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Savvy sport anglers are using professional-grade sonar systems to locate tuna and other species.

Savvy sport anglers are using professional-grade sonar systems to locate tuna and other species.

I’ve danced this dance hundreds of times, yet it never fails to make my pulse race. “Throw it steady off the port side,” the captain’s voice crackles over the loudspeaker. The deckhand pitches one or two live sardines at a time over the side as the boat turns to intersect an unseen quarry. “Here they come, boys — let ’em have it!”

A few nets full of live anchovies and sardines are launched off the stern, followed by a synchronized volley of casts lobbing hooked live baits into the fray. The water erupts with boils as frenzied tuna crash through the chum with open maws. Anglers whoop and holler, first at the sight and sound of the boils, then as tuna slam their baits and bend their rods into heavy arcs.

My older brother, a lifelong angler and Vietnam vet, once compared offshore tuna fishing to combat: hours of boredom punctuated by moments of mayhem, screaming and blood. I’ve always accepted this as a fairly accurate description of Southern California party-boat tuna fishing — at least from the angler’s perspective. Up in the wheelhouse, however, it’s a different story. What seems like hours of mindless driving and trolling is often a high-tech cat-and-mouse game, with advanced sonar technology used to hunt fast-moving schools of fish.

Much like a scene from every submarine movie ever made, the captain at the helm is focused on his vessel’s sonar system, scouring swaths of the water column to find and intercept tuna. Sonar’s ability to see 360 degrees around the boat and detect individual targets or schools of fish from a quarter-mile or more away has given commercial fishermen and charter skippers a huge technological edge for decades.

During the past few years these advanced systems have become more common on recreational fishing boats — and not just megayachts. In skilled hands this technology has become nothing short of a revolution for serious anglers looking to up their game.

California angler Paul Meltzer installed a Koden KDS-6000BB on his 68-foot Buddy Davis, Kodiak.

California angler Paul Meltzer installed a Koden KDS-6000BB on his 68-foot Buddy Davis, Kodiak.

What’s In a Name?

Sonar originally was an acronym for sound navigation and ranging; today’s modern equipment traces its origins to naval technology developed to hunt and destroy enemy submarines. In recent years, however, marine electronics manufacturers have applied the term sonar loosely to describe various types of echo sounders, from traditional straight-down fishfinders to technologies that scan the bottom on either side of the boat. Although these systems provide useful information and help anglers locate fish and structure, they are not the same as commercial-grade sonar.

There are several important differences between the two. True sonar systems use a transducer tube (usually 6 or 8 inches in diameter) and a hydraulic or screw-operated hoist that lowers the transducer unit below the hull during operation. During high-speed running, the hoist raises the transducer into a sea chest. True sonar can search horizontally around the boat in a full circle, and it shows fish or structure targets on a radarlike display. It also alerts attentive captains to the presence of fish through audible tonal differences, even if targets don’t necessarily appear on the screen.

True sonar systems require complex installations and can range from about $14,000 to $75,000, just for the equipment. Sonar systems available to recreational fishermen fall into three general categories: searchlight sonar, sector sonar and omni sonar. Searchlight sonar systems, such as Furuno’s CH-270 (about $14,000), utilize a beam as tight as 6 degrees (like the beam of a flashlight) and mechanically steer it to sweep as far as 360 degrees around the boat. Because this type of sonar waits for a return before moving, it can take more than a minute to complete a full circle when set at a maximum range of 2,500 feet. This lag to complete a full circle — known as a “train” in fishing parlance — can be problematic when chasing fast-moving fish offshore. However, operators can reduce the time significantly by using shorter range settings or reducing the area to be searched to forward of the boat only. And although searchlight sonar does take longer to complete a train, its sharp, narrower beam is less likely to miss dispersed or hard-to-mark fish targets.

A school of bigeye marks ahead of the boat on this professional-grade Furuno system. 

A school of bigeye marks ahead of the boat on this professional-grade Furuno system. 

The Hardware:

The Furuno CSH-8L Mark-2 omni sonar

The Furuno CSH-8L Mark-2 omni sonar

Wesmar, the sonar brand that is pretty much standard equipment aboard the San Diego-based charter fleet, is also seeing more of its new HD-860 searchlight systems being fitted aboard private sportfishing yachts. This system includes gyrostabilization of the sonar beam to improve performance in rough weather. It sells for about $18,000.

Sector sonar systems, such as the Furuno CH-37BB and Koden KDS-6000BB, can be tuned to read larger sectors of water at a time, shortening the time required to complete a train at longer ranges. The Furuno CH-37BB, for example, can be set to a 45-degree-wide sector at ranges to 6,000 feet. It retails for about $45,495. The Koden KDS-6000BB can be set to four sector angles up to 20 degrees and has a scanning range of 3,000 feet. It retails for $14,999. A true broadband sector sonar, the KDS-6000BB adds the unique ability to adjust the output frequency from 130 kHz to 210 kHz in 0.1 kHz steps, by turning a dial. This feature allows the operator to fine-tune sonar performance on the fly, based on the conditions, situation or type of fish he’s hunting.

Furuno’s CSH-8L Mark-2 omni sonar is a different animal altogether. With this system, a stationary transducer shoots in all directions at once, providing a 360-degree reading that shows returning targets in real time. The fact that there is no waiting for the display to update as the system sweeps around the boat is an advantage for fishermen wanting to locate, track and keep up with fast-moving fish, even when the targets are far away. The CSH-8L Mark-2 has a maximum range of 5,000 feet and sells for about $75,000.

For commercial fishermen or charter captains who earn a living catching fish, this sophisticated equipment is simply a cost of doing business. For the recreational angler and boat owner, however, a sonar system is more of a luxury option — albeit an extremely useful one.

The Koden KDS 6000 broadband sector sonar

The Koden KDS 6000 broadband sector sonar

Given the cost of the hardware, the installation, which can run into tens of thousands of dollars, and the physical space needed to accommodate the sonar hoist, it’s easy to see why this technology isn’t for every private-boat angler. Still, these systems are finding their way aboard more vessels owned by recreational anglers who fish seriously and competitvely.

There are several factors behind this sonar revolution, and they vary, based on geography. Off California, the fourth straight year of trophy bluefin tuna — and their continuously escalating size — has created a fervor among private boaters. And although they have certainly enjoyed some success, it’s a much tougher game when you’re limited to what you can see above water. If there are no visible signs, such as working birds or jumping fish, anglers just hope to intersect a school randomly with their trolling lures or drive over some fish with a straight-down sounder. It’s just not the same as actively hunting with serious sonar.

Monterey, California-based lawyer Paul Meltzer installed a Koden KDS-6000BB on his 68-foot Buddy Davis sportfisher, Kodiak. From his home base in Santa Cruz, Meltzer fishes inshore and offshore waters, chasing anything from rockfish along the rugged coast to tuna on the offshore banks. An avid angler and surfer, he frequently takes Kodiak on long-range excursions far down the Baja coast to such famous fishing grounds as The Ridge and Hurricane Bank. There, much like San Diego’s luxury long-range fleet, Meltzer utilizes Kodiak’s sonar to find and catch giant yellowfin tuna, wahoo, dorado and yellowtail.

Meltzer is more hands-on than typical yacht owners in that he runs and maintains his vessel. For this reason it was important that his new sonar be easy to understand and operate. “The fact that the KDS-6000BB has a streamlined hoist unit and is easy to run, even for new operators, has made it more and more popular among sport anglers,” says Allen Schneider, vice president of sales for Si-Tex/Koden. “We even put a system on a 33-foot Grady-White in California.”

Todd Tally, general manager of Atlantic Marine Electronics, has a slightly different perspective on what’s driving sonar sales, but it still boils down to familiar themes of competition and the desire to catch more fish. As a wholly owned subsidiary of Viking Yachts, AME has installed many Furuno sonar systems on high-end sportfishing boats up and down the East Coast. The majority of the systems have gone to Vikings, but Tally has also helped put sonar on other boats, including a Winter 65 and a Jarrett Bay 90. Although the first wave of sales was primarily searchlight systems, Tally has seen a shift to omni-sonar technology. He credits Jason Buck, captain of the Louisiana-based Viking 70 Done Deal, as an early adopter of Furuno’s omni-sonar technology.

Capt. Pat Cavanaugh (left) and the Pacific Dawn crew with three 200-plus-pound bluefin tuna.

Capt. Pat Cavanaugh (left) and the Pacific Dawn crew with three 200-plus-pound bluefin tuna.

“Other boats would be trolling around the offshore rigs, looking for fish, when they would see Jason pull up, stop for a few minutes and drive off,” Tally says. “He could tell right away whether or not there were fish in the area. Then they would see him later at the dock weighing, and word eventually got around how this technology made him much more efficient with his time on the water.”

Buck has notched some big paydays on the big-game tournament circuit, including a $1 million payout in last year’s Blue Marlin World Cup, a July Fourth tournament that attracts the world’s finest vessels and crews, all competing to land the biggest blue marlin that day from any location worldwide.

Another Viking 70, Goin’ In Deep, used Furuno omni sonar to help boat the heaviest tuna and heaviest marlin weighed in during the 2017 Mid-Atlantic tournament, earning well more than $1 million in prize money and side calcuttas.

Obviously, an investment of this magnitude makes more sense for guys who fish competitively and chase prize money. But whether or not there’s a pot of gold at the end of the line, the old-fashioned need to keep up with the Joneses is helping drive the sonar arms race.

Advice from a Pro

Commercial fishermen and professional captains have been using sonar for decades, perfecting their interpretation and techniques through countless hours at the helm. For the yacht owner suddenly blessed with these advanced capabilities, however, all this technology can be overwhelming.

Capt. Pat Cavanaugh, of the San Diego charter boat Pacific Dawn, spends half his life on the water and has been running the same Wesmar searchlight sonar since 2003. More often than not, it’s been his voice that I’ve heard crackling over the loudspeaker as I stood by, ready to hook up. Recently I watched as Cavanaugh played “sub hunter” with schools of 200- to 300-pound bluefin tuna, including one group he estimated to be 1,000 feet across. On deck we all waited and watched anxiously for him to gain the position needed to skip our trolled kite baits into the path of the fish. Once we did, the result was pure pandemonium.

When the dust settled we had put four “cow” bluefin of 217, 218, 240 and 293 pounds on the deck. It was an excellent lesson in advanced sonar use.

“Most boaters who are new to sonar just drive to the school of fish and stop,” Cavanaugh says. “You might pick up a few stragglers, but the bulk of it has already moved on. You need to get in position to stop the school and make the fish stick with the boat. Tuna are usually moving fast, so you need to pace them, figure out where they’re heading and get in front of the school.”

When he’s searching for fish offshore, Cavanaugh usually sets his sonar to sweep 180 degrees and 400 to 500 feet ahead of the boat. This shortens the train time and shows him what he needs to see most. “When I get on a stop and we’re hooked up,” he says, “I switch the sonar to 360 degrees so I can track which way the school moves when they leave us.”

Sound also plays a huge part in finding fish with searchlight and sector sonar. The audible tone of the sonar return changes when a target is detected, something to which experienced captains are attuned. “Often, you can hear fish long before you see them — even if they’re out of range,” Cavanaugh says. “Or you could be shooting above or below the main school, so you won’t see them on the display, but you’ll pick up the sound. You turn toward where the beam was when you heard it, and you often find the school.”

Time on the water teaches most skippers how best to set up their sonar for the type of fishing they’re doing, and for the weather and other conditions. For example, when the seas are up, Cavanaugh tilts the beam downward a bit and reduces the range to minimize the effects of sea clutter. Stabilized transducers help with this but can’t fully alleviate the effects of boat movement.

“With the bluefin we’ve had lately, I’m shooting out to about 900 feet in decent weather because these are big targets that will show up at long distances,” he says.

In certain situations, what’s behind the boat might be more important than what lies ahead. Marlin fishermen are often focused on fish coming into their trolling lure spread or rising to their teasers, so scanning behind the vessel can give them a heads-up when something good is about to happen.

Sonar also helps skippers spy beneath weed lines and kelp paddies far in the distance, so they know whether it’s worth stopping or even trolling nearby. And the systems can be useful for inshore and bottom fishing. Tilting the beam downward can provide a long-distance look at reef and structure areas and can be particularly useful in pinpointing schools of gamefish, such as California yellowtail, that often move around as they prowl these structure areas.

“I get a lot of yacht owners and captains asking me, ‘Do I need this?’ ” Tally says. “I tell them, ‘No, you don’t need it. The question is, do you want it?’ Sonar isn’t some magic bullet that is always going to help you catch more fish, but in many situations and fishing conditions it can be an extremely powerful tool to have in your arsenal.”


Training Tips

When it comes to sonar, practice makes perfect. There are no shortcuts: Time on the water and turns of the transducer are the only ways to hone your skills and discern the species, size, movement and behavior of the fish you’re looking at. However, there are some first steps that all new sonar users should take.

Any good installing dealer should offer a commissioning trip and on-board training session for basic operation skills. Make the most of this opportunity by having a plan, asking lots of questions and spending as much time on the water with the dealer as possible.

For learning searchlight and sector sonar, Todd Tally, general manager of Atlantic Marine Electronics, recommends going out to practice on reliable subsurface targets, such as aquaculture pens, oil rigs and fixed navigational markers. This can help you learn how targets appear on the display, and how the display reacts when you move the vessel, steer the beam or change settings. With facilities in New Jersey and Florida offices in Riviera Beach, Bradenton and Destin, AME ( works with boaters throughout the East and Gulf coasts.

Because it continuously broadcasts in all directions, Tally says, omni sonar eliminates much of the guesswork. The technology is easier for new users to learn, and perhaps worth the larger investment for those who can afford it.

Whichever sonar technology and system you choose, one thing is certain: The more you use it, the more you will understand what you’re seeing. And the more you understand what you’re seeing, the more it will help you catch fish.


Furuno USA (360) 834-9300
Koden (631) 996-2690
Wesmar (425) 481-2296



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