Assessing sea turtle movements and connectivity among different areas is pivotal to understanding their biology and implementing efficient conservation actions. In the Adriatic Sea, one of the most important sea turtle foraging areas in the Mediterranean, a total of 311 capture–mark–recapture (CMR) records (mostly bycatch) from 294 loggerhead turtles (Caretta caretta) in the period 1984–2021 were analysed. A general fidelity pattern to Adriatic subareas was indicated by a significantly shorter CMR distance than the potential dispersal distance and by the significantly higher proportion of re-encounters in the same area of release than expected. No seasonal pattern was detected between subareas, and shorter re-encounter distances were observed in turtles released and re-encountered in the same season, suggesting different winter and summer residential areas. Results suggest that turtles frequenting the Adriatic can go anywhere in the Mediterranean basin and may exhibit a wandering behaviour regardless of their size. A substantial connectivity with nesting sites in Greece was observed, confirming with empirical evidence that this is the most important breeding area for turtles foraging in the Adriatic Sea. This study highlights the value of cooperation among different groups and shows a main behavioural pattern of fidelity to neritic foraging grounds.

Identifying coastal tracts suitable for sea turtle reproduction is crucial for sea turtle conservation in a context of fast coastal development and climate change. In contrast to nesting aggregations, diffuse nesting is elusive and assessing nesting levels is challenging. A total of 323 nesting events by the loggerhead sea turtle Caretta caretta have been reported in Sicily, the largest Mediterranean island, in the 1944–2021 period, mostly in the last decade. Specific monitoring efforts are the most likely explanation for such an increase and shows that sea turtle nesting may be underestimated or completely ignored in many areas with scattered nesting. The real nesting level along the 464 km sandy shores of Sicily is still unknown and more research is needed. The observed incubation period was relatively long (57 d) suggesting that a majority of males are produced in Sicily, in contrast to the typical female-biased sex ratio of sea turtles. In a context of climate warming producing sex ratios more skewed towards females, the potential of Sicily as a male-producing area should be further investigated. Other reproductive parameters are provided, such as clutch size and hatching and emergence success. A negative effect of relocation on the latter two was observed.

1. Studying the impact of bycatch on marine megafauna, including sea turtles, is challenging for a variety of technical and biological reasons. The Mediterranean Sea has among the highest levels of turtle bycatch globally, notably of the loggerhead sea turtle (Caretta caretta), and bottom trawling represents a particularly relevant threat.2. Bottom trawlers from a recently discovered neritic foraging area, the Gulf of Manfredonia, reported 1,152 loggerhead turtles incidentally caught in the period 2015-2020. Capture locations were available for 497 turtles. These data were complemented by the distribution of fishing effort obtained by the vessel monitoring system.3. High bycatch rates were observed, leading to more than an estimated 5,600 annual captures and to the death of a minimum of 560 large individuals with high reproductive value. These findings are extremely concerning for the affected population and require immediate action. A strong seasonality of turtle bycatch was observed, with most captures occurring in November-March when fishing effort occurs in shallow waters where turtles concentrate all year round. 4. Therefore, a seasonal approach (e.g. adopting measures only in the high-turtle bycatch season) can be pursued as long as the spatial distribution of fishing effort varies among seasons. However, such a spatio-temporal pattern should be monitored; then, in the case of change, although more difficult to implement, an area-based conservation approach should be pursued. Several recommendations are provided, including the urgent implementation of turtle excluder devices, at least on a seasonal basis.

In sea turtles, somatic growth rates and Age at Sexual Maturity (ASM) are important parameters for investigating population dynamics. Moreover, ASM informs on the time lag needed to observe the effects of past environmental variables, threats and conservation measures acting at nesting beaches on future numbers of clutches or nesting females, that are the most monitored indices. Assessing ASM of mixed populations that share the same foraging areas is difficult, as in the case of the Mediterranean Sea that is frequented by turtles originating from both the Mediterranean and the Atlantic. Here we investigated growth rates of loggerhead sea turtles (Caretta caretta) foraging in the Adriatic Sea, known to be frequented only by individuals of Mediterranean origin. Capture–mark–recapture records of 79 turtles provided growth rates ranging from – 1.1 to 9.6 cm yr−1 which were analyzed through Generalized Additive Models. When integrated with previous data on growth rates in the first years of life, results indicate a non-monotonic growth curve, likely due to an ontogenetic shift from oceanic to neritic areas. Using an integration equation, we estimated mean ASM to be 29.5 or 25.0 year based on mean nester size in Greece (83.4 cm curved carapace length, CCL) or across the Mediterranean (79.7 cm CCL), respectively. Growth rates and size-at-age are similar to the Atlantic population, but Mediterranean turtles mature earlier at a smaller size. The heterogenous growth rates and ASM reported so far in the Mediterranean are probably due, at least in part, to different foraging areas.