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Side-Scan Fishing Technology Explained

Side-Scan Fishing Technology Explained

Using Lowrance's StructureScan and Humminbird's Side-Imaging technology is like looking at the bottom without draining the lake.

"With traditional sonar, we wouldn't have known this was anything more than a little hump," said Jeff Williams of Team Catfish Tackle. He pointed to his Lowrance HDS-10 graph screen and the branches of a huge, complex tree beneath the boat.

Limbs showed in the side views on both sides of the boat, and the DownScan view showed that the tree rose well off the bottom.

Williams anchored just upstream of the tree to cast baits downstream to the catfish condo he had found.

Before the last line was even in the water, my son hooked up with a 20-pound catfish -- and that was only the beginning.


Joe Balog, a bass pro who fishes all over the country, said a similar technology, Humminbird's Side Imaging, is also changing the way we fish. "It takes the guesswork out because a rock looks like a rock, and a tree looks like a tree," he said.


Balog runs a Humminbird 1197 on his boat. He likened a Side Imaging view to what you would see if you could take all the water out of a lake and shine a big floodlight on the bottom. Everything in the beam would show up in three-dimensional detail. Shadows would help define the height of objects. And, because the 1197 information is gathered via high-frequency sonar as opposed to an underwater camera, neither water clarity nor available light is ever a factor. The effective area also is much larger than could be achieved with a camera.

But you still have to catch the fish yourself!

When the first "fish finders" were introduced decades ago, anglers heard that fishing would become too easy and lakes would be fished out. That said, the capacity to look on both sides of a boat and see structure, bottom make-up and, in some cases, the fish themselves with unprecedented clarity, creates tremendous opportunities to study lake and river features. It also helps anglers better understand fish and catch fish more effectively.

Many anglers don't associate catfishing and modern technology, but fishing guide Williams makes extensive use of the StructureScan unit, which is an add-on to his Lowrance HDS-10. Instead of simply setting up along the slope at the head of a deep hole, he now places his baits around specific pieces of cover or near concentrations of quality fish that he has already looked at and marked.

Balog also pays close attention to the make-up of the bottom as he utilizes his Side Imaging unit. He has figured out why certain spots always produced fish for him.

"There are some very specific spots where I always catch fish. But I never knew why because nothing really showed up on regular sonar. Now I can see there's a change from sand to gravel or something else that holds those fish, and I can look for more spots like that," he said.

These new technologies calls for a bit of practice. Each angler has to learn to set up a unit according to his own preferences and situation.

Units that offer Humminbird's Side Imaging or Lowrance's StructureScan also have GPS, traditional 2D sonar and various other features. They also work with Navionics mapping chips and can be set up for a variety of screen splits, giving anglers a host of options.

Bass pro Balog generally likes to look out one side of the boat at a time. He'll set the Side Imaging range for 50 feet. For big-picture views, his unit will view up to 280 feet out on each side, but a narrower range gives far more detail on the screen, which usually is more important to him than a broader scope.

The details remain very good up to about 100 feet. So if he wants to search a large flat for isolated structure, he'll set his view for 100 feet.

However, if he were following a channel edge and was looking for specific changes in the bottom make-up, such as stumps along the break, rocks or other subtle features, he would go with the shorter view.

Williams sets up his unit to show both sides. He displays a DownScan view, which shows details of what is directly below the boat. He also sets up his GPS path in a separate window.

Like Balog, he varies the range according the specific situation. When he sees something that looks interesting from the side, he'll scroll over to that spot on his screen and drop a GPS waypoint. Then he'll return to that spot to look at it from another angle or to set up and fish it.

Using a similar approach, Balog has caught several fish from specific pieces of cover he has never run his boat over. If he spots an intriguing-looking boulder or bottom change when he's scanning an area, he'll place a waypoint on that spot, move the boat to within casting range, cast to that specific feature and sometimes catch a fish.

If, however, he had only traditional sonar, he would have been forced to go directly over the spot to study it. That might have spooked the fish below before he even dropped a line.

Balog often begins his search with mapping software. He uses a Navionics chip in his graph to look for contours like reefs and creek channels. Then he goes to those "sweet spots" by running Side Imaging.

Along with figuring out the best configurations for their own applications, anglers must learn to interpret what is on the screen and figure out the positions of features relative to the boat.

The pictures are detailed and accurate to actual shapes. But readings are not always intuitive. It still takes time playing with sensitivity settings and simply looking at things on the screen to see first-hand how longer shadows represent larger objects, what fish look like on the screen and other details, like distances.

As a final note, Balog said if an angler is planning on purchasing a side-scanning unit, he should also invest in the largest possible screen.

"It's worthwhile because a larger screen allows you to see far more detail," he said.

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