Skip to main content

Mapping Bass

Mapping Bass

Serious bass anglers factor mapping into their strategies, but given the never-ending parade of technological advances at our fingertips, it's hard to keep up with the latest ways to chart a course to bassin' success. But those who do reap rewards in terms of fish caught and tournament prowess.

Just ask Scott Bonnema. Whenever the veteran tournament competitor from Zimmerman, Minnesota, hits the water, he has prepared a plan of attack. Lakes are scouted and patterns tested prior to takeoff, and much of his prep hinges on harnessing the latest in sonar and mapping technology.

Total Recon

The first step is priming your plotter with world-class cartography, of which there are many options—with refinements added all the time. But getting the most from charts requires confirming what the contours indicate, plus a fair amount of reading between the lines. Bonnema believes in on-the-water reconnaissance and credits extensive scouting for his string of 2014 tournament successes, which included a B.A.S.S. Nation Tournament of Champions victory on Minnesota's Lake Vermilion, plus a top-five finish and big-bass honors at the Sturgeon Bay Open.

Wherever water clarity allows, he also scans the shallows with polarized glasses in search of promising cover and structure, as well as individual bass. But even in shallow water, he finds sonar a key ally in the quest for bass.

D-I-Y mapping excels for charting complex cover or structure to complement existing cartography.[

Bonnema supplements 2D and down-view sonar with side- and 360-degree scanning options. "Side-imaging is an incredible tool that eliminates having to run over the fish to scout an area," he says. "It creates high-resolution images while you're cruising along, typically at speeds of 2 to 5 mph, at a distance of 60 to 80 feet from objects."

He demonstrated side-imaging technology as we cruised a short cast off the bank of a central Minnesota lake. As we idled along, he pointed out a variety of underwater points of interest, including rocks, logs, weedclumps, and transition areas between sand and mud. "It's a great tool for scanning areas quickly," he says. "When you spot something you'd like to check further, you can slow down and use down-imaging or 2D sonar."

Last May while prefishing for the Sturgeon Bay Open, Bonnema cruised the shallows, both visually scanning with polarized glasses and using side-imaging on his Humminbird 1199ci HD SI sonar-chartplotter combo to pinpoint and mark prime structures. "When my tournament partner Mark Fisher and I began checking the bay, the water was cold and most bass were still out deep," he says. "We figured warming water would bring them in by game day, so we focused on areas we thought would hold fish during the tournament." Believing waves of big smallmouths would soon storm the shallows, they looked for fast-warming bays with ample depths in the 2- to 6-foot range. "We focused on large bays that allowed the fish to be in seven or eight spots instead of one or two, which gave us better odds of being able to fish at least one of the areas properly," he reports.

"We looked for anything that would attract bass or funnel their movements, such as subtle depth changes of 6 to 12 inches, or the edge where a line of rocks transitioned to sand. Key characteristics of spots vary from lake to lake, but certain features tend to concentrate fish. Finding them before the tournament was critical so sonar scouting played a big role."

During another regional team competition in June on Minnesota's Green Lake, Bonnema and partner Bill Bongs parlayed side-scanning intel into victory. "I found a subtle ditch running from a shallow flat into deep water," he says. "I'd fished the area in the past, but had never found the depression on traditional sonar. But when I scanned the break with side-imaging sonar, the trough was unmistakable. It turned out to be a highway for smallmouth bass that were holding deep, then moving onto the flat to feed. In overcast conditions on tournament day, Rapala Skitter Pops and X-Rap Pops scored several big bass there.

He and Bongs moved to offshore humps as the shallow bite slacked in increasing wind. "The key was identifying high-rising structure topped with 2- to 4-foot diameter rocks," he says. "With the boat positioned over 8 feet of water, we cast jerkbaits to 6-foot depths and caught bass after bass. Our Minn Kota Talon shallow-water anchor kept the boat in ideal position without using the trolling motor."

360 Imaging


Bonnema credits his Humminbird 360 Imaging system for revealing prime spots in his September B.A.S.S. Nation victory. "It's amazing technology," he says. "You can scan up to 150 feet in all directions around the boat. Plus, features that allow you to isolate the sweep area, focus on certain views, and adjust resolution or contrast make it even more effective."

Since Vermilion offers largemouth and smallmouth bass, Bonnema tracked down potential hot spots for both species. Looking for largemouths, he avoided hard-hit docks, banks, and easy-to-see timber in favor of overlooked sweet spots in reeds and coontail beds in 5 to 8 feet of water. Sunken logs off also proved productive. "360 imaging revealed subtle details like logs off to the side of the boat, open pockets, and rocks within weedbeds that produced big largemouths on the first tournament day.

"My smallmouth program keyed on offshore reefs with large rocks. During prefishing, I found that boulder-strewn reefs consistently outproduced barren humps. The ability to quickly differentiate the two types of structure from a distance helped narrow my choices among Vermilion's many reefs."

Earlier in the year, Bonnema found that his Bow 360 unit can reveal bass beds lying out of sight of the surface. "In this situation, it's best to isolate the sweep and magnify the view to study the bottom thoroughly," he adds, "zooming in on the beds."

Plotting Along

Garmin GPSMAP 7600xsv

Of course, sonar discoveries are fleeting if you don't save their locations. "It helps to mark points of interest with icons that help you to recall them months or years after you find them," Bonnema says. "Take time to choose symbols and names that mean something, and will help you remember what a waypoint is. For example, I use a Red Cross symbol to mark spots where I can 'get healthy' in a hurry if I'm struggling in a tournament. I also use small symbols for boat position, larger ones for structure."

When charting key cover or structure, Bonnema advises highlighting both the spot you expect to hold fish and where you should position your boat to work that spot. "Determine the angles at which you want to present your lure," he says. "Consider how wind, waves, and the position of the sun can affect how bass position in relation to cover and structure. And in clear, shallow water, long casts can be key, so keep your boat as far from the fish as possible."

Toward that end, he often adds "Casting Rings" to his charts. "They allow you to stay a set distance away from your target," he says. "Say you find a boulder along a breakline and want to cast to it without driving over it. Humminbird's Casting Rings feature allows you to create a circle up to 150 feet in diameter around it. When you come back to fish the boulder, keep your trolling motor on the casting ring and you can calculate exactly how far away you are from your target."

Other handy mapping tools include LakeMaster's Depth Highlight feature, which lets you highlight depths lakewide once a pattern is established. For example, if bass are feeding on 10- to 15-foot flats in one area, you can highlight similar areas in that depth range, even set boat-positioning waypoints on them to guide your casting attacks.

In a similar vein, high-tech systems, such as Humminbird's i-Pilot Link and MotorGuide's Pinpoint Connect, integrate your sonar, GPS, and trolling motor to lend a hand at the helm when hovering on spots or following preset trails, so you can focus on fishing. Functions such as Humminbird's Follow The Contour and Contour Offset allow you to trace and hold your boat a set distance from key contours, engendering hassle-free navigation.

Humminbird AutoChart Live

DIY Mapping

Finally, do-it-yourself mapping has become a reality, thanks to offerings from LakeMaster, Navico, Navionics, and others. Many excellent fisheries, typically small or remote, remain unmapped or mapped poorly. The ability to create your own detailed lake maps from sonar recordings is valuable. Moreover, these systems allow anglers to record depths as they fish or drive the boat, and the data can be uploaded to an account, where it is used to improve the accuracy of existing maps. Bonnema says D-I-Y mapping excels for charting complex cover or structure to complement existing cartography, and is immensely beneficial when fishing waters with limited coverage—small or remote lakes and many rivers.

Some systems, such as Navico's Insight Genesis, offer depth-shading options, the ability to merge multiple maps into a master chart, and online storage of your mapping library. You can even scrutinize your new map against the sonar soundings that created it, to check things like vegetation density and the presence of baitfish.

Granted, excursions spent charting and recording key structural features take time from actual fishing. And many of the systems require time in front of the computer, downloading and uploading files. But the payoff is amazingly efficient fishing once you hit the water, which usually means more bass per hour.

Get Your Fish On.

Plan your next fishing and boating adventure here.

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

Recent Videos

In-Fisherman Magazine Covers Print and Tablet Versions

GET THE MAGAZINE Subscribe & Save

Digital Now Included!


Give a Gift   |   Subscriber Services


Buy Digital Single Issues

Magazine App Logo

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Buy Single Digital Issue on the In-Fisherman App

Other Magazines

See All Other Magazines

Special Interest Magazines

See All Special Interest Magazines

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Get the top In-Fisherman stories delivered right to your inbox.

Phone Icon

Get Digital Access.

All In-Fisherman subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now

Enjoying What You're Reading?

Get a Full Year
of Guns & Ammo
& Digital Access.

Offer only for new subscribers.

Subscribe Now