Tarpon Satellite Tagging Program
Atlantic tarpon have reigned supreme for more than a century as one of the most sought-after inshore game fish. The popularity of silver kings soared when President Franklin D. Roosevelt battled them in 1937 off Port Aransas, Texas, and the excitement started years earlier via the exploits of Zane Grey, Charles Holder and a host of other legendary anglers in the Florida Keys.
Despite the longstanding interest anglers have exhibited in the species, we’ve only recently begun to learn more about tarpon migrations and spawning areas in the Gulf of Mexico, southeastern U.S. and the Caribbean Sea.
Are Our Tarpon Their Tarpon?
Anglers have long wondered from where big tarpon come and go. Do populations of the species migrate internationally? And why have tarpon populations declined or increased over years in different regions? These questions are fundamental to determining the unit stock appropriate for management that ensures sustainability of the fisheries. Unfortunately but typically, much more is known scientifically about food fish than species far less desirable for human consumption.
Eight years ago, Billy Pate — an IGFA Hall of Fame inductee — asked at a Bonefish & Tarpon Trust board meeting, “Are our tarpon their tarpon?” Billy had observed firsthand the slaughter of large mature tarpon in various Latin American countries by commercial and subsistence fisheries. He surmised that those impacts may have caused the substantial declines of the tarpon fisheries off Port Aransas and more recently at Homosassa, Florida.
Billy’s question stimulated much discussion and resulted in a scientific quest to utilize new technologies and to develop stronger collaborations to learn the secrets of the population dynamics of migrating tarpon.
Since that time, unprecedented collaborations undertaken among scientists and anglers have spawned state-of-the-art techniques. Guided by biologists from the Bonefish & Tarpon Conservation Research Center at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science and by funding sources such as Bonefish & Tarpon Trust (BTT), research doors are opening more and more. Perhaps the most unique innovation: space-age
Pop-Up Archival Transmitting (PAT) tags. They track tarpon migrations and evaluate habitat use along the way. The PATs, which cost $6,000 per unit and utilize satellite technology, are relatively small computerized sampling devices attached to the back of a tarpon via a titanium dart. A PAT contains electronic sensors that every 10 seconds records the fish’s depth, light level, temperature and salinity of surrounding water (Figure 1).
Unlike conventional anchor tags that require the recapture of tagged fish, PATs can be preprogrammed to automatically release from the fish at a specific date and time (usually about six to eight months after deployment). At that moment the tags “pop-up” to the surface and transmit compressed versions of the stored information to a network of orbiting satellites. All the information is forwarded to our computers at the University of Miami’s tarpon conservation research laboratory for detailed analyses. While physical recoveries of deployed PAT tags aren’t necessary, when they can be found via ARGOS locator devices it allows downloading of the entire data archive. A comparison of environmental data allows estimated locations of the tagged fish along their migration routes.
Funds for this tagging research have been provided by anglers and funding partners from organizations principally led by BTT. Other contributors include the Sanctuary Friends Foundation of the Florida Keys, Tarpon Tomorrow, Texas Parks and Wildlife Department, Florida Fish & Wildlife Conservation Commission, Marine Ventures Foundation and the Texas Saltwater-Fisheries Enhancement Association. Others contributing much
time and resources to the effort include: Scott Holt at University of Texas Marine Science Institute, Tad Burke and the Florida Keys Fishing Guides Association, Angel Requejo and the Veracruz Yacht Club, Scott Alford and the Tarpon Tomorrow Texas Pro-Am, Lance “Coon” Schoest in Louisiana, Bruce Ungar and the Stuart Fishing Club, Joe Mercurio and the ProTarpon Tournament Series, Eduardo Perusquia and the Coatzacoalcos Yacht Club, Sport Fishing Magazine and the Trinidad Tarpon Bash.
Through 2008, about 110 PAT tags have been deployed in Florida and the Florida Keys, Louisiana, Mexico, Texas, Alabama, Georgia, the Carolinas, Mexico, Trinidad BWI, and Angola, Africa. The results show that sexually mature tarpon — at least 100 pounds and a 5.5-foot fork length — are the ones that migrate. Tarpon are sexually dimorphic, with the largest being females that may exceed 300 pounds.
Solving the Migratory Puzzle
In the intervening time since Billy Pate’s posit, we’ve learned a great deal about migration and travel patterns of mature tarpon. They frequently travel hundreds to thousands of miles between seasonal spawning and feeding sites. For examples, tarpon tagged in the southern Bay of Campeche, Mexico, in May have reached Louisiana and Mississippi waters by July and August; tarpon tagged in Trinidad have ventured north of Martinique in the Windward Antilles Islands.
Tarpon tagged in south Florida and the Keys in April and May have migrated to Chesapeake Bay and others to the Mississippi River by July and August. Both of the latter groups presumably are searching oil-and-protein rich menhaden stocks to rebuild the gonads after late spring to early summer spawning. This prepares their bodies for the long return migrations ahead (Figure 2), as the various connection points relate to seasonally available, energy-rich food resources.
With the tarpon’s propensity for international travel and long lives (up to 80 years), they’re especially susceptible to even low levels of exploitation. Tarpon migration distances can also be impressive, with surprisingly large distances covered per day (up to 50 miles). Therefore, extractions from the populations in Mexico, the Caribbean or Central America may directly impact U.S. tarpon populations. This downturn in tarpon numbers could have a huge negative U.S. economic impact, the economic impact of that state’s citrus industry. Trinidad, the Dominican Republic and even Cuba share tarpon migrations with U.S. tarpon.
An area of historical importance is Port Aransas. Historical data indicates that tarpon fishing was excellent along that portion of the Texas coast until the early 1960s. While south of the border commercial fishing for tarpon likely was the most insidious culprit for the fishery’s tragic decline, other factors such as water diversions, the shrimp industry and other impacts may have destroyed habitat and impacted juvenile tarpon. Add to that coastal development, the oil trade and commercial over-fishing, and it’s not hard to see how tarpon populations off Port Aransas — and anywhere — can soon be devastated.
Bellwethers of Climate Change?
PAT-tagging has shown that migrating tarpon have an innate desire for water temperatures of 26° C (about 79°F). It’s an almost magical temperature band that tarpon seek, and they suddenly can materialize, almost overnight, in good habitats with that particular water temperature. That figure is also, surprisingly enough, the lower-bound temperature that tropical storm forecasters use to predict hurricane generation. Their temperature preferences might suggest that tarpon may be one of the first and most prominent species to be affected by climate changes.
How tarpon know where and when to locate such specific temperatures is quite another mystery. Undoubtedly it’s a physical signal that dictates when and where to spawn, and what types of food may be available for consumption along their annual migration route. It’s not that temperature provides a specific limit per se, as tarpon can be found in waters as warm as 90°F. They also often make seasonal feeding sorties into very warm waters pursuing oil-rich prey like menhaden, an extremely important food for silver kings. In any case, this temperature has undoubtedly been imprinted into the tarpon’s genetic makeup.
Tarpon exceeding 100 pounds are well-known shallow-water inhabitants, especially in the Florida Keys and Caribbean. PAT tagging has shown that migrating tarpon are deep-water fish too. Tarpon spend a lot of time in waters depths of 30 to 100 feet, and we’ve documented dives over 450 feet. Their deepest dives usually occur at night. Some of the deepest diving tarpon have been documented during migrations north from Mexico, during presumed spawning off Florida, and also fish from Trinidad crossing between islands in the Antilles chain. We think that most deep dives relate to spawning activities, but perhaps it’s instead for safety or a reaction to currents or prey abundance.
Migrating tarpon also seem to follow well-defined deep-water paths. We documented offshore tarpon up to 50 to 100 miles apart rising and diving synchronously in the water column, which may indicate some bizarre natural order to their behaviors. The more information collected, the more questions arise — it’s like a giant, never-ending jigsaw puzzle. Nonetheless, a critical scientific mission is being pursued to ensure sustained regional fisheries for the valuable and powerful silver king.
To become involved in this new and exciting conservation adventure, you can Adopt a Tarpon by picking up the cost of one or more satellite PAT tags and even joining us on an expedition to observe tag deployment. All donations will go directly to the purchase, testing, programming, deployment and recovery of the tags.
Donations involving sponsorships of tags are handled by Bonefish & Tarpon Trust for the Center for Tarpon and Bonefish Conservation Research at the University of Miami. BTT provides the UM Center a dollar-for-dollar match of your donation. All donors receive a handsome commemorative plaque and a letter documenting their tax deductible gift. In addition, participants receive timely updates of research results by visiting our website, reachable through the link below. Just click on Tagging Program.
Contact Dr. Jerry Ault for more information This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Visit Dr. Ault's web page http://bonefishresearch.com