Sea turtles are long-lived wide-ranging animals undertaking long-distance breeding migrations showing fidelity to both foraging and breeding sites. This fidelity has led to population structuring with regional management units defined for globally distributed species. Loggerhead sea turtles (Caretta caretta) have established such a management unit in the Mediterranean, with the greatest number of turtles breeding in Greece. Kyparissia Bay, Greece, has been identified as the location with largest nesting aggregation of loggerhead turtles in the Mediterranean. Determining where this aggregation of turtle migrates to outside the breeding season is important for its continued conservation. Long-distance flipper tag recaptures have identified certain high use areas for these turtles but lack route data and certainty that recaptured turtles are resident in the area of capture. Satellite tracking has been used to validate such tag return data and generate insights into turtle migrations patterns and their relationship with phenological and fecundity metrics. Here we recorded turtles' curved carapace lengths as a metric for general body size and deployed Argos satellite transmitters on 11 adult loggerhead sea turtles (8 females, 3 males) during their breeding period in Kyparissia Bay, to examine the implications of their selected migratory routes and foraging strategies. Average carapace length (± SD) was 82.0 cm (± 4.6 cm) for the 8 female turtles and 86.0 cm (± 5.5 cm) for the 3 males. Turtles were tracked for an average of 326.9 days. End points for the tracked turtles were grouped into four distinct regions The Aegean Sea was the end point for 3 turtles, and the Adriatic Sea was the end point for another 3 turtles with one turtle spending an extended period in the northern Ionian. The northern Ionian Sea was the end point for a further 3 turtles and the Tunisian plateau was the end point for final 2 turtles. Six turtles migrated to restricted area foraging sites, 1 turtle remained nomadic for the entirety of its tracking duration, 2 turtles were semi-nomadic incorporating both restricted area foraging and large-scale movements during their tracking period, and the tracks of the final 2 turtles ceased before their behaviour type could be determined, but sedentary behaviour type was inferred. Notably the one turtle that remained nomadic was 6 cm shorter than the next shortest turtles, suggesting carry-over effects of the nomadic life-history. The turtles generally moved to locations that had been identified by flipper tag recaptures, however the tracking identified routes taken to get there, which were often highly convoluted. These foraging sites, also identified through other tracking studies of loggerhead turtles nesting elsewhere in Greece and from Cyprus, were often sites of high fishing activity and cause for concern for turtles present there. Given that up to around 2,000 turtles may nest in Kyparissia Bay during a single summer, we conclude that a larger number of turtles, over multiple years, should be tracked to obtain a more robust assessment of post-breeding migrations, foraging strategy adoption and their carryover effects, which can then be used to better inform conservation and management actions.
Rees et al. (Wed,) studied this question.