Radar ranks as one of the greatest inventions of the 20th century, having served as a critical advantage for Allied Forces in its first trial by fire during World War II. Today, marine radar also lends boating anglers critical advantages.
While most boaters think of marine radar strictly as a tool to help navigate when visibility is limited, today’s advanced models also help you find signs of fish beyond visual range. Let’s look at some examples of how this works for you.
Finding the Fleet
One angling advantage of radar hit home for me on a summer offshore trip with Capt. Gary Adams of Rail Time. We were after albacore 40 miles off the Southern California coast. Yet, as the morning wore on, it appeared that we might go home empty-handed. Then Adams fired up his radar and extended the range to 24 miles, and suddenly found a cluster of faint, yet stationary, targets about 15 miles due west.
He recognized it as the San Diego sport-fishing fleet, and the lack of movement indicated they were on fish. While the fleet skippers maintained radio silence to keep others from discovering the hot spot, they couldn’t hide from radar. Adams used the radar’s Electronic Bearing Line (EBL) feature to determine a course, the Variable Range Marker (VRM) to confirm the distance, pulled in the lines, and ran for the action. Within an hour, we too were in the middle of a foaming albacore bite, and quickly loaded the boat with 30- to 40-pound longfins.
Radar lets you find and follow the offshore fishing boats in other ways too. Features such as Automatic Radar Plotting Aid (ARPA) and Miniature Automatic Radar Plotting Aid (MARPA) track targets. “Essentially the same thing, ARPA and MARPA automatically track the course and speed of a number of targets, so you know exactly where they are and where they are heading,” says Jim McGowan, marketing manager for Raymarine.
Though designed to help avoid collisions in limited visibility, these features also tell you, for example, if a boat is trolling or running at speed, and if it suddenly stops while trolling — an indication of a hookup. That’s the kind of information that leads you to productive offshore areas.
“A good way is to put two or three targets within a fleet of boats into your ARPA,” says McGowan. “If they are moving at high speed, they are probably not fishing. But if they are going slow or standing still, there is a good chance they are on fish.”
A radar/chart-plotter overlay serves as another tool in your angling arsenal. “This feature places a live radar image on top of an electronic chart,” McGowan explains. “The returns are semitransparent, so you can also see the chart features, land masses, bottom contours, and your waypoint icons underneath the radar images.”
One way I have used the overlay feature is to learn if another boat is fishing a distant wreck or another spot on my waypoint list at any particular time before deciding to go there myself. If there’s radar return over the waypoint icon on the chart, it’s a sure sign that another boat is fishing it, so I look for an unoccupied spot.
A radar overlay helps guide you to the depth or contour line where fish are feeding. For example, while targeting sailfish off Islamorada a few months ago, I used the radar/plotter overlay and noticed that nearly all of the boat targets were lined up in 90 feet of water, even boats beyond our vision. Armed with this information, we worked our way to the same depth and found fish.
To use features such as chart overlays, ARPA and MARPA, the radar must be networked with an electronic heading sensor and a GPS. Most fishing boats today have GPS, and a boat with an autopilot also has a heading sensor, such as an electronic compass, which serves double duty with the radar. NMEA 2000 plug-and-play cables make networking simple.
For the Birds
It’s no secret among savvy captains that you can find flocks of birds at a distance with marine radar. And flocks of birds often mean schools of feeding fish.
“You can pick up bird flocks with any radar, even low-power dome models, as well as with open-array antennas,” says McGowan. “But it takes a lot of practice to tune the radar and recognize the signals.”
With many models, the best method is to turn up sensitivity until the screen fills with clutter, and then dial it back 2 or 3 percent, according to McGowan. “Practice when you have visual sight of the birds to see what they look like on your radar,” he advises.
Raymarine has a feature that takes away much of the guesswork. “All of Raymarine color radars have Bird Mode,” McGowan explains. Digital-signal processing automatically adjusts the sensitivity and recognizes birds on the system without obliterating the radar screen with clutter, he says. As a result, bird flocks show as bluish clouds on the display.
The distance at which you can “see” birds depends on the type of radar and its antenna. Low-power radars with dome antennas read birds out to about 5 miles. More-powerful radars with open-array antennas detect birds at more than twice that distance.
Radar helped win WWII for the Allies, and today’s advanced radar systems continue to stand guard over our nation and preserve our freedoms. It’s nice to know that same technology also puts you on fish.