15 minute read
The Future of Tarpon
BY MONTE BURKE
New insights from the Tarpon Isotope Study and the Tarpon Acoustic Tagging Project will inform conservation on a regional scale as the mysteries of tarpon migration are revealed.
After baseball great Ted Williams retired from his Hall of Fame career in 1960, his life became subsumed with another game: fishing, mainly for what he deemed “the big three”—Atlantic salmon, bonefish and tarpon. The latter fish became his abiding obsession. From his house in Islamorada, Florida, he fished for tarpon almost daily during the season. He preferred to go out by himself, but would occasionally hire either Jimmie Albright or Jack Brothers or George Hommell to guide him. He helped found the Gold Cup in 1964 and won the event the following year and again in 1967.
Sometime in the late 1970s, Williams got wind of what was happening in Homosassa, Florida, where thousands of giant tarpon arrived every May, and world records were being broken nearly every year. One season, he and the late Islamorada guide, Gary Ellis, decided to travel up there to try their hand. Williams was immediately smitten with the place and its fishing. In an attempt to get in sync with the species and to try to gain any edge he could, Williams demanded that he and Ellis “only eat what the g*ddamn tarpon are eating” in Homosassa Bay, which he figured was sea trout, mullet, crabs and shrimp. So they did. Ellis would later report that he couldn’t really tell if they fished any better because of their diet, “but it was worth a try.”
Williams was honed in on the forage from a strictly angling point of view, but he was approaching something that’s vitally important to the species. Tarpon are what they eat, of course. But they are also where they eat.
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In the 1960s, commercial crabbing was the biggest industry in the town of Homosassa. Blue crabs were everywhere—mating in the area’s four main freshwater rivers and floating the ocean currents in Homosassa Bay—plentiful to the point of absurdity. Guides Steve Huff and Dale Perez, who worked in Homosassa in the late 1970s and early 1980s, say that the crabs would attach themselves to the trim tabs on the back of their skiffs and would try to grab hold of their push poles, their pincers futilely clacking against the graphite.
The tarpon that came to Homosassa every May during those years feasted on those crabs. “Every day you’d see the crabs swimming all over the surface of the water and the tarpon busting on them,” says Ronnie Richards, a longtime Homosassa guide. Huff says that nearly every tarpon landed back then “had crabs coming out of it, from both ends.”
The sheer abundance of the nutrient- and oil-rich crabs likely attracted those Homosassa tarpon to the area in the first place and helped them attain their stupendous sizes (the largest fly-caught tarpon in the International Game Fish Association’s world record book all come from Homosassa).
And it’s likely that the sudden disappearance of those blue crabs put an end to those glorious years in Homosassa.
Citrus County (where Homosassa is located) and Hernando County (which borders much of Homosassa Bay south of Citrus County) were, for a few decades following the 1970s, two of the fastest-growing counties in the United States, booming with dozens of retirement communities and the construction of more than 30 new golf courses. The one thing all of those new developments and golf courses have in common is the need for significant amounts of fresh water. That fresh water comes from a portion of the upper Floridan aquifer, which lies beneath Citrus and Hernando Counties and feeds the area’s springs.
By the early 2000s, Hernando County alone was using fifty million gallons of water a day. Home sites, agriculture and some residual mining pumped out a lot of that water. So did the golf courses, which used something like 370,000 gallons per course every day of the year. That water usage, coupled with severe droughts in Florida in 1980 and 1984, served to draw down the aquifer and reduce the flow of the local springs.
Adding insult to that injury, much of the groundwater became polluted with pesticides and other lawn-maintenance chemicals, as well as nitrates from fertilizer, cow dung and leaky septic tanks. Nitrate levels in the region’s four main freshwater rivers increased by a factor of five between the 1960s and 1990s.
Historically, the area’s four main rivers (the Homosassa, Weeki Wachee, Crystal and Chassahowitzka), along with the many adjacent smaller springs—all of which collectively make up what’s known as the Springs Coast—pumped around a billion gallons of fresh water into Homosassa Bay every day. But since 1980, there has been a drastic decline—more than 50 percent—in the amount of fresh water entering the bay. Less fresh water means more salinity in the bay and in the springs, a problem that’s been exacerbated by rising sea levels in recent years.
Less fresh water means less tarpon forage, as well.
The blue crabs of Homosassa Bay, as it turns out, needed freshwater, too. They rely on it for mating. It also regulates the levels of salinity. Too much salinity, and blue crabs experience lower survival rates, slower molting and higher predation mortality.
As the freshwater flow into Homosassa Bay dissipated, so did the number of blue crabs. By 2000, the biomass of blue crabs in the area had dropped to half of what it was in the 1970s. Thus, the Homosassa tarpon no longer had quite the impressive buffet spread they’d become accustomed to. And it is likely no coincidence that when the blue crabs no longer appeared in great numbers, neither did the tarpon. The equation is rather simple: less fresh water means fewer crabs and fewer tarpon.
The Homosassa tarpon fishery crashed. What was once the tarpon capital of the world, though still fishable today, is but a mere shadow of what it once was, a giant loss in the world of angling. Its fall also serves as a warning, some harbinger of things that very well could come for other places, and other species, unless something is done to try to prevent it. And preventing it means actually impacting policy, management and public opinion. This requires not just knowing something is happening, but being able to prove it empirically.
Which is exactly what Bonefish & Tarpon Trust, along with two scientists at the University of Massachusetts Amherst and host of other collaborators, is in the process of doing.
Dr. Lucas Griffin and BTT Research Fellow Dr. Andy Danylchuk, scientists at the University of Massachusetts Amherst, just smile when they talk about their tarpon isotope study, the latest work they have conducted for Bonefish & Tarpon Trust. The reason? “This was a pretty novel project, cutting edge, and we pushed the envelope a bit,” says Danylchuk. “We had a hunch it would work, but there was some risk involved. The ‘a-ha’ moment for us was when we realized, ‘holy sh*t, this is working.’”
So what exactly are isotopes? In layman’s terms, they are atoms of the same element with different masses. And isotopes of tarpon—measured in a fin clipping —can tell us not only what a tarpon has eaten, but where it was eating. Both are important.
The isotope project was a companion study to a BTT-funded acoustic telemetry study done by Griffin and Danylchuk that tracked the movements of adult tarpon. Before that study, which began in 2016, very little was known about where tarpon migrated and the repeatability of their movements. The movement study revealed that there are two main “contingents,” or groups, of tarpon in the Gulf of Mexico/Florida region. There is one in the western part of the Gulf that migrates east and north, past Texas, to the Louisiana Delta. And there is another contingency in and around Florida that contains within it two subgroups: one that migrates up the eastern shore of Florida past Georgia, South Carolina and North Carolina to roughly Virginia, and one that migrates up the western shore, up the Gulf, also to the Louisiana Delta, which appears to form a natural barrier between it and the western Gulf contingency (though there appears to be at least some crossover between the contingencies there).
Tarpon, it was demonstrated by the study, spend a quarter of the year in the northernmost parts of their range, feeding on forage fish, like menhaden. “What that study told us is that these northern areas are very important to tarpon, that they were foraging areas that sustained them through the migration and the winter,” says Griffin. “But we didn’t have the data to empirically prove why these areas were important.”
So, in 2022, they set out to get it. The idea behind the isotope study was to collect fin clip samples from adult tarpon, which allowed the scientists to see what the tarpon were eating, but also “backtrace” individual fish to their feeding locations. At the same time, they took samples from tarpon prey, including species like crabs, shrimp, pinfish and menhaden. “When we match the two data sets together, we understand what they’re eating and where they’ve been eating, and we can produce a map of their diet and reliance on certain habitats within their range,” says Griffin.
And this is a game-changer when it comes to the conservation and management of the species. “We can now connect the movement of tarpon with their prey base and habitat along their migratory routes,” says Danylchuk. “And we can understand what they’re being exposed to in other parts of their range, which allows for a more holistic approach to conservation and management.”
Starting in 2022, Griffin and Danylchuk began sending fin clip kits to fishing guides and anglers (clipping the dorsal fin of a tarpon is much less impactful than, say, stomach pumping, which is a method of understanding the diet of a fish, but something that’s nearly impossible to do with a tarpon). The kits included scissors, vials and forms for documentation. In all, they sent out kits to 250 guides and anglers, and received more than 850 samples back. The majority came from Florida, of course, but they also received some from Louisiana, Georgia, South Carolina, North Carolina and even Costa Rica and Trinidad. Captain David Mangum, a guide on the Florida Panhandle, was an enthusiastic participant, gathering roughly 50 samples over the two years. “I’m into anything I can do to help tarpon,” he says. “It was a pretty easy process. We’d get ahold of the fish by the boat and I’d have the client lock some hemostats on the dorsal and I’d cut off a piece.”
The samples were sent to one of the collaborators on the project, Dr. Michael Power, at the University of Waterloo in Ontario, Canada, where they were analyzed for carbon, nitrogen and sulfur isotopes. (Another collaborator, Dr. Oliver Shipley at Stony Brook University, provided additional analyses and interpretation.)
The carbon and nitrogen values help determine what type of prey the tarpon are feeding on, and the sulfur values help determine where the tarpon eat, especially in relation to freshwater systems. Taken together, the values “paint a picture,” says Griffin. It was a novel technique for a marine species at this scale, an idea that came from the study of birds, where scientists have used feather clips to discern migration patterns in North America.
The collection of 319 samples from 38 types of prey was done in conjunction with the fin clipping, taken from the areas that tarpon are known to inhabit. Griffin and Danylchuk took those samples, dried them in an oven for 48 hours and then sent them to Dr. Power for analysis, which helped fill out the map of tarpon movement, prey and habitat.
The interconnectedness of it all is the key. It enables scientists, advocacy groups and even anglers to gain a wider understanding of tarpon, that holistic view. Traditionally, conservation and management have focused on the areas where anglers see tarpon, mostly in Florida. This study demonstrates, empirically, that the areas where anglers do not come into contact with tarpon are critical to the overall health and of the species population. Stakeholders are now armed with scientific evidence of the places tarpon eat and inhabit and, thus, where they may face potential threats. That evidence could be used to affect policy in, say, South Carolina, a place where the river plumes are vitally important to tarpon because of the forage there, but also a place where rapid development of the coast and coastal waterways possibly threatens the freshwater flow. “We tend to think of Lake Okeechobee and the Everglades when we talk about fresh water and tarpon,” says Danylchuk. “But the health of freshwater flows in other states in the species’ range is also vital.”
The evidence could also be used to influence policy on prey, like menhaden, an important forage fish for tarpon and many other fish, and a species whose regulation is uneven, at best. “This is a tool for conservation groups, policymakers and anglers. We can’t just focus on the tarpon when it comes to conservation and management,” says Danylchuk. “We need to be advocating for the protection of their prey and their habitat, and include those things in fisheries management. We now have the map drawn of who needs to be at the table for those discussions.”
There are two more initiatives, thus far unfunded, that could truly fill out a tarpon “map.” One has to do with juvenile (1-2 years old) and subadult (up to 10-12 years old) tarpon. These juveniles tend to congregate in places that are most impacted by poor water quality, like the Indian River Lagoon and the estuaries that receive the periodical Lake Okeechobee discharges which are filled with hazardous levels of nitrogen and phosphorous. Griffin and Danylchuk already have many samples of juveniles, and a full analysis of those samples could provide a better idea of how poor water quality is affecting these soon-to-be adult fish.
The second is a large genetic analysis study, which would be done primarily through the state of Florida’s database of more than 10,000 tarpon samples, which have been collected over the last two decades. This analysis would help scientists learn more about population dynamics, and help establish a population baseline for the species, which “is something that is pretty common knowledge for some fish, but not for tarpon,” says Griffin. That baseline is vital for determining the stability of the two tarpon contingencies, and allows for conservation and management efforts to be more focused and more effective. For example, genetic analysis would address the question of whether the regional groups formed by adult migrations translate to genetically different sub-populations, or does the transport of larvae on ocean currents keep genes flowing between these groups? The information on migrations already shows the need for a regional approach, and the isotope findings point to conservation issues that need attention. Genetic analysis would reveal the geographic structure for regional management – should it be one management plan for the entire range of tarpon, or should management focus on the scale of the regional tarpon groups?
In the end, the work that Griffin and Danylchuk and their collaborators have done—and will hopefully continue to do—has given us tools. These tools allow for a greater understanding of tarpon and the protection of a species that’s important both economically and in ways that can’t be measured by money. And these tools also give us a chance to prevent what occurred at Homosassa from ever happening again.
Monte Burke is The New York Times bestselling author of Saban, 4th And Goal and Sowbelly. His latest 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.
