Loggerhead turtles (Caretta caretta) start reproducing when their shells measure more than 80 centimetres, which occurs when they are around 15 years old. The tagged animals had shells of between 33 and 70 centimetres in length, so none of them is yet reproductive age and they are still at the phase of migrations and pelagic life.

The measures adopted in the next few years to protect sea turtles could be vital for the survival of this species. In the last six years, the number of reproductive female loggerhead turtles (Caretta caretta) that have returned to the laying beaches of Florida (United States) has dropped to less than half. And it is these American populations that represent almost 40% of the world sea turtle population.

The loggerhead turtle (Caretta caretta) is the most commom species in European waters, but it is also the one that is most frequently caught by accident. Every year around 40,000 turtles are caught on the hooks of the Mediterranean fleet. For this reason, Oceana is combining this tagging work with collaboration on a project on the Spanish Institute of Oceanography with the fishermen of Carboneras (Almeria) to improve the selectivity of this fishery. The tags affixed to twenty sub-adult turtles will continue to provide information for approximately one year.

Both in the Balearic Islands and the Canary Islands, the Oceana scientists took tissue samples and attached an identification chip to each turtle. After the samples were taken, a satellite transmitter was affixed to the shell of each turtle which would enable their migratory habits, behaviour and other relevant data to be recorded with the aim of proposing management plans for their protection. Every time a turtle comes up to the surface to breathe, the satellite tag emits a signal that is transmitted to Oceana's headquarters, where all the data is stored ready for study.

Many of these turtles originate from the laying beaches of the United States and the Caribbean, although some may have been born in the Easter Mediterranean, especially Greece, Cyprus and Turkey.

It is known that a large number of sea turtles, after leaving the nest in which they were born, set off on a long transatlantic migration that takes them to the waters of the western Mediterranean. They then start their return journey using the Gulf Stream until returning once again to their laying beaches, having completed a round trip of more than 10,000 miles. But much of the biology of these animals is still unknown, such as where they spend a large part of the year, especially in their sub-adult stage and during the winter season.

In previous experiments, tracking turtles by satellite tags has allowed some light to be shed on their habits. We now know that the turtles spend part of their life in Atlantic waters and part in the Mediterranean, and that adult females can lay their eggs on different beaches throughout the same year.