Somerset, you’ll most probably see the boundary between the warmer surface layers of water and the cooler depths - called the thermocline - between 15 and 30 feet down. This layer is usually marked by an aggregation of plankton and baitfish that suspend right at the junction.

Naturally, fish tend to hang out there too. But what does a fish look like with the fish icons turned off?

Let’s imagine that there’s a single, stationary fish suspending above the thermocline when we’re sitting still. If we’re not moving and the fish isn’t moving, then there’s no way that the fish will make an ‘arch’ or a ‘slash’. It’ll display as a constant signal and show as a solid line across the screen for as long as it is within the range of coverage of the transducer.

If you drift off the fish, the line will disappear and if you drift across another, another line will start.

Multiple fish show as multiple lines and indeed, a whole school of bass aggregating under the transducer can effectively ‘black out’ the screen in the range of depths that they’re holding.

“When you see multiple bass under the boat, you know that you’re in for a good time,” jokes BASS Pro angler Tim Morgan. “And I don’t really know why, but a lot of the time, bass will make a habit of schooling under the boat - especially on calmer days and after you land a bass. Maybe it’s the shade under the boat, or maybe the boat just acts as a FAD on a featureless flat?”

Toowoomba guide Jason Ehrlich has similar theories.

“I think that bass are actually attracted to the noise of the transducer,” Ehrlich commented at a recent tournament. “I know that when I sit over suspended fish in Cressbrook’s thermoclines, it’s only a matter of minutes until there’s a school around 20 feet under me. After that it’s easy to catch them on fly, tailspinner or ice-jig,” he said. His top-ten placing at a recent tournament confirmed his hunch.

ON THE MOVE

It’s no good having a good idea of what a bass looks like under your boat if you can’t find one in the first place, so the next skill you’ll need to hone is detecting what a fish looks like while you’re on the move.

A Humminbird's 'flat' beam will show bass as slashes rather than arches. See bass like this, and you know you're in for a good time! This shot was taken idling across the flats on Somerset's Bay13.

To see fish, however, you’ll need to be travelling slowly enough for your unit to illustrate the fish on the screen. At planing speeds, you may still get good bottom definition and be ably to broadly pick up the thermocline clutter, but your chances of identifying individual fish are nil.

You need to travel at a speed where fish are depicted with multiple pixels. Idle speed or just above it works well.

The shape that fish and bottom structure takes while passing over it depends on the shape of the sound beam that your unit sends out. If your unit shoots a cone-shaped beam, fish will often appear as arches - the wider the cone’s angler, the bigger the arch. The compromise is reduced bottom definition.

Alternatively, some units utilise multiple or flattened beams that give much better bottom definition and more accurate depictions of suspended items, but rarely display a comforting arch.

If that’s all a little difficult to understand, just go trolling. Seriously. Trolling is a good way to make the link between what you’re seeing on your screen and what it equates to in the water.

What you are doing is travelling at a speed that you’d prospect at and if you know the depth at which your diving minnows are swimming, then you can make the link between what you see on your screen and what’s biting your lures. If you catch a couple of fish and think that you can identify more, then try sitting over them and getting them to ‘flatline’ on your screen.

Once you can do that, you’re well on the way to confidently idling along and making informed decisions about what’s below.

BUT WHERE DO I START?

So is finding bass just a matter of randomly idling around a dam and hoping that you see a few fish on the screen? If you have endless time and patience it can be, but there are several types of structure in most impoundments that are good places to start.

You’ll read heaps of articles in fishing magazines outlining specific structures and strategies, but often, factors dictating where the fish are concentrated in the impoundment are as varied as whether the dam’s rising or falling, season, time of day, baitfish available or whether the dam’s ‘rolling over’.

If you don’t have a feel for where to start or you can’t get any reliable local information, there are always several places in a dam that are worth checking out on the way to cracking the pattern for the day.

Points that jut out into the dam are always prime locations. It seems that you can nearly always find a fish or two adjacent to this major structure. Make sure you sound across as well as along points, as sometimes bass will school off the end of a point and at other times, they will sit near the bottom right along it.

Flats are large areas with no rapid depth changes. Bass in particular will often school over flats with no noticeable structural reason. At other times, they will be scattered across these areas and can be targeted with various techniques. Both of these patterns are easily detected at slow speeds with your sounder.

Breaklines and areas adjacent to the old river beds are favourite structures for trollers and these areas are ideal starting points when sounding the open water.

Laydown or horizontal timber in the shallows is a traditional structure to fish, but in impoundments that have not been cleared before filling, you can find good laydowns on your sounder. In this case, you may not be looking as much for the fish as you are the structure, and then you can fish it accordingly.

Part two, we’ll take a range of popular models for a spin and we’ll illustrate the results that will help you gain an objective view of what’s on the market, and how it will suit your needs. Stay tuned.

Continue to part two