Magazine Post: Fads and Flotsam

Fads and Flotsam

The floating debris that fish love

Story by and photos courtesy Bill Boyce

Waking to smooth eastern tropical Pacific seas, the 240-foot super seiner makes its initial 360-degree slow turn, scanning the horizon for birds and splashes before committing to a course to start the day’s search for tuna. It’s been 34 days at sea, and half of the 1,200-ton fish capacity has been caught with lots more to go before this vessel heads back to port. The helicopter is summoned to take its first flight of the day, and I hop in the back seat to help the fish spotter and pilot find a school of fish to “make the day.” The Hughes 500 C model lifts off the pilot house deck, and a cloud-filled sky greets us as we rise to 800 feet. Being in a chopper on a fine morning like this — some 1,000 miles offshore of Costa Rica — is a feeling few will ever experience. 

Chubs and rainbow runners

For 12 years, I was a fish biologist for the Inter-American Tropical Tuna Commission. I worked on commercial super tuna seiners to ascertain multitudes of data on fish populations, density, distribution and range, and associated species pertaining to porpoise concentrations, flotsam aggregations and school fish populations. When you hear the phrase: “it’s not just a job … it’s an adventure” — know that this job was all adventure. 

We’re 45 minutes into a two-hour flight, and the navigator’s voice fills our ears in our headsets. “Seeing bird targets on the highly sensitive bird radar all over the screen … could be a busy day boys.” He then commands us to run 195 degrees on our chopper’s compass because 6.7 miles away is a good bird concentration. We arrive and see the commotion, but it’s just flying fish being chased by a few hundred dorado. We are then told to run 240 degrees for 8 miles to another “bogie.” Approaching this target, the splashes and breezers immediately tell us it’s a porpoise/dolphin school that has found some deep bait, and the yellowfin tuna have helped herd it to the surface where a massive feast is now in progress. Years before, this school would have been encircled with our mile long net, the dolphin released in a backdown procedure and the yellowfin brailed onboard. Not today. After 1991 and the marketing decision of the international tuna canneries to go “dolphin safe” in their harvest techniques, this school of fish is now off limits. 

With 30 minutes left in the flight, we hear the command to come 345 degrees on the compass and head that way for 7.2 miles. Lots of life has been seen this flight, and we are just hoping for something to make the trip worthwhile. At last — eureka! — we found it: a large piece of rope discarded from an ocean-going tanker, and around it is a circle of radiant blue that becomes a large school of dorado as we survey the vicinity. Hundreds of brown sharks surround the area, and a large area of deep “shiners” — which indicates tuna at depth as they flash and turn in an amoeboid shape of pure fish — resides with this flotsam. This find is fair game, and we immediately tell the vessel to head this way. 


Mariners and anglers have marveled for centuries at the amount of oceanic life that associates with floating debris. It can be mats of Sargasso weed collecting in the currents, or kelp paddies that form once the holdfast root system breaks away to become a floating hotel that swings more offshore in each passing tide. Or flotsam, such as we found, can be manmade: a wood pallet, a rope or a submerged boat that still has enough bow flotation to keep it at the surface. Then there’s more natural terrestrial types of flotsam, like trees that have been cut from tropical rain forests or merely uprooted in tropical storms. They make it from river to estuary to open sea, along the way collecting a variety of fish like a pied piper: small bait fish, jacks, dorado, tuna, billfish, sharks. This creates a diverse population of piscatorial assemblage that all use their piece of flotsam as their newly found “spatial orientation.” From it, they launch daily feeding sorties; at night, it becomes a dense commingling congregation. 

Just about anything, manmade or not, that drifts along in the ocean will attract fish. The ones that we design and build are simply called Fish Aggregating Devices or FADs. An amazing study by Dr. Kim Holland, who works out of the Coconut Island Marine Lab in Oahu, Hawaii, uses radio beacons on tagged tunas. The study found small yellowfin and skipjack tunas would leave the FADs in the morning hours and go as far as 15 miles away during the day on “hunting expeditions” before returning to the FAD each night. This shows us the amazing navigation these fish possess and their schooling behavior in using flotsam as a “common ground” fortress from which to live. 


Depending on latitude, longitude, water temps, time of year and moon phase, fish types can vary a lot. In the eastern tropical Pacific latitudes I typically worked — say from the equator to the 15 degree north latitude, and from 20 miles out to 1,500 miles offshore — these warm year-round waters held yellowfin and bigeye tuna, oceanic and black skipjack, frigate tuna, small amberjack, dorado, wahoo, blue marlin, black marlin, silky sharks, Galapagos sharks, oceanic whitetip sharks and a multitude of forage species of pelagic triggerfish, scads, mackerel, triple tail and flying fish. 

As you head farther north in the Pacific off Baja and Southern California, the species diversity is dramatically reduced to yellowfin, skipjack and in some years, albacore tunas, dorado, yellowtail jacks, small mackerel such as Pacific and jack mackerel, sardines, and the occasional blue shark or mako. 

In the Atlantic and Caribbean Sargasso weed lines, the variety is most commonly made up of dorado, wahoo, small amberjacks, triple tail, blackfin, yellowfin, oceanic skipjack and the occasional blue marlin. 

The moon phase can play a role in the concentration of deep meso-pelagic bait species of sardines, anchovies and squid that are more prevalent in the upper pelagic layer during the full moon cycles. From a feeding perspective, these flotsam brethren take great advantage of the lunar cycles.


When it comes to flotsam, it’s not only the size of it, but also the depth in which it floats. In addition, the speed it floats can make the difference in a flotsam that collects fish and one that doesn’t. A larger size can make a larger “shade footprint,” which attracts baitfish hiding from predatory bird attacks. One with lots of branches can entangle trash and plastic when it’s found in a strong tide rip, and these items can help “slow” the drift speed. The slower a flotsam drifts, the easier it is to keep up with if you are a fish associated with it. The best natural flotsam pieces I have seen are trees that have been in the water for months or years and have become so water soaked that they float very low in the water, making them less susceptible to wind-generated locomotion. When they are covered with barnacles and gooseneck barnacle growth, their speed of drift is even more reduced. The deeper a flotsam hangs down in the water column, the more effective it can be for fish attraction. One time in the Gulf of Panama, we found a few Japanese long line buoys adrift together. There was no real attraction there except for the long deep heavy clump of monofilament line that had been inundated with heavy gooseneck barnacle growth for several hundred feet. Over the course of three sets on this flotsam, we caught almost 400 tons of skipjack tuna from it. In this case, the depth of its drift was more a factor in its fish aggregation effectiveness than its size or its shade. 


As commercial tuna fishermen were forced to find other methods of tuna harvest with the “Dolphin Safe” cannery decision, the need to perfect alternative ways to catch marketable fish was immediately thrown into their laps. Knowing the tonnage and year-round tuna fishery in the western tropical Pacific was already well established, commercial tuna fishing efforts in the eastern Pacific quickly adhered to creating the most effective types of flotsam and deploying them in the most productive currents and latitudes for fishing. Plywood sheets, wooden pallets and old pieces of tuna nets were used for FADS. These early commercial FADS were enhanced with a plastic 55-gallon drum attached to several CASAMAR floats that kept them from sinking, then they were drilled with 2-inch holes and filled with dead tuna to keep the baitfish active. Some were further modified by dragging a few 5 gallon buckets to act as inexpensive sea anchors to further slow the drift, dramatically helping the ability of their efforts to attract large quantities of marketable tuna. 

Not long after, governments from around the world started deploying their own FAD buoys and devices. FADS with anchored appendages soon were helping local fishermen find, catch and benefit from the fish found there. These devices would have an anchor, a chain and a floating apparatus to keep the offering in a vertical presentation. When deployed in commercial shipping lanes, the subsurface depth of the flotsam had to be pre-determined so that large ocean freighters wouldn’t take them away in their propellers, or become navigational hazards for smaller craft. These FADS have since become very popular and effective fish collecting tools, and both commercial and sport fishermen have saved many a day in the areas adjacent to their deployment. 


Boobies perch for a rest on a natural flotsam log. 

With the immediate success discovered in the blue marlin offshore fishery off Costa Rica’s Pacific coast, many more subsurface FADS have been set, and the blue marlin fishing they’ve produced is currently second to none in the world. Is it the FADS attracting these marlin — or is it something else? No, as with the case of any other well-established blue marlin fishery, the presence of small tunas in consistent supply is what drives their success. FADS are always attracting the perfect sized bait tunas for these hungry marlin. Typically, black and oceanic skipjack from 2–10 pounds, as well as small yellowfin tuna, have made these FADS their “staging areas.” All flotsam is important to juvenile-sized and early year class tunas, both for aggregation and survival. “Security in numbers” as they say when you’re a small fish in a big ocean. Once these tunas grow to a bigger size, they will leave the comfort and safety of the flotsam and become open water rangers the rest of their lives. Yellowfin will then begin associating with spotted and spinner dolphins, and bigeye tuna and oceanic skipjack will leave the flotsam to form large roving schools that roam the water column in search of any bait species they can find. 


With the active establishment of FADS off the coasts of many nations, we find a larger number of fish are now available for commercial and sport. Fish that historically may have just migrated through these areas now have a reason to stop, feed and stay a while. From this development, many fishermen have increased their catch, and sport fishermen now have instant targets in which to run to for fishing success in what previously might have been a non-productive habitat. What it all boils down to now is the management of not just the fishery but the type of fishing practices — and the rate of harvest a country will allow in its FAD areas. Densely populated areas are obviously more difficult to manage, but with more science collected and more FADS deployed, hopefully we as humans get ahead of this curve and make the best conservation decisions.  

From the Local Experts Perspective

Todd Staley has fished and captained sport fishers in Costa Rican waters for the past 30 years. His knowledge and his respect of the resource and all those who utilize it made him the perfect person to be the Communications Director for FECOP, Federación Costarricense de Pesca, a great organization that works closely together with Costa Rican fisheries personnel to support sustainable management practices for the inshore/offshore fishery. He gave a history of the FAD fishery established off the Pacific Coast of Costa Rica and explained the dynamics between the various user groups. 

The first private FAD deployment by the sport fishing community was in 2012; since then, over 30 have been set in offshore waters ranging from 10 miles to over 100 miles offshore. It did not take long for fish to find and associate with these fish factories, and the news of the incredible marlin fishing found on, near and around them spread like wildfire. With that good news came issues, such as strife within the angling communities — but more specifically with the commercial industry. Sport anglers practice conservation with catch and release management while commercial vessels use every FAD they find to catch and kill their harvest with nets or hook and line techniques. This alone generates animosity that can become heated at times. 

These FADS are designed to perform their duties under the waves and are therefore set to depths below the surface to avoid detection other than by those with knowledge of the numbers. However, once the “numbers” are discovered, many of these FADS have fallen victim to piracy, not only of the fish associated but also with the entire FAD itself. A few of these are rumored to have been pulled out during purse seine operations in that vicinity. 

Some satellite tag studies currently are being conducted by Stanford University, but it’s been too early to extrapolate any definitive data from these tags. Blue marlin tend to be roaming into and out of the FAD areas with nothing clearly pointing to a resident “home” population of billfish being established due to the FADS. Should this phenomenon ever establish, these FADS could have significance as spawning areas, but it’s way too early to assume that is probable. There is no denial that the blue marlin fishing has dramatically been altered for the better with the placement of so many effective FADS offshore.


Get Your Printed Copy Mailed Today


Signing Up Here to Get Your
Exclusive Teacher Access Code!

Signup Form

Code Valid For All 3 Course Types