Creatures of Habit

Acoustic telemetry is rewriting the book on what is known about the movements and habitat use of the Silver King, enabling new conservation approaches.

BY MONTE BURKE

Tom Evans, the owner of many fly-fishing world records for tarpon, began fishing in Homosassa, Florida, in 1976 and has pretty much fished it every year since, missing only three years during that time. Because he is a seeker of world records, Evans has been a keen observer of tarpon behavior in Homosassa and, in fact, kept a meticulous logbook full of notes detailing every day he spent on the water there for 24 of those years. Among the most striking revelations from his observations and logbook, particularly in the earlier years, is just how predictable the behavior of the tarpon that migrate through Homosassa was. Every year, the tarpon would show up right around the same date, starting with a slow trickle and eventually becoming a fullon downpour. The fish would remain in the area—laying up, rolling, traveling in strings, forming daisy chains, sometimes heading out into the Gulf of Mexico and then coming back in—for roughly the same amount of days. And then they would leave at around the same date. There was even a single fish—nicknamed “Spooner” for a distinctive chrome spot on one of its gills—that Evans and other anglers and guides saw on the flats of Homosassa Bay for decades. The tarpon that Evans observed seemed to move, from year to year, in a somewhat repeatable fashion, either because of instinct or adaptation.

The other striking revelation of Evans’ observations and logbook is just how precipitous and momentous the collapse of the Homosassa tarpon fishery was, starting sometime around the early 1990s. Though one can certainly still find a decent amount of tarpon there today, the great historical run, when there were thousands and thousands of fish around for much of the month of May, no longer exists, and no one really knows where that body of fish went. Of course, this, too, may suggest some sort of repeatability—that the tarpon, for whatever reason, left Homosassa and then began to “repeat” the new behavior.

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The types of observations that Evans and others made in Homosassa (with the exception of annually spotting an individual fish, like Spooner) are common throughout the inshore portions of the migratory range of tarpon, from Latin America to the Gulf of Mexico and up the southeastern Atlantic coast of the United States. Though anecdotal in nature, they are solid and useful. Guides base their seasons on them. Clients plan their fishing trips around them.

Soon, though, the evidence for the manner in which tarpon move may not be solely anecdotal, thanks to research funded by Bonefish & Tarpon Trust (BTT) and spearheaded by BTT Research Fellow Dr. Andy Danylchuk and Dr. Lucas Griffin of the University of Massachusetts Amherst. Danylchuk and Griffin, along with BTT and a handful of other scientists, have produced a research paper that details a four-year tracking study of 200 adult and juvenile tarpon that demonstrated that, yes, the migratory movement of tarpon is, for the most part, repeatable. The paper has been submitted for scientific review.

Danylchuk and Griffin’s research has some significant implications for tarpon angling—anglers and guides may be able to better understand their quarry. But, more important, it may also help with the conservation of the species and, perhaps, help prevent what happened in Homosassa several decades ago and what, alarmingly, appears to be happening in the Lower Florida Keys right now.

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Tarpon have never been a commercially viable food fish, and because of that, scientific inquiry into the species is seriously lacking. We know much more about the life cycles, spawning routines and general movement of, for instance, tuna, salmon, cod and orange roughy than we do of tarpon. Research funded by BTT on tarpon movement patterns is a big step in gathering more information about the species.

Danylchuk, Griffin and BTT began the ambitious tarpontagging program in 2016. With the help of fishing guides in places like Apalachicola, Tampa, Charlotte Harbor, Indian River Lagoon, Georgia, South Carolina and the Florida Keys, they were able to place acoustic telemetry transmitters in some 200 adult and juvenile tarpon (the biggest tarpon they tagged was 165 pounds; the smallest was 10 pounds). The acoustic tags allowed scientists to track the tarpon for a much longer period (five years) than a satellite tag (a month or two) would, and allowed for more frequent location “pings,” thanks to the various receivers set up in coastal waters. (Danylchuk, Griffin and BTT were able to get shared information from receivers operated by the Florida Fish and Wildlife Conservation Commission and the Georgia Department of Natural Resources, among other entities.) The drawback of the acoustic tags is the range—when the tarpon swim into deeper waters, they are usually unable to be tracked. Still, with the large number of receivers along the coast, a pattern of movement can be ascertained.

In the Florida Keys, the study tracked more than 50 fish. Of that group, 10 were juveniles. This collection of fish exhibited some interesting habits. They migrated to the Keys after the winter, arriving from multiple spots—Miami, Cape Canaveral, Tampa and the Everglades among them. Some of the fish would stay in the Keys for a week or two and then suddenly leave, with the next detection a few days later in Georgia or South Carolina, before heading back to the Keys and migrating north along the coast. One fish they tracked did multiple migrations and then went to the Chesapeake Bay until the early fall before moving south again. “What we found was that these fish traveled incredible distances, more than we ever thought before,” says Griffin.

Tarpon are a major component of Florida’s recreational saltwater fishery, which is worth in excess of $9 billion annually.

Silver Kings

The tagging data demonstrated that the adult tarpon stayed in the Keys between 40 and 60 days on average, and that none of them stayed there year-round. (Some of the juveniles, did, however, appearing to join in some of the migration and then stopping in the middle of it, as if learning how to migrate in increments). According to Griffin, what this suggests is that the Keys are a hub for tarpon, an important area they use as a staging ground before they spawn in deeper water.

But what prompted the tarpon to arrive in the Keys when they did? To get that answer, Griffin cross-referenced the arrival data with lunar cycles, sea-surface temperatures and what’s known as the “photo period,” which is the amount of sunlight during the day.

The entire population of fish arrived in the Keys when the seasurface temperature was between 78 and 80 degrees Fahrenheit in April and then left when the temperature was between 80 and 84 degrees in June. But when Griffin looked at individual fish, he discovered something interesting. “We wanted to see if an individual fish arrived in the first week of April one year, would it do it again the next year and the year after that?” says Griffin. “The answer was ‘yes.’ We saw that individual fish were incredibly repeatable when it came to their arrival,” he says. While the temperature might influence migratory movements, “the photo period at the individual level, and not temperature, is the likely driver of arrivals.” This makes some sense since temperatures fluctuate dramatically and would be harder to time, of course.

So what does this mean for anglers? For one thing, it means that if you fish for tarpon in the Keys around the same time every year, it’s likely that you are fishing over the same body of fish. And that knowledge—and relationship with the fish, really— comes with some stewardship obligations, especially given the importance of the Keys to the tarpon life cycle. “If anglers aren’t careful, they can have a direct impact on a certain body of fish,” says Griffin. Being careful means playing tarpon as quickly as possible. It means moving if sharks are in the area being fished. It means handling all caught tarpon with care.

It also means that habitat—which is under pressure now from water quality issues, dying seagrass and lack of proper freshwater flow in the Everglades—needs the necessary attention. Given the lack of funding or, really, care from government agencies (which assumes that catch-and-release fisheries are regenerative), most of the responsibility for tarpon is placed in the hands of those of us who target them as a sportfish.

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The conclusions from the acoustic telemetry study jibe fairly well with the folks who spend much of their time on the water, in constant contact with these tarpon: the tarpon guides. Scott Collins and Albert Ponzoa, out of Marathon, and Don Gable, out of Key West, all agree that the fish show up in the Keys generally around the same time each year. Weather, though, can be a variable in terms of how they move. “They’ll be there even if it’s cold and blowing 30 miles-an-hour,” says Collins. “They’ll just hunker down then in the channels and not swim the shallower water. But there always comes a time when that big push comes and they start to swim.” Says Ponzoa: “The fish definitely come in about the same time, starting to show up on the outer ridges of the Gulf. When we’ve had three to four days of good weather, we start looking.”

All three guides agree that the population of fish from the Middle Keys to Key Largo seems stable. The tail end of the season has appeared to thin a bit in terms of numbers, according to Collins, but, all in all, the fish and their movement have remained fairly predictable.

All three guides, though, also agree that there is something potentially catastrophic going on with the large population of tarpon that used to swim each year from Key West to roughly Big Pine Key. “There’s a big body of fish missing,” says Ponzoa. “They used to come in on the northern reaches of Big Pine, from Sideboard Bank coming west. That area, all of the channels and basins, used to fill with these tarpon. But we can’t find them anymore.” Says Collins: “Something has majorly changed down there. Key West Harbor is not loading up with fish. The tarpon used to lay up in Seaplane Basin, but they don’t anymore. Something has happened. There’s been a mass exodus.”

Tarpon swimming across a flat scarred by a propeller. The number of Keys flats classified as “severely degraded” due to propeller scarring has increased 90 percent over the past 20 years.

Ian Wilson

Because he’s based in Key West, Gable has been a firsthand, almost daily, witness to the change. “We started to see something about six years ago, small changes to the fishery and its patterns,” he says. “There were fewer fish traveling the traditional migratory routes. Some tarpon started coming in perpendicular to the shore as opposed to swimming parallel to it. And now, they seem to be gone for the most part.” Gable says that, for now, he still has a bit of a tarpon-fishing season each year in his area. But he’s scared it might not last for much longer. “If we continue the rate we’re on, I think we’re going to lose this fishery completely,” he says.

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Tarpon are an ancient species, dating back, in current form, around 50 million years. During their time on earth, they have survived the extreme heat of the early Eocene Epoch, the extreme cold of the Pleistocene’s ice age and a massive die-off of the earth’s large animals that happened 13,000 years ago. They also, as individuals, can live to an old age—radiometric dating indicates that they can live to up to 70 or 80 years. They have proven to be highly adaptable.

They can certainly become habituated to human behavior— the fish that are fed daily by tourists at Robbie’s Restaurant and the fish who appear to purposely stay in the “no-fishing” zone at Bud & Mary’s Marina in Islamorada certainly illustrate that.

It makes some sense that if tarpon can become conditioned to the food and safety that humans provide them, they can also become conditioned to any human-caused sign of danger or discomfort.

Tarpon have also disappeared from certain of their oncefavorite spots in the world. Port Aransas, Texas, was a famous tarpon-fishing destination in the 1930s and 1940s. At the height of its popularity, hundreds of tarpon were caught and killed during every day of the season there. Water quality issues also plagued the area around that same time. By the 1950s, the Port Aransas fishery was no more.

In Homosassa, though the fishery remains, it’s merely a remnant of what it used to be. Killing fish wasn’t the culprit of the decline. But boat traffic (Homosassa exploded in popularity once word got out about its big fish, and 20 boats on the water per day quickly became 100) and environmental degradation (decreased flow and more pollution in the freshwater springs that drained into Homosassa Bay) are the more likely culprits. This was a population of fish that repeated its behavior, perhaps for centuries, and then suddenly stopped, most likely from humanimposed conditions.

The opportunity to sight-fish for tarpon during the annual migration draws anglers from around the world to the Florida Keys.

Silver Kings

The causes of the missing population of fish in the Lower Keys—which Griffin says were part of the impetus for the tracking study—remain a mystery. But, again, most likely, it has something to do with us. Perhaps it’s the dying seabed in Key West Harbor? Or the pollution? Or oil spills? Or maybe it’s simply too much cruise ship, pleasure boat and jet ski traffic in the area? Tarpon migration has everything to do with maximizing “growth, survival and reproductive success” as Griffin writes in his paper. Human interference can get in the way of any or all of those things.

We may never know for sure why tarpon appear to have left the Lower Keys. But what’s become clear from Griffin and BTT’s new work is that humans and tarpon are in this together. And we need to focus increasingly on ways in which we can hold up our end of the bargain.

Monte Burke is The New York Times bestselling author of Saban, 4th And Goal and Sowbelly. His new book, Lords of the Fly: Madness, Obsession, and the Hunt for the World-Record Tarpon, is available now. He is a contributing editor at Forbes and Garden & Gun.