Researching the First Years of a Turtle's Life
One of the least understood stages in the life of a sea turtle is the pelagic phase, in which sea turtle hatchlings swim into the open part of the ocean and spend the first years of their life growing and developing. Called the "lost years," this period actually lasts close to a decade in some species.
In a paper published in 2001, FWRI research scientist Blair Witherington wrote about his work observing and capturing neonate loggerheads in their habitat. During 18 trips off the coast of Cape Canaveral, Florida, Witherington followed the western edge of the Gulf Stream. The following is taken directly from his report:
After the initial physical oceanographic measurements were made, timed searches for turtles were conducted by observers on the bow of the research vessel (elevation was approximately 3 m above the surface) as it moved at idle speed (approximately 2.5 knots) through the center of each downwelling line. When a turtle was observed, the observer noted the time of the observation, and the geographic position, species, and behavior of the turtle. Observed turtles fell into four categories:
- Turtles observed but not captured (n = 49). Data from these turtles were used in addition to data from captured turtles to calculate catch-per-unit-effort and species frequency.
- Turtles captured by dip net and released (n = 175). In addition to gathering time, position, and species data, researchers weighed these turtles with a spring scale, measured them for straight-line carapace length (SCL, nuchal to pygal tip), and examined their mouths for the presence of tar.
- Turtles captured with a habitat sampler, lavaged, and released (n = 66). This capture technique was used to collect turtles along with nearby floating material. These turtles were weighed, measured, and examined as in (2) and were given gastric-esophageal lavages to sample recently ingested items.
- Turtles found dead and collected (n = 3). These turtles were weighed, measured, and examined as in (2) and were necropsied so that gut contents could be examined.
All captured turtles were marked with a red grease pencil to identify the turtle should it be recaptured (none were recaptured). Turtles were released into habitat similar to their capture site within 2 hours of their capture.
Sargassum fragments and seagrasses were the most common among the ingested plants, with small, slow-moving animals also in their diets. Post-hatchling loggerheads were found to be low-energy, float-and-wait foragers, living both within and outside downwelling lines. In his paper, Witherington also discusses the amount of tar and plastics found in the turtle's stomachs when the lavages were performed. (See "Tar and Trash Invading Sea Turtle Habitats")
From "Ecology of neonate loggerhead turtles inhabiting lines of downwelling near a Gulf Stream front." B.E. Witherington. Springer-Verlag, 2001.