Monitoring the abundance of green turtles
(Chelonia mydas) is necessary to assess population trends and risks of collapse. This note
presents a study aimed at comparing three techniques for the direct
estimation of green turtle numbers in their foraging habitats (seagrass beds
and reef flats). The experiment was carried out at Mayotte Island, Western
Indian Ocean. The techniques involved were surveys by snorkel, and aerial
surveys using a microlight aircraft and a paramotor. Each technique had
shortcomings and advantages. While each technique provided estimations of
turtle numbers only surveys by snorkel permitted identification of species
and sex, whenever visibility and turtle behaviour permitted. Along
the shorelines, and over foraging areas, the paramotor was found to be most
suitable for direct estimations of turtle numbers. The major advantage of
this technique lied in its capability to obtain a synoptic snapshot of
turtle distribution over foraging areas. Linear surveys from a microlight
aircraft are better suited to monitor foraging areas located further away
from the shore.