Side-Scanning Innovations in Fishing

Side- and down-scan sonar imaging open new windows in fish finding

November 19, 2011
side-scanning sonar
Side-scanning sonar Fole Photo

The pictures of the geography — and the fish — beneath our hulls generated at the helm are undergoing a rapid transformation, perhaps bigger than anything since the MFD replaced the paper recorder. This is already evident in the CHIRP fish-finder technology, introduced last year by Garmin and Simrad. Affordable side-looking sonar offers up nearly photographic images of what is off to the side of and beneath a boat.

Side scanning employs a narrow sonar beam at a low output to create a high-resolution underwater picture. The result is an extremely detailed composite image on the MFD. Available gear ranges from integrated machines, like Humminbird’s Side Imaging and Down Imaging, favored by inshore anglers, to combined side- and down-looking modular scanners, offered by Navico’s Lowrance and Simrad as StructureScan. Top of the heap is WASSP (Wide Angle Sonar Seafloor Profiler) technology, by ENL, a New Zealand company whose products are now handled in the United States by Furuno. WASSP can literally construct 3-D bathymetric charts complete with fish.

With the range of side scanners available, you can get as much sophistication in this technology as your wallet can handle.

Humminbird side-scanning sonar
In this Side Imaging screenshot from Humminbird, a cloud of bait is clearly visible at the right of the screen, hanging above the wreck on the bottom. Courtesy Humminbird

Essential View

Humminbird produced one of the first side scanners adopted by saltwater anglers, who found it invaluable for fishing shorelines, docks and bridge pilings. It didn’t take long for the side scanners to find a home offshore as well, especially after the recent addition of the Down Imaging component. The saltwater-friendly 1100-series sonar (from about $2,400) uses a thin sonar beam to assemble a “sonar snapshot,” as the company describes it, of the area up to 240 feet to the left and right of and beneath the boat.

Capt. Sam Heaton of Stuart, Florida, relies on the Humminbird 1100 series both inshore and offshore. “When trout fishing with Side Imaging, I can see the weed beds and the holes in the flats,” he says. “Side Imaging is the best thing to come along in inshore fishing in the last 25 years.”

The open-water range of Side Imaging is about 100 or 150 feet, says Heaton. But that is plenty when you are looking for bait, which is a big part of the way he uses the gear offshore. “All my nearshore wrecks are within that depth range,” he says. “Looking for bait last week, we pulled onto the David T wreck. The current was screaming, and nobody was there. I ran over it with the Side Imaging and could see the bait clearly right there, suspended at 65 feet on the down-current side of the wreck.”

Bathymetric Library
his chart of the seafloor generated by WASSP accurately depicts the geography as well as the fish, shown here by the cloud of red and blue dots that appear suspended over the bottom. Such charts can be archived for later reference. Courtesy WASSP


Taking it one step further, Navico’s StructureScan (starting at about $600), available under both the Lowrance and Simrad names, adds a down- and side-looking module to its MFDs that has an effective range of 200 to 300 feet, says Navico’s Gordon Sprouse. With a pair of bronze through-hull transducers connected by a Y cable ($1,199), the unit produces right- and left-looking images, which overlap to create an additional image of what is directly beneath the hull, with the same extreme detail and resolution. And because it’s a black-box system, the fast redraw and data handling approaches real-time imaging.

“At trolling speed, you can clearly see bait,” says Sprouse, “and when you make a turn, you do not get any smearing effect because the MFD is not burdened with the requirement to process that image. The black box processes a lot of data very quickly.”

And while the resulting image offers a substantial wow factor, Sprouse says, it also makes things much simpler for the angler. “It is easy to interpret,” he says. “You spend less time figuring out what you are looking at, and you have the ability to identify structure, place your cursor on it and save the waypoint, so you spend less time trying to orient yourself to the structure.” Which means you spend more time fishing it.


In Depth

For maximum-quality construction of an underwater picture, the WASSP is like a “side scan on steroids,” says Furuno’s Jeff Kauzlaric. WASSP technology comes in a couple of different configurations, neither for the casual or budget-minded angler. The least expensive setup, a 60 kHz model, starts at around $40,000. That’s a big piece of change, but one that some sport fishermen find well worth the outlay, says Furuno assistant product manager Steve Bradburn.

High-stakes tournament fishermen and wide-ranging anglers, who roam where charts are lacking or poor, such as deep into Mexican waters, are a couple of the kinds of anglers who find it money well spent.

WASSP units utilize a 120-degree transducer cone that maps everything it sees under the boat in high resolution. “You see holes, ledges and fish schools in three dimensions,” says Bradburn. “When you go over something with it, you are creating a chart.”


It’s in a different league from the other side scanners, he says. This is a black box that hooks into a laptop computer and operates on a navigation-software platform rather than a chart plotter. You buy the WASSP system, and you get the Navigator program, which uses Navionics Gold for a base. Charts created on the system can be filed and pulled up as needed for reference.

Plotter integration is not out of the question. Given Furuno’s access to MaxSea and Time Zero technology, the addition of WASSP to the picture may well push fish finding into uncharted territory in the near future.


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