Sea Turtle Tagging

By Allen Foley

In late June of this year, FWRI sea turtle researchers and their NOAA collaborators captured, tagged, and released 105 sea turtles from southwestern Florida Bay. This effort was part of a long-term study of sea turtles in Florida Bay that began in 1990.

These turtles are captured using two, 21’ Carolina Skiffs (each with a 2-person, seven-foot tower) that slowly motor through different areas searching for sea turtles. When a turtle is spotted, the boat is brought up behind it and a snorkeler dives in to catch the turtle and bring it to the surface. The turtle is then brought into the boat for study. The usual work-up involves weighing, measuring, and tagging each animal. A small sample of blood is also taken to determine gender (usually not externally detectable) and genetic identity (to see from which nesting rookery a turtle is from). Notes are made regarding any injuries or signs of disease and the turtle is then released.

The study focuses primarily on the loggerhead and green turtle, but also includes data collected on Kemp’s ridleys and hawksbills. About 1,200 sea turtles have been tagged by this project over the last 28 years and many individuals have been captured several times over time-spans as long as twenty years. In addition to documenting the sea turtle species and life stages that are present in this area, the data collected during this work allow researchers to monitor relative abundance, measure growth, determine sex ratios, identify the proportion of individuals from various nesting rookeries, monitor health status, discern movements, and document residency.

One of the health concerns is the occurrence, effect, and spread of fibropapillomatosis. This can be a severely debilitating and sometimes fatal disease that has already become widespread among green turtles, including those in Florida Bay. It is rare in other species of sea turtles but the Florida Bay study has documented an unusually high percent occurrence of fibropapillomatosis among loggerheads (about 10%). Long-term monitoring of individual loggerheads via recaptures allows researchers to document the progression and effects of this disease in loggerheads.

The Florida Bay study is the only long-term sea turtle study in Florida that regularly includes captures of adult male and female loggerheads on resident foraging grounds. That access allows researchers to study some lesser-known aspects of loggerhead behavior such as the reproductive behavior of male loggerheads and the movements of female loggerheads from the foraging ground to the nesting beach. Satellite telemetry has been used to track the movements of reproductively active male and female loggerheads from Florida Bay during the breeding season. This work led to the discovery of a likely breeding area just offshore of southeast Florida where male loggerheads wait to intercept female loggerheads moving from their foraging grounds to nesting beaches along the east coast of Florida.