A new scientific publication by Dimitris Margaritoulis and Alan F. Rees, members of the ARCHELON Scientific Committee, highlights the important marine areas they use for feeding and wintering in the Mediterranean. The study was based on more than 40 years of data from ARCHELON’s tagging program in the three largest nesting areas in Greece: Zakynthos, Kyparissia Bay and Rethymno.

How do we tag the sea turtles?

Every summer, during the nesting season, ARCHELON teams patrol the beaches at night and record the turtles that come ashore to lay their eggs. A small metal tag with a unique number is placed on the turtles that are located. This tag number acts as the turtle's ID and allows researchers to identify the same individual if it is found again, even many years later or in another area of the Mediterranean.

From 1982 to 2024, a total of 6,909 different turtles were tagged in this way, while 254 of them were found again at distances greater than 150 kilometers from their nesting area! Many turtles traveled impressive distances after breeding. More than half of the turtles (53.5%) were found at least 800 kilometers away from the areas they were tagged, while almost a third of them (30.3%) were found 1,000+ kilometers away!

Unfortunately, of the 254 turtles found, most were already dead (61.7%). Although the loss of these adult breeding turtles is particularly significant as these individuals are essential for the maintenance of populations, the identification of the dead animals provides very important information about their feeding areas.

Where do turtles go after nesting?

The data showed that after completing their nesting, turtles can cover long distances, from the Balearic Islands in the western Mediterranean to the coast of Israel in the eastern Mediterranean. However, most of the records were concentrated in four main marine areas: the Adriatic Sea (39.4%), the Tunisian Plateau (Gulf of Gabès) (23.2%), the Aegean Sea (18.9%) and the Ionian Sea (12.2%). These areas are characterized by a rich food base and appear to be important feeding and wintering habitats for Greek loggerheads.

It is also striking that turtles from different nesting beaches prefer different feeding areas. Specifically, turtles from Zakynthos (red dots on the map) and Kyparissia Bay (green dots on the map) were recorded mainly in the Adriatic Sea and Tunisia. On the contrary, turtles from Rethymno, Crete (black dots on the map) prefer the Aegean and the Levantine Sea.

The Value of Long-Term Monitoring

The ARCHELON tagging program is the longest-running program of its kind in the Mediterranean. The 43 years of data reveal movement patterns that would not have been possible to see through individual observations. The most important conclusion is that protecting the Loggerhead is not limited to nesting beaches. It requires preserving the marine areas where the turtles spend a large part of their lives, namely their wintering and feeding grounds.

Important aggregation areas for turtles in Greece were identified in:

• the northern Aegean (Natura sites GR1150014, GR1130009),
• the Amvrakikos Gulf (Natura site GR2110004),
• the island of Lesvos (Natura sites GR4110007, GR4110005),
• the Corinthian Gulf (Natura site GR2530007), and even
• the Saronic Gulf.

Read the entire scientific publication here