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Bonefish Breakthrough
The discovery of a bonefish pre-spawning aggregation site in the Florida Keys is another hopeful sign of recovery.
By T. Edward Nickens
For hours, the researchers refused to take a drink of water or a bathroom break. On Bonefish & Tarpon Trust’s 23-foot Pathfinder, idling in the weak light of dawn above the offshore reef tract that parallels the Upper Florida Keys, BTT’s Florida Keys Initiative Manager Dr. Ross Boucek, BTT Research Biologist Natasha Viadero, and intern Parker Denton were glued to a sonar screen. The scan showed a glowing red blob under the boat—a school of bonefish that measured 20 feet from top to bottom. “We barely allowed ourselves to breathe,” says Boucek, recalling the intensity of the moment. The team had been following the massive school of pre-spawning bonefish for nearly 12 hours— from sunset the previous day to the yawning dawn of April 15, 2023—and exhaustion was gaining a stranglehold on the excitement of the moment. And summer was coming. This was very likely the last chance the scientists would have for at least six months to try to solve one of the most bewitching mysteries in marine fisheries: Where do the famed bonefish of the Florida Keys spawn?
In an era in which scientists have plumbed nearly every corner of the globe, it seems oddly curious that the reproductive ecology of a fish worth millions of dollars to the economy of South Florida can seem as little-known as the dark side of the moon. Scientists do know that bonefish gather in giant pre-spawning aggregations (PSAs) as they migrate to spawning grounds. BTT researchers have recently identified seven such critical sites in the Bahamas, and one in Belize. But where the Florida Keys fish spawned was an unknown—and a critical piece of data for the conservation of the species.
Now the giant aggregation of bonefish, a species far better known for its habit of feeding in inches-deep water than meandering the ocean depths, headed for deep water yet again. Boucek winced. He’d been on this hunt for nearly two years, and now he was as close as he’d ever been to witnessing Florida bonefish spawning in the wild. He leaned on the boat throttle, and once again, followed the fish.
ON THE HUNT
In September of 2021, BTT kicked off a search that had long been a Holy Grail for flats fisheries advocates: The discovery and documentation of a spawning location of Florida Keys bonefish. In the Bahamas, three of seven PSA sites identified by BTT scientists have been protected as Bahamian national parks. But in the Florida Keys, the specific locations used by PSAs—if they exist at all—has remained a mystery.
The three-year research project—which is still ongoing—involved extensive interviews with fishing guides, and intensive monitoring of tagged bonefish over the last two years. The work had honed in on a short list of possible PSA sites in the Keys, and the subsequent plan to intercept them looked like something that had been war-gamed at the Pentagon.
If acoustic monitoring arrays could alert researchers to the formation of an inshore bonefish aggregation, and if the scientists could catch a bonefish out of the school, and if they could surgically implant it with a continuous pinging tag, and then get to the offshore reef in time, and intercept the school with its tagged fish, and follow the bones day and night using drones and telemetry, they just might be able to identify for the first time one of the spawning locations of Florida Keys bonefish. The “ifs” piled up like seashells on a high-tide line.
Approaching December of 2022, all the assets were in place. Based on earlier findings, the team had shifted acoustic tracking receivers from as far away as Tavernier and Key Biscayne to a 25-square-mile sweet spot off the Upper Keys. BTT’s Pathfinder was outfitted with tracking equipment, fishing rods, and an array of surveillance tags: In addition to standard 13mm bonefish tags, BTT had procured larger 16mm tags powered by a 5-year battery, Acoustic Data Storage Tags capable of recording and transmitting depth-of-dive data, and continuous pinger tags that would allow researchers to follow tagged fish offshore. Under the advice of BTT chair Carl Navarre, BTT invested in a specialized sea buoy outfitted with instrumentation that would text BTT scientists whenever a tagged bonefish passed the buoy. If the Bonefish Buoy pinged, Boucek and his team might have as little as 24 hours to be on site.
Calendars were cleared from January through April of 2023, as the researchers monitored bonefish movements, watching for bonefish to move towards suspected spawning sites. There was activity in late December, but it fizzled out. During January and February, the fish simply didn’t spawn. On March 1, the Bonefish Buoy pinged, and the team launched to intercept an inshore aggregation. Viadero and Denton caught six fish, and deployed a pinger tag in one of the bones. The team followed the fish for three days as it meandered along an offshore reef. Unfortunately, an after-midnight near-miss with a large center console boat sheared the telemetry equipment’s mount off the Pathfinder, which promptly ended that search.
The next potential spawning period in mid-March was weathered out. April loomed, typically considered the end of the bonefish spawning season.
“Thinking back about all of this, it might sound like we were running around like chickens with our heads cut off,” says Boucek. “But every time we went out, we got a little closer, and a little closer.”
In early April, the last month of the spawn, a forecast suggested slick seas and clear skies for a few days. Boucek had a good feeling. He called photographer Ian Wilson and invited him to join the chase as soon as the Bonefish Buoy sounded off. “I knew that could be a mistake,” Boucek laughs, thinking about that decision. “As soon as you line up a photographer, you can bet nothing will happen.”
But overnight on April 2nd, the Bonefish Buoy sent out a text alert. Fish were on the move. Boucek, Viadero, Parker, and Wilson shoved off at sunrise, and raced to intercept the aggregation. Within 45 minutes they had found a massive group of fish. On the bow, Wilson remarked that they just ran over some bonefish, but when Boucek glanced overboard, the fish he saw were too large to be bones. “They must be barracuda,” he replied. He looked again. Fifty feet from the boat was a swirling wall of bonefish.
Wilson slipped over the side of the boat, and was enveloped in the school of bonefish. What had been a “pipe dream,” says Boucek, at the beginning of the year now swirled under the boat.
The team followed the PSA for most of the day. When four bonefish porpoised on the surface, Boucek grabbed a fishing rod. He instantly hooked a bonefish five miles from shore. Where there weren’t supposed to be bonefish.
But still, the actual bonefish spawn eluded the team. In mid April, a minor tropical storm parked over Miami for several days. As soon as the weather broke, the Bonefish Buoy transmitter pinged: Fish were again on the move. It was very likely the season’s last chance.
STALKING THE GHOST
In the wake of Florida’s bonefish population crash in the 1990s, many scientists believed that so many fish were lost that there was no base population left to effectively spawn. Species that synchronously reproduce in large numbers do so in part because of an evolutionary strategy called “predator swamping.” When so many individuals gather at the same place and time, it dampens the effects predators can have on an overall population. It’s a theory tied closely to why sharp-tailed grouse in the West, for example, gather in massive roosting leks. It’s why passenger pigeons nested in communal flocks that numbered in the millions.
And it’s why passenger pigeons are extinct. The flip side of synchronous reproduction is that a population simply won’t attempt to breed if a population falls below a certain threshold. The last wild passenger pigeon was likely not shot. It’s just that the last passenger pigeons likely would never have bred. Twenty bonefish likely don’t go offshore to spawn. Without a large aggregation and its visual impact and swirling, raucous energy, these species simply sit out the dating game.
Which is why Boucek was so stunned by his in-your-face look at the bonefish aggregation uncovered with Wilson. When he and Wilson were overboard, free-diving with the bonefish PSA, Boucek was surrounded by more bonefish that he ever imagined was possible to see at one time. Wilson looked like a rock in a river of bonefish, rushing by a foot from his camera lens. “And the number of 8-pounders and even larger was incredible,” Boucek says. “I’m certain I’ll never see larger bonefish in my life.”
And the size of the aggregation was larger than he expected. It’s difficult to estimate how many fish a sonogram might capture. Comparing the sonagram captures of the Keys PSA to those in the Bahamas, “this one was twice as long and twice as high,” Boucek says. He estimates the school had between 2,000 to 5,000 fish. “To be honest,” he says, “just seeing that massive PSA was mission accomplished for me.”
But there was more to do, more to ask, more to learn. As mid April approached and the weather cleared, he was back on the hunt for bonefish.
When Boucek woke up on the morning of April 13, he had a text message waiting on him from the Bonefish Buoy. He rallied the team, and Boucek, Viadero, and Denton were on the water at noon. By now they had the process dialed in: Find the nearshore fish. Catch and tag. Intercept the school as it moved offshore. They followed fish for the entire afternoon and evening as the school meandered along the offshore reef tract. Boucek was stunned by its size—likely twice the size of the aggregation of a few days earlier. They were so close, but the window for the spawning season was closing quickly. The hours ticked by. “We ran out of energy drinks at 9 p.m.,” Boucek laughs, “so then things really got terrible.”
At 1 a.m., the school rose from 100 feet down back to the surface, and bonefish porpoised in the green and red glow of the boat’s navigation lights. Then the fish dove again, and swam at full speed another two miles and stopped in 200 feet of water. They slowly drifted along the bottom as sonar signatures from large predators circled the school.
By 5:30 a.m., the team had been on high alert for nearly 18 hours, and stars on the eastern horizon began to wink out with the brightening sky. Suddenly the bonefish hit the gas pedal again. At such a depth, tracking with acoustic telemetry becomes difficult. The signals faded and rebounded, time and again. “We all just prayed that we don’t lose them,” Boucek recalls.
The fish stopped again, this time at the 400-foot drop off. On the small manual tracking screen linked to the pinging tags, the school sank deeper and deeper. Two-hundred fifty feet. Three hundred. Fish known for feeding in mere inches of water were now as deep as a football field is long. The school stopped and hovered at about 350 feet deep, rose 100 feet, then went down yet again. Denton hadn’t had as much as a sip of water in hours, and was feeling the shakes. Boucek had “almost peed in my pants four times because I didn’t want to get off the boat’s steering wheel. It came down to this one moment.”
Under the boat, a school of bonefish thousands strong hovered between 350 and 400 feet deep. On the sonar, the glowing orb rose 100 feet, then dove. It rose another 100 feet. And then came an acoustic anomaly. The continuous pinging tags are inserted into the body of a female fish, next to the ovary. On the ocean surface, with the sun hugging the horizon, Boucek and his colleagues watched as a pinging tag sank below the school, and kept on sinking. It settled to the bottom of the sea at 700 feet deep. The bonefish had spawned the tag out—literally ejecting it from its body with its eggs.
Boucek and company had discovered the first spawning aggregation of bonefish ever documented in the Florida Keys.
They were exultant and exhausted, high-fiving on the boat, when a mahi-mahi free jumped, clearing deep dark blue water 30 feet from the boat. “And that’s when it really set in,” Boucek says. “These Florida Keys bonefish spawn in the open ocean.”
NEXT STEPS
The discovery of an Upper Keys bonefish PSA has conservationists and future-minded anglers buzzing. “The fact that these fish went to 400 feet was astonishing to me,” says Captain Rick Ruoff, a BTT board member and guide who has fished the Florida Keys for more than 50 years. “That was a miraculous discovery. It was a spectacular effort by Ross Boucek.”
Jim McDuffie, BTT President and CEO, agrees. “This is a major discovery for the Florida Keys fishery—and one made possible by our incredible staff who spent countless hours, day and night, on the water chasing it,” he says. “It’s further evidence that the local bonefish population has recovered to a place where it can support large spawning aggregations again. And beyond the discovery and its location on a map, our research at the site will help us understand more about where and how Keys bonefish spawn.”
Now, everyone involved knows that the hard work lies ahead: Protecting the area that is so vital to future of bonefish in Florida.
The precise location of the spawning area remains a secret, and may for some time. While it is surprising that the site has remained hidden in plain sight this long, it is located in a region that’s a bit too far for most snorkeling trips, and not in an area frequently targeted by anglers. There is traffic, but even when numbered by the hundreds, bonefish can be tough to spot. While following one school, Boucek watched a skiff run right over part of a PSA in the area. The boat’s occupants never saw the well-camouflaged fish.
Yet the danger remains. It wouldn’t take much to wipe out a significant chunk of the region’s spawning population of bonefish. A gillnetter could sweep up a thousand bonefish by accident. Unscrupulous anglers could flock to the area to target susceptible fish. It’s likely a matter of when, not if, a charter boat figures out the location. The temptation will be strong to turn such a critical aggregation into a targeted fishery.
Thankfully, there are possible templates for conservation action. The discovery and subsequent seasonal closure of the Western Dry Rocks spawning grounds fishery for permit could serve as an example of how to protect critical habitat in a way that actually enhances a fishery. But there is not yet enough known about how tied bonefish may or may not be to this particular region of the Upper Keys offshore reef tract. More study is critical. “Nothing is going to get better on its own,” Ruoff warns. “The more we know about this behavior, the better we can manage and adjust our efforts towards making a better fishery out of what we have left.”
At a time when there seems to be a flood tide of ill news for bonefish—the presence of pharmaceuticals in bonefish populations, increasing habitat loss, the ever-present question of the effects of climate change—the discovery of a primary spawning grounds is a jolt of positivity and possibility. It underscores the resilience of bonefish, and the impacts of conservation work in the past. And it bolsters an argument for continued conservation action.
“The future looks bright for Florida Keys bonefish,” says Boucek. “We have a population of bonefish that is recovering from a drastic decline that began in the 1990s. The number of 18- and 19-inch young bonefish we are seeing in places is incredible. But we have just a few years to make some big moves to keep good things happening. And first up is the need to keep this reservoir of bonefish safe and happy for a very long time.”
An award-winning author and journalist, T. Edward Nickens is editor-at-large of Field & Stream and a contributing editor for Garden & Gun and Audubon magazine.
