Investigating the distribution of foraging sites of loggerhead sea turtles, Caretta caretta, in the Mediterranean Sea

A better understanding on the distribution of highly migratory marine megafauna and the potential exposure of their habitats to anthropogenic activities is essential for ensuring the persistence and the protection of such iconic group of species. Here, we aim to deliver a comprehensive view on the distribution of foraging grounds for charismatic representatives of marine megafauna, loggerheads, Caretta caretta, in the Mediterranean Sea, along with an assessment on their exposure to fisheries. First, we compiled a consolidated database with locations of the adult Mediterranean foraging loggerheads extracted from published satellite tracking data. Next, we applied an ensemble distribution modelling approach so as to develop a map of the foraging grounds across the Mediterranean Sea. Finally, we assessed the exposure of the delineated foraging grounds to the cumulative risk due to different types of fisheries. Our findings revealed that the foraging grounds for adult loggerheads were extended over the 9% of the Mediterranean basin. We identified well-established areas in the central Mediterranean Sea, such as the Northern Adriatic Sea and the Gulf of Gabes in Tunisia, but also highlighted sites, at the western part of the basin, for which the current knowledge was restricted. In addition, we found that the exposure of the foraging grounds to fisheries differed across the Mediterranean Sea, with the Adriatic Sea being subjected to the highest level of risk. The developed approach that combined modeling techniques and risk assessment allowed us to reveal critical sites for sea turtles on which conservation actions should focus. 
This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (ΙΚΥ).

• A better understanding on the distribution of highly migratory marine megafauna and the potential exposure of their habitats to anthropogenic activities is essential for their effective protection.
• Here, we deliver a comprehensive view on the distribution of foraging grounds for the representatives of marine megafauna, loggerheads, Caretta caretta, in the Mediterranean Sea, along with an assessment on their exposure to fisheries.
• Using the available published satellite tracking information on the adult Mediterranean foraging loggerheads, we built a series of distribution models to develop a map of the foraging grounds across the basin. We also assessed the exposure of the delineated foraging grounds to the cumulative risk due to different types of fisheries.
• Our findings revealed that the foraging grounds for adult loggerheads extended over the 9% of the Mediterranean Sea. We identified well-established areas in the central Mediterranean Sea but also sites, at the western part, for which the current knowledge was restricted. The exposure of the foraging grounds to fisheries differed across the basin, with the Adriatic Sea being under the highest level of risk.

Introduction
Mediterranean loggerhead sea turtles: ✓ represent a distinct population with specific biogeographical, demographic and genetic characteristics ✓ local studies have been conducted at the basin focusing on foraging period What is the distribution of foraging areas at the basin scale?
To what extent are foraging grounds subjected to risk due to fisheries?

Introduction
Mediterranean loggerhead sea turtles: ✓ fisheries represent a major threat ✓ over 132000 incidents of bycatch have been recorded on a yearly basis ✓ more than 44000 deaths have been estimated per year ➢ The delineation of foraging grounds of adult loggerhead sea turtles in the Mediterranean basin ➢ The assessment of the exposure of these habitats to the cumulative risk due to different types of fisheries 6

Aim
Step 1: • Collection of presence points of foraging sea turtles via literature review ✓ Adult individuals ✓ Spatial data from satellite telemetry ✓ Exclusion of rehabilitated turtles • Georeference and digitization of presence points (n=119) 7

Methods
Step 2: • Determination of current climatic conditions

SSTs from September to March
Step 3: • Development of species distribution models

Bioclimatic variables Presence points
Step 4: • Collation of data on fishing effort for four types of fishing gears:

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• Largest percentage of foraging grounds was located at the Central and Eastern Mediterranean • Known frequented areas such as the Levantine Sea (19.19%) and parts of the Aegean Sea (13.05%) • Limited extent of foraging grounds was found at the Western Mediterranean, at French and Spanish coasts (7.13% of the total foraging area), for which the current knowledge was restricted.
• Foraging grounds for adult loggerheads covered the 9% of the Mediterranean Sea • Well established areas such as the Adriatic sea (24% of the total foraging area) and the Tunisian Plateau (31.75%) • Adriatic sea: a hotspot of risk of interaction with fisheries (73.47% of its extent subjected to high and very high risk) • More than 40% of the foraging grounds were exposed from medium to very high levels of threat, with variations being detected across the Mediterranean Sea

Results and Discussion
• Western Mediterranean: 57.51% of the foraging grounds under high and very high levels of threat, confirmed by large number of capture events in Spanish waters.
• More than half of the foraging area hosted within the Aegean and Ionian Sea exposed from medium to very high levels of risk (54.38% and 51.52% of the foraging area, respectively), with increased frequency of interactions between fishermen and sea turtles to have been observed both in Greece and Turkey • Lower percentages of risk detected at Levantine Sea and Tunisian Plateau/Gulf of Sidra; however, they should be treated with caution due to poor coverage of fisheries data.
➢ The current study provided a profound knowledge on the distribution of key foraging sites for loggerhead sea turtles across the entire Mediterranean basin.
➢ The assessment of the exposure of the foraging grounds to different types of fisheries allowed us to identify critical regions for which potential interventions should be considered ➢ Additional fine-scale assessments should be conducted to provide specific guidelines for an effective protection and conservation of the habitats of loggerhead sea turtles.