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January 14, 2013

Use Side-Scan Sonar to Catch More Fish

Innovative side-scan sonar broadens your view of the underwater realm.

Click through all the images above, too.

A couple of years back, just after side-scanning technology became available, Lowrance StructureScan saved the day for Harry Vernon III and me. We were anchored on a Bimini reef in 75 feet of water, looking for yellowtail snapper. Our chumming ignited a feeding frenzy among amberjack, horse-eye jacks, cero mackerel and sharks; but where were the yellowtails? I had never fished this spot without catching them.

I turned on my Lowrance HDS 10 sonar, activated StructureScan, and set the range to 100 feet. Lo and behold, 30 feet directly off the starboard side of our boat, a large school of yellowtails had amassed. ­Obviously, the larger predator fish in our chum slick had them intimidated. I baited a yellowtail rod, pitched up-current of the ball of fish, and let my bait drift back to them. Wham! Fish on! Had it not been for our ­side-scanning, we would have missed out on our limit of tasty yellowtails.

What Is It?  

Side-scanning sonar is exactly that: a view directly off both sides of your vessel. Viewing the swath of water around your boat is a powerful tool. I’ve discovered bait concentrations that were not visible at the surface; ­significant debris, abandoned crab and lobster traps, large rocks and boulders, shelves, bottom “spikes” and other fish-holding structure. And as described, we’ve located the fish themselves.

Side-scanning devices are offered by Lowrance and Simrad, Navico brands, and Humminbird. Key to ­acquiring the high-resolution imaging associated with side-scanning is high frequency: 455 kHz for greater distance and 800 kHz for greater resolution. The resulting imagery is so crisp and clear that specific fish can be identified as well as bottom structure. What it shows you off to the sides of your boat is amazing. It’s the closest thing to ­diving without getting wet.

Side-scanning hardware is an ­add-on option, complete with its own ­transducer. Humminbird recently ­introduced 360-degree imaging, which enables ­scanning around the entire vessel.

Get to Fishin’!

Without a doubt, it is worth its weight in gold inshore, in inlets and passes, canals and rivers, channels, around docks and bridges, and along the beachfront. Waypoints can be saved; plus, there’s also the ability to measure the size of objects. You can also scroll back to review an attractive piece of structure you had passed by but failed to save.

Captain Mike Holliday, light-tackle guide in Stuart, Florida, uses a Humminbird 998c on his Maverick skiff, and a Humminbird 987c on his 24-foot Pathfinder. “In my area, we fish a lot of docks and bridges for snook,” he says. “There might be a stretch of 20 docks that could hold snook. Instead of going up to each one to have a look, I’ll stay off them, idle along and use side-scanning to see what’s underneath. It’s so unobtrusive and efficient. If I see snook under one dock, I can then set up a quiet approach to catch them, rather than tipping them off to my ­presence by idling up to look around.”

“Same for our bridges,” says ­Holliday. “I’ll make passes along the pilings looking not only for bait, which might tell me which pilings the snook might gather around, but also the snook themselves. Once I discover where they’re stationed, I’ll back off, get into position, and fish that school. This tactic applies to bridge fishing ­anywhere, for striped bass, ­sheepshead, cobia and so on.”

Holliday also uses side-scan for locating tripletail on channel ­markers. These fish often get up tight ­underneath buoys, well hidden from traditional sonar and human eyes. By side-scanning the buoy, and down the chain to its mooring, he knows where fish are holding.