Sea turtles spend most of their life cycle in foraging grounds. Nevertheless, given the logistical ease, bulk of studies are carried out in nesting grounds. One strategy to gather information in foraging grounds is the use of cost-effective and non-invasive techniques that allow public participation. The present study aimed to use photographic-identification to investigate the spatio-temporal distribution of Chelonia mydas and Eretmochelys imbricata. Furthermore, we describe the occurrence of fibropapillomatosis. This work was carried out at subtropical rocky reefs of the Brazilian coast in Arraial do Cabo (22°57’S, 42°01’W), within a sustainable conservation unit. The images were obtained through social media screening, citizen science and intentional capture. A total of 641 photos (between 2006 and 2021) and 19 diving forms (between November 2019 and March 2020) were obtained. All diving forms presented at least one turtle. The photo-id identified 174 individuals of C. mydas, with 45 resighted individuals. E. imbricata had 32 individuals identified, and 7 individuals resighted. The median interval between the first and last individual sighting was 1.7 years for C. mydas and 2.4 years for E. imbricata. Fibropapillomatosis was only observed in C. mydas, with a prevalence of 13.99% and regression in 2 individuals (10.00%). The results indicated Arraial do Cabo as an important development area for sea turtles with resident individuals showing fidelity for at least 6 years. As the region accumulates anthropogenic impacts, it is critical to propose significant management measures to protect sea turtles from continuous and synergistic impacts, mainly on resident individuals.

Sea turtles spend most of their life cycle in foraging grounds. Research in developmental habitats is crucial to understanding individual dynamics and to support conservation strategies. One approach to gather information in foraging grounds is the use of cost-effective and non-invasive techniques that allow public participation. The present study aimed to use photographic-identification (photo-ID) to investigate the spatio-temporal distribution of Chelonia mydas and Eretmochelys imbricata . Furthermore, we describe fibropapillomatosis occurrence. This work was carried out at subtropical rocky reefs of the Brazilian coast in Arraial do Cabo (22°57ʹS, 42°01ʹW), within a sustainable conservation unit. A total of 641 images were obtained through social media screening (n = 447), citizen science (n = 168), or intentional capture (n = 26) dated between 2006 and 2021. Additionally, 19 diving forms (between 2019 and 2021) were received from citizen scientists. All diving forms presented at least one turtle. Photo-ID identified 174 individuals of C. mydas , with 45 being resighted, while E. imbricata had 32 individuals, with 7 individuals resighted. The median interval between the first and last individual sighting was 1.7 years for C. mydas and 2.4 years for E. imbricata . Fibropapillomatosis was only observed in C. mydas , with a prevalence of 13.99% (20 of 143 individuals) and regression in 2 individuals (10.00%). Our results indicated that Arraial do Cabo is an important development area with individuals residing for at least 6 years. This study demonstrated that social media, along with photo-ID, can be useful to provide sea turtle estimates in a foraging ground using a non-invasive, low-cost method. Supplementary Information The online version contains supplementary material available at 10.1007/s00227-023-04226-z.