A Baseline Model For Estimating the Risk of Gas Embolism in Sea Turtles During Routine Dives

Sea turtles, like other air-breathing diving vertebrates, commonly experience significant gas embolism (GE) when incidentally caught at depth in fishing gear and brought to the surface. To better understand why sea turtles develop GE, we built a mathematical model to estimate partial pressures of N2 (PN2), O2 (PO2), and CO2 (PCO2) in the major body-compartments of diving loggerheads (Caretta caretta), leatherbacks (Dermochelys coriacea), and green turtles (Chelonia mydas). This model was adapted from a published model for estimating gas dynamics in marine mammals and penguins. To parameterize the sea turtle model, we used values gleaned from previously published literature and 22 necropsies. Next, we applied this model to data collected from free-roaming individuals of the three study species. Finally, we varied body-condition and cardiac output within the model to see how these factors affected the risk of GE. Our model suggests that cardiac output likely plays a significant role in the modulation of GE, especially in the deeper diving leatherback turtles. This baseline model also indicates that even during routine diving behavior, sea turtles are at high risk of GE. This likely means that turtles have additional behavioral, anatomical, and/or physiologic adaptions that serve to reduce the probability of GE but were not incorporated in this model. Identifying these adaptations and incorporating them into future iterations of this model will further reveal the factors driving GE in sea turtles.

MENDUKUNG UPAYA PERLINDUNGAN PENYU BELIMBIMG (Dermochelys coriacea) MELALUI PENDIDIKAN (PROGRAM KKN WAU-WEYAF, ABUN)

ABSTRACT Wau-Weyaf Beach is the nesting ground of six species of turtles, including the world's largest turtle, the leatherback turtle (Dermochelys coriacea). The University of Papua (UNIPA) Manokwari, since 2009 has been directly involved in the turtle nesting area protection program by involving the students of UNIPA through the Community Service Program (KKN). In 2016, students carried out the KKN Program starting from June 30th to August 16th in Kampung Wau-Weyaf, one of the leatherback turtles’ egg-laying locations in Abun. This paper is a part of the Community Service Program which is carried out in the said village. The activities conducted during the KKN include both formal and non-formal education, religious education, and environmental education. Education-based KKN directly helps to improve public awareness which, in turn, supports the efforts to protect and save the leatherback turtles (Dermochelys coriacea) on the coast of Abun, Tambrau. The same approach is also able to improve the calistung (the capability to read, write, and count) ability of school children along with their awareness to maintain the cleanliness of their homes, school, and village environment. Keywords: Education; Conservation; Turtle; Wau-Weyaf ABSTRAK Pantai Wau-Weyaf merupakan tempat bertelur bagi 6 jenis penyu, termasuk penyu terbesar di dunia, Penyu Belimbing (Dermochelys coriacea). Universitas Papua (UNIPA) Manokwari, sejak tahun 2009 telah terlibat secara langsung dalam program perlindungan kawasan peneluran penyu ini melalui pelibatan mahasiswa melalui program Kuliah Kerja Nyata (KKN). Pada tahun 2016, mahasiswa Universitas Papua (UNIPA) melaksanakan program KKN yang dilaksanakan antara tanggal 30 Juni sampai dengan 16 Agustus 2016 di Kampung Wau-Weyaf. Tulisan ini merupakan bagian dari pelaksanaan kegiatan KKN yang dilaksanakan di kampung Wau-Weyaf sebagai salah satu lokasi peneluran telur penyu belimbing di Abun. Kegiatan yang dilakukan meliputi pendidikan formal dan non-formal, pendidikan agama, dan pendidikan lingkungan. KKN berbasis pendidikan yang dilakukan secara langsung membantu meningkatkan penyadar tahuan masyarakat yang menunjang usaha perlindungan dan penyelamatan penyu belimbing (Dermochelys coriacea) di pesisir Abun, Tambrau. Pendekatan yang sama juga mampu meningkatkan kemampuan calistung anak-anak sekolah dan kesadaran menjaga kebersihan lingkungan rumah, sekolah dan kampung. Kata kunci: Pendidikan; Konservasi; Penyu; Wau-Weyaf

Leatherback Turtles in the Eastern Gulf of Mexico: Foraging and Migration Behavior During the Autumn and Winter

We deployed 19 satellite tags on foraging adult leatherback turtles, including 17 females and 2 males, captured in the northeastern Gulf of Mexico in 2015, 2018, and 2019 in order to study regional distribution and movements. Prior to our study, limited data were available from leatherbacks foraging in the Gulf of Mexico. Tag deployment durations ranged from 63 to 247 days and turtles exhibited three distinct behavior types: foraging, transiting, or rapidly switching between foraging and transiting. Some females were tracked to nesting beaches in the Caribbean. Most of the leatherbacks remained on and foraged along the west Florida continental shelf whereas a few individuals foraged in waters of the central Gulf of Mexico during the autumn and winter. In addition, migration of adult females through the Yucatan Channel indicate that this is a seasonally important area for Caribbean nesting assemblages.

The Effects of Nest Location and Beach Environment on Hatching Success for Leatherback (Dermochelys Coriacea) and Green (Chelonia Mydas) Sea Turtles on Bioko Island, Equatorial Guinea

Hatching success in sea turtles is hindered by a variety of biotic and abiotic factors. This study of the nesting ecology of leatherback (Dermochelys coriacea) and green (Chelonia mydas) sea turtles, investigated how several environmental factors and beach characteristics on Bioko Island, Equatorial Guinea influence sea turtle reproductive success. Average clutch hatching success was 40.4% for green turtles and 41.73% for leatherback turtles. For leatherback turtles, clutch elevation relative to the high tide line (HTL) was found to be the most influential factor in determining hatching success, highlighting the sensitivity of this species to sea level rise (SLR). Multiple linear regression analysis demonstrated that nest distance to vegetation and sand conductivity also played significant roles in leatherback clutch hatching success. For leatherback clutches, 33% percent of experimental nests were affected by inundation and 17% by predation. An optimum clutch elevation range for leatherback turtles was identified, where a distinct increase in hatching success was observed between -0.286 m to -0.0528 m above the HTL. For green sea turtles, 64% of experimental nests were affected by predation, confounding conclusions about the roles of environmental characteristics in green turtle hatching success. We propose further investigation into influential characteristics in green turtle nests and confirmation of the observed optimum elevation range on Bioko Island and other nesting grounds. Identified sensitivities of each species to SLR and beach characteristics will be used to encourage the government of Equatorial Guinea to consider the vulnerability of their resident turtle populations when planning for future coastal development.

Comparing Dynamic and Static Time-Area Closures for Bycatch Mitigation: A Management Strategy Evaluation of a Swordfish Fishery

Time-area closures are a valuable tool for mitigating fisheries bycatch. There is increasing recognition that dynamic closures, which have boundaries that vary across space and time, can be more effective than static closures at protecting mobile species in dynamic environments. We created a management strategy evaluation to compare static and dynamic closures in a simulated fishery based on the California drift gillnet swordfish fishery, with closures aimed at reducing bycatch of leatherback turtles. We tested eight operating models that varied swordfish and leatherback distributions, and within each evaluated the performance of three static and five dynamic closure strategies. We repeated this under 20 and 50% simulated observer coverage to alter the data available for closure creation. We found that static closures can be effective for reducing bycatch of species with more geographically associated distributions, but to avoid redistributing bycatch the static areas closed should be based on potential (not just observed) bycatch. Only dynamic closures were effective at reducing bycatch for more dynamic leatherback distributions, and they generally reduced bycatch risk more than they reduced target catch. Dynamic closures were less likely to redistribute fishing into rarely fished areas, by leaving open pockets of lower risk habitat, but these closures were often fragmented which would create practical challenges for fishers and managers and require a mobile fleet. Given our simulation’s catch rates, 20% observer coverage was sufficient to create useful closures and increasing coverage to 50% added only minor improvement in closure performance. Even strict static or dynamic closures reduced leatherback bycatch by only 30–50% per season, because the simulated leatherback distributions were broad and open areas contained considerable bycatch risk. Perfect knowledge of the leatherback distribution provided an additional 5–15% bycatch reduction over a dynamic closure with realistic predictive accuracy. This moderate level of bycatch reduction highlights the limitations of redistributing fishing effort to reduce bycatch of broadly distributed and rarely encountered species, and indicates that, for these species, spatial management may work best when used with other bycatch mitigation approaches. We recommend future research explores methods for considering model uncertainty in the spatial and temporal resolution of dynamic closures.

Leatherback turtles (Dermochelys coriacea) in the Gulf of Venezuela: An update stranding assessment 2001-2014

Leatherback turtle (Dermochelys coriacea) is highly impacted by fisheries’ bycatch worldwide. This study updates and estimates the leatherback turtle stranding records from 2001 to 2014 in the Gulf of Venezuela. Eighty-six stranded leatherback turtles were documented in the coast of the Gulf of Venezuela. Immature leatherback turtles were the most affected (85.1%) and the highest number of strandings were recorded during the dry season (55.8%). Our findings represent the minimum estimate of stranding events for the Gulf of Venezuela, especially considering the current lack of fisheries regulations. This is the latest update for the leatherback turtle strandings in the Gulf of Venezuela and could help to create new management solutions in the area aiming to minimize the impact on leatherback turtle populations in the Caribbean.