COMBINED PHOTO IDENTIFICATION AND FLIPPER TAGGING OF GREEN TURTLES IDENTIFY CONNECTIONS BETWEEN EGYPTIAN RED SEA FEEDING AREAS AND A KEY NESTING AREA IN SAUDI ARABIA

MICOL MONTAGNA^1,#, ABDULRAZAQ ALATAWI², ALI ALGOHANE², SULTAN ALTURKI³, HECTOR BARRIOS-GARRIDO², AGNESE MANCINI^1,4, AHMED AL MANSI⁵, RICARDO O. RAMALHO², ABDALLAH RABIA TAHER¹, AHMED AL ZAHRANI³, MAJA ZAMENCKA¹ & NICOLAS PILCHER³ 

¹TurtleWatch Egypt 2.0, Marsa Alam, Egypt

²King Abdullah University for Science and Technology Beacon Development, Thuwal, Saudi Arabia

³National Center for Wildlife, Riyadh, Saudi Arabia

⁴Grupo Tortuguero de las Californias AC, La Paz, Mexico

⁵National Center for Vegetation Cover, Riyadh, Saudi Arabia

^#montagna.micol@gmail.com

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TurtleWatch Egypt 2.0 (TWE) is a citizen-science project based in Egypt that aims to identify individual green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles in order to provide information on marine turtle distribution, residence patterns, home range, abundance, and trends (https://turtlewatchegypt.net/). The project relies on facial pictures taken by trained professional and recreational divers at popular diving and snorkelling sites along the Egyptian Red Sea coast. 

Data from TWE have been used to enhance knowledge of marine turtles in the Egyptian Red Sea, including confirming the presence of species that had not been observed in a long time, providing information on species abundance and distribution, identifying important areas for marine turtles (Mancini & Elsadek, 2019), and following the health status and recovery of injured individuals over time (TWE, unpubl.). In 2017, TWE data were used to establish a connection between green turtles feeding grounds along the Egyptian Red Sea coast and the Saudi Arabian nesting area at Ras Baridi (Montagna et al., 2017).

The TWE complete photo identification protocol consists of at least two pictures, one of the left and one of the right facial profiles of the turtle (Reisser et al., 2008; Jean et al., 2010). Other pictures that can complement the profile include images of the entire carapace, images of characteristics unique to the individual (e.g., missing flippers, scars, fibropapillomas, malformations of the carapace). Turtles with only partial profile pictures (i.e. not having images for both the left and right sides of their faces) remain unnamed until a complete photo identification profile is compiled. Once the profile is completed, the individual is attributed a name which is used as unique identifier. In order to identify re-sightings, pictures are matched against the existing TWE catalogue complete and incomplete profiles. The matching process first compares the profiles obtained from the same site and subsequently from other sites. Depending on the site and the number of profiles, TWE use a combination of manual and automatic recognition techniques (Crall et al., 2013; HotSpotter, https://github.com/Erotemic/hotspotter).

In January 2023, a female green turtle was photographed at Marsa Tondoba (Marsa Alam area, Southern Egypt, 24.96016° N; 34.93841° E) at a depth of 4m, while feeding on seagrass. The same turtle was observed again in February 2023, in the same area, also while feeding. Both encounters resulted in complete photo-identification profiles of the turtle, which was subsequently named ‘Milka’. 

The pictures showed that the turtle carried tag RS0700 on the right front flipper. After contacting sea turtle researchers in the region, it was discovered that the turtle was tagged in August 2022 by a team from Beacon Department at King Abdullah University of Science and Technology (KAUST) after nesting at Ras Baridi, Saudi Arabia (24.25404° N; 37.57266° E). The complete profile allowed us to trace Milka to November 2020, when only a partial identification was completed. Milka was observed again in 2023, at the same site and three times since then (Figure 1; Table 1).

Figure 1. Milka’s photo identification pictures from all sightings.

Table 1. Chronogram and details of sightings of female green turtle Milka. The GPS coordinates correspond to the general site and do not describe the exact position of the turtle. 

This is the second time that an adult female green turtle tagged in Saudi Arabia has been observed feeding in a site along the Egyptian Red Sea coast: in October 2016 a green turtle was observed feeding in Marsa Abu Dabbab, north of Marsa Alam, with a tag from Ras Baridi (Montagna et al., 2017). After corresponding with researchers working in Saudi Arabia, it was determined that this turtle had been tagged at the same nesting site (Ras Baridi) one month earlier in September 2016 (NCW & NCVC Teams, pers. comm.). Since then, the turtle, named ‘Aussie’, has been observed 30 times, between 2016 and 2023 (Figure 2; Table 2), moving from Marsa Abu Dabbab and Hermes (Figure 3).

Figure 2. Aussie’s photo identification pictures from some sightings.

Table 2. Chronogram and details of sightings of female green turtle Aussie. The GPS coordinates correspond to the general site and do not describe the exact position of the turtle .

Recent satellite tagging studies confirmed that adult female green turtles use nesting and feeding grounds in multiple countries along both Red Sea coasts (Egypt, Eritrea, Saudi Arabia, Sudan), with transits across the Red Sea during their post-nesting migrations (Attum et al., 2014; Al-Mansi et al., 2021), while inter-nesting movements seem restricted to areas closer to the nesting sites (Shimada et al., 2021).

Figure 3. Map of sites where green turtles Aussie (square) and Milka (triangle) have been observed in the context of (a) the entire Indian Ocean basin; (b) the Red Sea; and (c) between 2016 and 2023.

Recent satellite tagging studies confirmed that adult female green turtles use nesting and feeding grounds in multiple countries along both Red Sea coasts (Egypt, Eritrea, Saudi Arabia, Sudan), with transits across the Red Sea during their post-nesting migrations (Attum et al., 2014; Al-Mansi et al., 2021), while inter-nesting movements seem restricted to areas closer to the nesting sites (Shimada et al., 2021).

Photo identification, flipper tagging, and citizen science are powerful and relatively low-cost tools that can contribute substantially to monitor movements of marine turtles, especially in feeding grounds (Montagna et al., 2017; Williams et al., 2017; Benezech et al., 2022). While these tools alone cannot provide a comprehensive or complete understanding of the turtles’ movements and behaviour as do satellite tags, they can still provide important information and foster collaboration among different projects in different countries (Barrios-Garrido et al., 2020).

Further research is needed to better understand habitat use and migratory corridors taken by both adult male and female turtles, as well as hatchling dispersion from nesting grounds, and this can be enabled with a combination of satellite tagging, photo-identification, flipper tagging, and continued collaboration among countries and projects. Engaging citizen scientists, people from coastal communities, fishers, and local authorities from both sides of the Red Sea would also help build support for marine conservation initiatives aimed at protecting not only marine megafauna but also important habitats.

ACKNOWLEDGEMENTS

The authors would like to thank Fourgive (https://www.fourgive.org/) for their generous economic and logistic support. Special thanks to Dr. Mahmoud Hanafy for his continuous guidance and advice throughout the research process. The authors would like to acknowledge the contributions of all dive centres, divers, and snorkelers who supported the project and shared their sightings. Furthermore, we are very grateful to volunteers Miriam Tercon, Marika Lysgaard Cebula, Kaja Barańska and Armin Halicki who contributed time and effort to this project.  Authors are particularly grateful to Baa Foundation and Extreme E for their long-term support to the Ras Baridi Turtle Conservation Initiative lead by KAUST Beacon Department. Finally, the authors want to express their deep gratitude to the following divers and snorkelers who generously provided their photos of Aussie: Wout and Gerry Van Koot, Jan Goossens, Mariska Van Der Paauw, Didier Orange, Rico Mols, and Ruud Van Den Berg.

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