Using Your Electronics to Catch More Fish: AIS, Autopilot, Chartplotter, Radar, and Sonar

There is a lot more to effectively using your electronics than merely staring at your fishfinder screen. Use these tricks and tips to boost your catch.

19th May 2013.
By Lenny Rudow

When I tested the new Raymarine Dragonfly a few months back (read Raymarine Dragonfly: A Whole New Breed of Fishfinder) it was a shocking reminder of just how far our sonar systems have come. I remember squinting at the fishfinder screen when it consisted of two fuzzy blinking lights; squinting at it when it was a fuzzy paper graph, and squinting at it when it washed out in any kind of sunlight. With the Dragonfly, I squint at it only because my eyes have aged quite a bit since the days of flashers and paper graphs.

Today’s units have advanced even faster than my eyes have deteriorated, with screens that are far brighter and clearer. There’s just one problem: many of us have grown over-dependent on those screens, and we fail to see the many other ways we can use electronics to help us catch more fish. Want to use every tool to your advantage? Then don’t forget to put these items to work.

fishing with electronics

You want to catch more, bigger fish? Of course you do - and modern marine electronics can help!

1. AIS – To heck with collision avoidance—catching fish is a lot more important, right? And AIS (check out AIS Basics: Automatic Identification System Explained to find out more about this system) is another useful electronic item for anglers. The trick is using it to locate boats and ships that could be holding fish. In the Chesapeake Bay, for example, striped bass and sea trout often congregate under ships sitting at anchor, waiting for a berth to open up in the ports. All along the Atlantic coast commercial squid ships and scallopers are often followed by bluefin or Yellowfin tunas. And in the southern Atlantic and Gulf, shrimp boats are magnets for a wide range of gamefish. You can use AIS to pinpoint these fish-magnets, and stop wandering around the ocean looking for needles in the haystack.

2. Autopilot – Most modern autopilots can give anglers a serious edge over the competition. Those with a CT (contour track) or DTC (depth contour track) feature on your unit are best, since you can set them to follow a productive drop-off or edge you’re trolling along. Another way to harness the fish-catching ability of autopilot is to set it to steer along in relatively tight “S” curves. Gamefish often strike lures trolled near the surface as they cross over the boat’s wake and enter flat water, and maintaining a steady stream of S’s is a lot easier to do by pressing a button, than is it by baby-sitting the wheel. Finally, make sure you know how to use the clover-leaf pattern setting in your autopilot. When you locate a hotspot, trolling a clover-leaf pattern over it is almost always the best tactic; every time you cross where a “leaf” meet at the “stem” you hit the hotspot, and if the fish are moving, whichever direction they go in will be covered by one of the leaves.

3. Chartplotters – This little box of knowledge can do a lot more than get you where you’re going and show you what the bottom contours look like when you get there. They also come in quite handy for drift fishermen, thanks to the anchor alarm. Yes, an anchor alarm is actually a fishing tool—no matter what those cruisers and sailboaters may think. When drifting over a shoal, wreck, reef, or other structure, set your anchor alarm to go off once you’re 50 or 60 yards or so away from the hotspot. This will end the common mistake of drifting for too long over unproductive bottom, when you get a bit lazy or forget to keep track of your exact position.

Another way chartplotters come in handy is for tracking temperature breaks. Sure, it’s easy to locate the approximate position of a break by looking at SST charts, from the comfort of your own home. But unless your boat gets a constant satellite feed, once you shove off you won’t be able to track that break. And it’s common to find a break, fish it for a while, then lose it. The solution? Dedicate a unique waypoint icon in your plotter; when you first find a break, plug in a mark with that icon. Then as you troll back and forth across the break, plug in that mark every time you cross it. Soon you’ll have a history that will tell you the break’s boundaries, the speed and direction it’s moving in, and—assuming you also have a waypoint icon dedicated to indicating where you have strikes—how the fish are relating to the break.

mahi mahi fishing

Shortly before hooking this mahi-mahi, the captain spotted the lobster pot float it was hiding under on radar.

4. Radar – The most obvious way anglers use radar is bird-spotting. This is, however, a vastly over-rated practice. Relatively few radar units are sensitive enough to use for the task (Broadband radar being a big exception; read Choosing the Right Radar to find out if it’s a good option for you) and in many cases there will be too many boats, buoys, and other screen-cluttering items to figure out whether you’re looking at avians or other anglers. You can, however, use radar to spot lobster and fish trap buoys from afar. And remember, mahi-mahi love to hang out around those buoys.

You can also use radar to keep tabs on the competition. It’ll show you congregations of boats and more importantly, it can help you find boats that don’t want to be found. A few years back, for example, I heard a couple of captains talking on the VHF about huge schools of baitfish, white marlin milling around them, and constant hook-ups. Both boats were racking up the numbers, and neither was about to give away their location over the radio. But I heard them discussing a freighter which was passing close by. A quick peek at the radar screen showed that there was only one very large target (the freighter) within both VHF and radar range, about 12 miles to my south. Two smaller targets near-by were the fishermen. Half an hour later, I was in on the hot bite.

5. Sonar – Yes, this one is, naturally, the biggest help of all. But there are some ways to use your fishfinder which go un-tapped by most anglers. One is water temperature readings. Sure, you can look at the number in the corner of your screen. But unless you keep a hairy eyeball on it at all times, you’re bound to miss abrupt changes. Savvy anglers will ditch the numeric temperature display in favor of a graph; nearly all fishfinders have ‘em these days. Then, they can check the graph’s history now and again to look for anomalies they may have missed while cruising or trolling.

Finally, don’t forget to use your sonar to look for thermoclines. These underwater temperature barriers often dictate the depth the fish will be holding at, and if you can find a solid thermocline, you’ll know where to set your baits or lures. Thermoclines usually appear as broken, spotty marks at a more or less consistent depth. To find them, turn your sonar’s sensitivity up until the screen is un-readable with clutter. Then turn it down bit by bit, looking for that shadowy underwater line. If none appears before you’ve toned out all the clutter, you’re probably not over a thermocline. If one does show up, however, re-set your lines to match its depth.


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About the author:

Lenny Rudow

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Lenny Rudow is Senior Editor for Dominion Marine Media, including Boats.com and Yachtworld.com. With over two decades of experience in marine journalism, he has contributed to publications including Boating Magazine, Marlin Magazine, Boating World, Saltwater Sportsman, Texas Fish & Game, and many others. Lenny is a graduate of the Westlawn School of Yacht Design who has won 28 BWI and OWAA writing awards.
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