ISTS Symposium43 Program/Agenda

TurtleWatch Egypt (TWE), launched in 2011, is a citizen science initiative dedicated to gathering essential information on endangered marine turtles across foraging grounds in the Egyptian Red Sea, with no data collection conducted at nesting sites. Engaging local communities, tourists, and dive centers, TWE has compiled a 20-year dataset on turtle populations, with sightings dating back to the first photographic report in 2003. In total, 9,562 sightings were logged across multiple locations, corresponding to 1,441 green turtles (Chelonia mydas), 1,371 hawksbills (Eretmochelys imbricata), 4 loggerhead turtles (Caretta caretta), 1 olive-ridley turtle (Lepidochelys olivacea), and one leatherback turtle (Dermochelys coriacea). In 55 cases, the quality of the picture was insufficient to identify the species.

Data collection has involved both TWE team-led surveys and reports from citizen scientists, with contributions from 960 trained ordinary citizens and partnerships with 96 dive centers. TWE’s collection methods included 6,376 reports from citizen scientists and 1,200 team-led surveys, resulting in 3,186 sightings, yielding extensive information on the turtles’ age and sex distributions: 908 juveniles, 886 sub-adults, 636 adult females, and 1,024 adult males. Among the identified turtles, 381 individual green turtles were observed multiple times (2–141 times), and 144 hawksbill turtles were resighted (2–84 times).

Key turtle activity sites, such as Marsa Abu Dabbab (3,031 sightings), Hermes (899 sightings), and Shams Alam (657 sightings), highlight critical habitats where human-turtle interactions are frequent. TWE data on injuries—a significant indicator of human impact—recorded 40 injured turtles across 290 sightings since 2011, with vessel strikes as a major cause, particularly at high-traffic sites like Hermes and Marsa Abu Dabbab.

Resighting data have provided valuable insights into the likely travel distances between sites for individual turtles, although these represent only the minimum distances between locations where they were sighted. For example, two adult female green turtles, "Aussie" and "Milka," undertook significant journeys. Milka traveled a minimum distance of approximately 277 km between Tondoba Bay and the Saudi coast before returning, while Aussie moved an estimated 310 km between Saudi Arabia and foraging grounds in Marsa Abu Dabbab and Hermes. Another notable movement within Egypt included a green turtle’s minimum travel of 94 km between Marsa Mubarak and Marsa Fukera. Hawksbill turtles generally showed shorter movement ranges (0.5–33 km), with two exceptions in the southern Egyptian Red Sea: turtles migrated between Zabargad Island and Sha’ab Maksur and between Daedalus Reef and Wadi Lahmi Azur House Reef, each covering a minimum recorded distance of 89 km.

Beyond ecological research, TWE emphasizes community education and collaboration. Through bilingual workshops and awareness events, TWE has educated over 2,300 participants, including children, boat captains, dive instructors, and tourists. Impact assessments introduced in 2024 show positive outcomes: Turtle Talks and training sessions increased knowledge by 20%, Turtle Trunk educational activities improved understanding by 26%, and 10% of trained boat captains reported enhanced skills in avoiding turtle interactions.

Through long-term monitoring, citizen science, and education, TWE enhances Red Sea turtle conservation, reduces human-turtle conflicts, fosters sustainable tourism, and protects vital habitats.

In-water monitoring of sea turtles can take various approaches, depending on objectives, geographical context, and resources available. As with all monitoring, one of the major challenges is to sustain efforts over long periods of time. Citizen science programs, which rely on public participation, have become an effective approach for collecting scientific data over large areas and extended timeframes. On Reunion Island, a small volcanic island (2512 km2) in the southwest Indian Ocean, sea turtles are not easily accessible due to their distribution on rocky or coral slopes at depths between 10 and 50. Involving divers and marine users in data collection appeared to be the best solution to complement existing knowledge from aerial surveys and to better characterize sea turtle populations. Therefore, since 2007, Kelonia has initiated a citizen science program based on photo-identification to monitor turtles at sea while also raising awareness.

Contributions from divers and snorkelers have led to the collection of 6,480 photographs and the identification of 653 individual green and hawksbill turtles around the island, with a species distribution ratio of approximately 70:30. The data indicated a recent increase in the number of hawksbill turtles expanding their habitat range over time. Most observed individuals are juveniles or subadults, with only 54 adults documented (21 males and 33 females). The longest interval between an initial and final encounter spans 20 years (mean: 3.97 ± 3.78 years) for individuals first observed as juveniles and now as adults. Photo-ID data also reveal strong site fidelity and limited coastal movement over relatively long periods (average range: 1.15 km).

Additionally, citizen contributions help monitor local threats, including boat strikes, bycatch and entanglements in ghost fishing gear. Injured turtles are rehabilitated at Kelonia care center, while photo-ID is used to track wound healing in turtles that remain in the wild. Photo-ID data have also complemented scientific research, improving accuracy. For example, aerial surveys combined with photo-ID have enhanced abundance trend estimates by life stage for both turtle species (see Laforge et al. abstract 199). Furthermore, photo-ID has helped address gaps in satellite tracking data, particularly in very shallow habitats where turtles exhibit modified diving behavior, reducing surface time (see Laforge et al. abstract 198).

Despite challenges inherent such as uneven public participation and unknown effort levels, citizen science provides invaluable data that supplement traditional scientific research. These findings enhance understanding of turtle biology and ecology, inform conservation strategies, and foster greater public awareness.

One of the techniques used to identify and monitor sea turtles is through photographs of the keratinized plates on their heads, which allow for individual identification. The photo-identification technique is already well-established and effective for identifying individuals at a local level without the need for animal capture. In situ studies provide important information on habitat use, behavioral patterns, fidelity to areas, identification of dietary items, ecological interactions with other organisms, threat identification, and they also help identify critical areas for juvenile population maintenance.

This study was conducted at the Cagarras Islands Natural Monument, a no-take marine protected area (MPA) in the metropolitan region of Rio de Janeiro, Brazil. The area is also recognized as a Mission Blue Hope Spot. Data were collected through scuba diving, during which researchers actively searched for sea turtles in the water column and on the seafloor. The dives were concentrated on the Redonda and Comprida islands. When a turtle was sighted, the researchers took photographs of both sides of its head and the entire body. The animals' behaviors are also recorded, including whether they are resting, swimming, feeding, or interacting with other organisms. The identification of the individuals was performed with the aid of the I3S software and visually by comparing images in the database of the sea turtles recorded over the years.

Between September 2020 and June 2024, 125 individuals were identified (62 at Comprida Island and 63 at Redonda Island), with 124 belonging to the species Chelonia mydas and 1 to Eretmochelys imbricata. Fifty-eight individuals displayed residence behavior, meaning they were re-sighted at least once after the first observation, with the highest number of sightings for one individual being 42. The most extended stay was 45 months for a C. mydas first sighted on September 12, 2020, and last seen on June 13, 2024, totaling seven sightings. No resident individual from Comprida Island was recorded on Redonda Island, and vice-versa, showing high site fidelity. The C. mydas turtles, during their active period, were mainly observed at depths shallower than 10 meters, with feeding areas concentrated on rocks closer to the surface (up to 5 m deep), where red algae and filamentous green algae are abundant; these being the preferred food items. They were also commonly observed feeding on gelatinous organisms. The presence of fishing gear and anthropogenic debris on the islands were the most significant threats identified to the sea turtles. Despite the ban on extractive activities within 10 meters of the islands' rocky shores and on using fishing nets within 200 meters, ghost fishing caused by lines, hooks, and nets still frequently occurs in the MPA limits and surroundings. Only two individuals were observed with fibropapillomatosis, which may indicate a healthy environment despite the proximity to Guanabara Bay, a polluted area. This study identified that these islands, close to a large metropolis, represent a relevant feeding and developmental area for juvenile green sea turtles, highlighting the importance of establishing and strengthening marine protected areas for sea turtles conservation efforts.

Sea turtles spend most of their lives underwater, where they typically feed, breed, and rest – only periodically returning to the surface to breathe. Their ability to dive several hundred meters deep has garnered attention for their physiological adaptations, promoting research aimed to quantifying the maximum depth and duration of dives across sea turtle species. However, much less is known about the diving behavior of sea turtles in shallow waters (< 5 m depth), which are commonly used by juvenile green turtles (Chelonia mydas) throughout the Caribbean. To address this research gap, we aimed to (1) characterize the diving behavior of juvenile green turtles in shallow-water habitats in The Bahamas, and (2) assess how dive depth, activity patterns, surface interval duration, and water temperature may influence dive duration. We deployed 58 animal-borne cameras equipped with time-depth recorders on green turtles (Chelonia mydas) ranging from 32.6 to 63.7 cm Straight Carapace Length. To account for multiple dives per individual, we used a mixed modeling approach within the Bayesian framework. Overall, we recorded 174.9 h of footage with a mean duration of 180 min ± 17 SD. Turtles exhibited notably short mean dive durations (66.43 s ± 75.85 SD) with a mean dive depth of 0.99 m ± 0.79 SD, compared to longer dive durations observed in other studies in deeper waters (e.g., Rice and Balazs, 2008; green turtles with mean dive durations of 38.2 min and mean dive depth of 26 m). Models revealed that maximum dive depth, surface duration before each dive, and mean water temperature had a statistically significant positive relation with dive duration. In addition, active dives (i.e., a combination of swimming, socializing, digging, and crawling) were typically shorter than resting dives, while foraging dives were equally likely regardless of dive duration. The short dive durations observed in this study suggest that, in shallow water habitats, juvenile green turtles dive with only partially inhaled lungs to remain negatively buoyant. This could also explain why surface interval exhibited a notably strong influence on dive durations as turtles may need to rely more on blood oxygen stores (which can be replaced over multiple breathing events) than lung oxygen stores while diving. Furthermore, the limited lung oxygen stores could explain why increased activity patterns were typically associated with shorter dives. Our findings suggest that sea turtles diving in shallow water habitats may dive with their lungs only partially full, and thus will limit oxygen stores. This has important conservation implications, as sea turtles caught in fishing nets in shallow waters could drown faster than those caught in deeper water habitats.

Background: Understanding dispersal of sea turtles during the juvenile stage, known as “lost years”, is a key step to be able to protect them. To fill this gap, modeling is an available strategy. This is the purpose of the Sea Turtle Active Movement Model (STAMM): a Lagrangian model which simulates sea turtle trajectories under combined effects of oceanic drift and habitat driven swimming activity. In this work, we study a simplified form of the STAMM parameterization of the habitat-driven swimming velocity adapted for loggerhead sea turtles. We seek to calibrate it directly using satellite tracked trajectories of juvenile loggerheads in North Pacific from NOAA PIFSC Marine Turtle Research Program.

Methods: The modeled habitat depends on the Sea Surface temperature and a proxy for food abundance. Several food proxies are tested. A Kolmogorov Smirnov based metric is defined to compare spatial distribution of simulated turtles with observed turtles. Then, the model main parameters are estimated from sensitivity analysis to calibrate the model.

Results: Results suggest that, in that modeling context, (1) chlorophyl-a concentration is the most appropriate proxy for food abundance and (2) meridional movements of satellite tracked turtles, which describe a clear seasonal cycle, are well reproduced by STAMM simulated trajectories. However, some of the parameter optimal values, such as preferred temperature range and the distance over which habitat gradients are computed are unexpected and thus questionable.

Conclusion: This work provides the first simulations of juvenile loggerhead trajectories using a simplified version of STAMM directly calibrated using satellite tracking data. The simulated spatial dispersal is statisfactory but is obtained with some unexpected parameter values.This suggests that further work is needed to improve the formulation of the used habitat and/or swimming velocity models.

Marine plastic debris poses significant threats to marine wildlife, particularly sea turtles. Plastic debris found in digestive tract and cases of mortality have been reported globally. Many previous studies focused on colour and texture suggested that visual similarity between plastic and jellyfish (their common prey) may lead to mis-ingestion. However, animal-borne camera videos on juvenile green turtles (Chelonia mydas) have shown that not all encountered plastic debris was ingested under natural environments (61.8% encounter-ingestion ratio). Therefore, the mechanisms behind mis-ingestion remain unclear. Biofouling is known to occur almost everywhere in the ocean, thus long persistent marine plastic debris is a target for attaching microorganisms. Such biofouling may alter properties of plastic debris in ways that could influence ingestion behaviour in sea turtles. We hypothesized that biofouling may make plastic debris more attractive to green turtles and aimed to further understand the key sensory behind the mis-ingestion.

To test this hypothesis, we conducted a series of experiments. In the first experiment (A), biofouling was artificially carried out on plastic sheets for 3 weeks allowing attachment of microorganisms. Then, the cultivated samples and clean plastic samples were displayed separately in random order (9 displays per sample type per individual and each display last for 5 minutes) to 12 juvenile green turtles. The bite actions towards samples were counted. Since biofouling not only altered the colour of the plastic sample but also emitted odours, two subsequent behavioural experiments (B: I. & II.) were conducted to investigate the role of in-water chemical cues and visual cues in attracting sea turtles to plastic debris. In experiment B, 8 juvenile green turtles were exposed to: I. (chemical cues): bio-fouled samples sealed in a zip bag with no holes (no chemical cues; denoted as [FI]) and with holes (chemical cues present; denoted as FI) and II. (visual cues): brownish bio-fouled plastic ([FII]) and translucent clean plastic ([CII]), both sealed in zip bags to prevent the release of chemical cues into the water. During these experiments, several behaviours of turtles were observed including noticing, close observing or touching, attempting to bite and actual biting. Except noticing, all other reactions (referred to as positive interactions) were recorded.

The results of experiment A showed that the turtles were significantly more likely to bite bio-fouled samples with 24 bites compared to 9 bites on clean samples (Turkey pairwise, p = 0.009). According to experiment B, a total of 39 positive interactions were seen towards FI (bio-fouled samples with chemicals) but only 20 towards [FI] (no chemicals released from bio-fouled samples) in experiment I (c² test, p <= 0.002). In contrast, no differences (c² test, p = 0.062) can be seen in experiment II (22 for [FII] vs. 19 for [CII]). Our findings suggest that biofouling can play a crucial role in the mis-ingestion of plastic debris and water-borne chemical cues from biofouling were a stronger attractant than visual cues.