It’s midnight: Do you know where your tarpon are?

August 9, 2018
By Marcy Shortuse

It’s midnight. Do you know where your tarpon are? That’s a question that Bonefish & Tarpon Trust and its fearless tarpon taggers are working to answer.
Last month marked Bonefish & Tarpon Trust’s third year of tarpon acoustic tagging, generously sponsored by Maverick Boat Group. Earlier this year, with the help of a generous network of guides and anglers, BTT’s tagging team tagged eight tarpon ranging from 60 to 105 pounds in two days.
A different tarpon tagged two years ago in Pine Island Sound was detected later that year near Cape Canaveral, then wintered in the Everglades, and spent some time in the Florida Keys before returning to Charlotte Harbor earlier this year. Time will tell if the eight tarpon tagged this year will travel as widely, and if they will again return to Charlotte Harbor. Since the tags are active for five years, by the end of the study BTT should have and plenty of information on tarpon travels. BTT has tagged approximately 100 tarpon since inception of this project.
To help detect tarpon in Charlotte Harbor, BTT has placed five acoustic receivers (devices anchored on the bottom that detect the ultrasonic ping from the tags – each tag with a unique ID code) in and near the major passes. When a tarpon enters a pass, the receiver detects the tag and records the date and time of day.
In addition to the receivers in Charlotte Harbor, the team has many more receivers farther south. Plus, Florida Fish and Wildlife Conservation Commission and Mote Marine Laboratory have receivers in Charlotte Harbor and throughout the Gulf coast that will also detect these tarpon.
How does the tagging and tracking process work?
The tagging process involves surgically implanting acoustic transmitters that have a five-year battery life into tarpon after they are caught by anglers and guides. Each transmitter emits a unique ultrasonic acoustic signal approximately every 90 seconds that can be detected by specialized autonomous receivers moored on the seafloor. A tagged fish must be within range of a receiver to be detected; this range varies from 50 to over 1,000 yards depending on environmental conditions, such as water depth and wave action. When detected, the receiver also records the date and time, allowing us to track each individual tarpon for years to come.
In collaboration with guides and anglers, Bonefish and Tarpon Trust receivers have been deployed in tarpon ‘hotspots’ in the Florida Keys, Charlotte Harbor, Apalachicola, Georgia, and South Carolina. Chances are that a few of your favorite tarpon spots likely have a receiver stationed nearby. In addition to the Bonefish & Tarpon Trust sponsored receivers, an extensive collaboration of state agencies and university researchers have deployed over 1,300 receivers across Gulf of Mexico and more than 3,000 receivers along coastal southeastern US as part of their studies on many species of fish. Since these receivers can detect any fish containing an acoustic transmitter, we are able to maintain detection coverage of tagged tarpon well beyond that of BTT’s own receivers. Given the distribution of the receivers, data from this network will not only reveal information about broader movement patterns, but also fill in critical gaps about the inshore ‘spatial ecology’ of tarpon, including smaller individuals in the 30-80 pound range.
How does this information apply to conservation?
It’s obvious that the complex movements of tarpon here in Charlotte Harbor and beyond have left many guides and anglers lying awake at night asking themselves questions like: Just how much do tarpon move between various regions of the Gulf of Mexico and Western Atlantic? What proportion of tarpon are ‘residents’ in a small area, versus migrate long distances? Is there a certain size when tarpon begin to migrate, or is there some other trigger? Do tarpon use the same spawning sites each year? Do tarpon return to the same spots each year, or do they explore new locations year by year? Do tarpon return to the same estuary where they were juveniles (like redfish)? How do the declines in water quality that Florida is experiencing impact tarpon movements? To what extent do the Lake Okeechobee discharges into the Caloosahatchee River alter tarpon movements and habitat use? How is the decline of the Florida Everglades and Florida Bay influencing tarpon movements, and has this changed how tarpon migrate to Charlotte Harbor?
These are the questions that we hope the tarpon tracking program helps to answer. The main goal of the project is to better understand tarpon movements and what influences these movements so that we can improve management and conservation. This will help us understand which habitats are most important for conservation, help us in our push for better regulations in other states and other countries, and help better inform water management policies.
With the collaborative help from anglers, guides, and scientists, the information gathered from this study will help to answer some of these pressing questions and will be critical for the proper conservation of this incredible species.
Guides who caught fish for tagging in the Charlotte Harbor area included Capt. Ryan Clase, Capt. Matt Johnson, Capt. Whitney Jones, Capt. Bryant Cole, and Capt. Chris Slattery.
JoEllen Wilson from BTT will be tagging again later this season in Charlotte Harbor. If you are interested in participating, please email her at