ISTS42 Program/Agenda

In the Saudi Arabian Red Sea, two of the seven species of sea turtles are known to nest and forage along the coast, the hawksbill turtle (Eretmochelys imbricata) and the green turtle (Chelonia mydas). Under Saudi Arabia’s Vision 2030 and the recent opening of its borders to recreational tourists, the country aims to develop several large-scale projects along the Red Sea coast, locally known as “giga-projects”. Thus, imminent pressures from coastal development highlight the urgency needed for multi-country cooperation in protecting sea turtles in the region. Importantly, turtles in the Red Sea are largely understudied, and we are lacking data on their main threats and heath status. This presentation will discuss broadly the current research status of turtles in the region, and some of the threats turtles are facing. Specifically, threats from climate change, plastic ingestion, heavy metal contamination, and coastal development. Hatchling success was found to be low (37%) in the northern Red Sea, likely due to high temperatures and low moisture. This raises concern with projected rising temperatures with climate change. Plastic ingestion was found to be a moderate threat, with 4 out of 10 turtles necropsied found with plastic particles > 1 mm in their digestive tract. Heavy metals also present a threat because the largest nesting site in the Red Sea is located next to a cement factory. Sand was collected at four nesting beaches near the factory and we found that heavy metal contamination was higher at the nesting beaches upwind compared to downwind. Major data gaps remain in the region, including identifying the cause of low hatching success. Coastal development will be a major threat in the future, and care should be taken to maintain and improve current foraging and nesting habitats.

In Indonesia, bycatch poses a significant threat to marine endangered species, including sea turtle populations, mainly where purse seine and gillnet fishermen are regularly operated. Because most bycatch data is not well recorded, there are numerous information gaps in various areas with a high potential for bycatch due to the number and operation of specific fishing gears. Typically, fishermen do not report data due to apprehension about interacting with law enforcement officers, or it is ignored because it is not a target catch. By involving about eleven local champions who are a combination of observers, crew members, and captains, monitoring was conducted from January 2022 to June 2023 in 6 locations in Indonesia include Muncar (East Java), Pekalongan (Central Java), Paloh (West Kalimantan), Derawan (East Kalimantan), East Flores (East Nusa Tenggara), and Alor (East Nusa Tenggara) with a total of 3.568 trips (524 gillnet trip and 3,044 purse seine trips) with a total of 123 turtle individuals consisting of Chelonia mydas 73,9% (n=91), Eretmochelys imbricata 10,57% (n=13), and Lepidoncheys olivacea 15,44% (n=14) and unidentified species 4,06% (n=5). About 106 individuals (86.18%) of turtles were reported released by fishers. The factor of turtle release was done because fishermen realized that the species had been protected by the national regulation of Law No. 5 of 1990 concerning the Conservation of Natural Resources and Ecosystems. In addition, bycatch handling training was also conducted for around 494 people during the monitoring period. However, in-depth research related to post-release bycatch needs to be conducted to determine the resilience of the turtles, and the role of local champions in releasing bycatch can more effectively benefit the turtle population in Indonesia.

Fisheries bycatch is a primary threat to sea turtles globally. A key step to limiting sea turtle bycatch in commercial fisheries is understanding when and where sea turtles interact with those fisheries. These location data are often difficult to obtain, especially for pelagic environments. Fisheries observer records are one potential strategy for obtaining location-specific data on where interactions occur. Observer data can then be used to build distribution models, a common technique that combines species’ presence or absence records with environmental data to develop predictive maps of species distributions. However, sea turtle bycatch in many pelagic fleets is a rare event and the resulting small sample sizes make it difficult to identify environmental drivers of bycatch and make inferences on new data. As a result, other sources of location information may be needed to supplement observer data.

One potential source of data is satellite telemetry, although these data come with their own caveats. Satellite telemetry only provides information on where individual turtles are, not where they are not. This presence-only data requires researchers to generate pseudo-absences (i.e., random points that represent where animals could have gone, but did not) and the method used to do so can strongly affect results. In turn, using telemetry-derived models to predict bycatch neglects a key piece of the puzzle: fishers do not randomly sample the environment but bias their sampling towards some areas and environmental conditions in ways that telemetry-derived models do not account for. Finally, satellite telemetry data are not always available due to logistical reasons and developing methods to use fisheries-dependent data to accurately predict species distributions can increase ecological understanding at minimal cost. Our goal here is to attempt to reconcile fisheries-dependent and telemetry-derived models in order to increase our ability to use both data sources to predict the spatial distribution of both fisheries interactions and bycaught species in the future.

We compared these two approaches for central north Pacific loggerheads using satellite telemetry data deployed on 428 loggerheads from 1997-2023 and fisheries bycatch records from the Hawaii shallow-set longline (SSLL) fishery from 2005 to 2021 (224 interactions out of 18,998 longline sets). We used Ensemble Random Forest (Siders et al. 2020), developed to predict rare events, to build the models for both datasets. Preliminary attempts to combine satellite telemetry data with kernel density-based pseudo-absences to predict SSLL loggerhead interactions have been mostly unsuccessful. However, we will explore new methods of pseudo-absence generation (e.g., correlated random walks), data subsetting, and environmentally-based weighting of longline sets to test whether these help reconcile the two data sources. Test data performance for observer record-based distribution models indicate better, but still relatively poor (mean area under the specificity/specificity curve: 0.65), performance that varies among years. We will discuss pros and cons of using each data source for distribution modeling and bycatch prediction, including the scope of inference for changing distributions with climate change, how to increase the utility of satellite telemetry data for predicting bycatch, and recommendations for future work.

Anthropogenic threats continue to impact marine turtle populations in the Philippines. As a country with an estimate of over 2 million small-scale municipal fishers across its archipelagic geography, it is difficult to monitor their catch and landing activities. Until recently, minimal attention has been given to the incidental take of turtles in these fisheries because of their perceived low ecological impact. Current data on non-targeted catch in small-scale fisheries is often inadequate and obscures our understanding of turtle bycatch and mortality.

Rapid bycatch assessments through semi-structured interviews were used to gather baseline information on turtle bycatch in small-scale municipal fisheries in the Philippines. To date, surveys were conducted in 6 provinces, spanning 61 villages in 14 municipalities and 2 cities, and carried out a total of 1,694 household interviews, 128 key informant interviews, and 107 focus group discussions. For the preliminary results here, we focus only on characterizing turtle bycatch in small-scale municipal fisheries in Northern Palawan, Philippines. In this region, we completed 989 semi-structured household interviews in 17 villages across 3 municipalities and 1 city. Only direct experiences from the respondents within the last 3 years prior to the interviews were analyzed to reduce the effect of memory decay on the results. A total of 642 bycaught individual turtles were reported in the household interviews, with the most species being identified as green turtles Chelonia mydas (n=313) and hawksbill turtles Eretmochelys imbricata (n=119). Most of the bycatch incidents involved bottom-set gillnets (n=182), drift gillnets (n=153) and fish corrals (n=118). Most of the turtles found in the gears were reported as alive (n=633) and released, with 1 reported to be consumed; however, it is possible that mortality and consumption of turtles were underreported in the household interviews. Out of the 642 individual bycatch from the respondents, only 0.01% (n=9) were reported to local authorities.

The initial findings in Northern Palawan underscores the utility of rapid bycatch assessment interviews in capturing data on the overlap between small-scale municipal fisheries and threatened species; particularly, in identifying priority sites for landing monitoring and bycatch mitigation, and in determining the fishing gears with high turtle bycatch incidence and their characteristics. Data collected from the rest of the sites will be important in filling in key knowledge gaps beyond Northern Palawan, thereby providing a better understanding of the ecological impact of incidental take in small-scale fishing operations within Philippine municipal waters, which is crucial in determining ways forward for policy and management.

Sea turtles are largely impacted by industrial fisheries worldwide. Although strategies for at-sea risk mitigation exist, bycatch avoidance remains challenging because they are highly mobile and use a variety of habitats throughout their life cycle. To precisely identify the places and times where they might interact with fisheries, a thorough characterization of their habitat is required. We address this for large juvenile loggerhead turtles (Caretta caretta) in the open waters of the Western Indian Ocean (WIO). In the WIO, loggerhead turtles use large oceanic areas to forage where they risk being caught by fisheries targeting large pelagic fish (e.g., drifting longlines and purse seines). Our study focuses on the spatiotemporal overlap between drifting longlines, using fishing hours of AIS-tracked vessels provided by the Global Fishing Watch, and loggerhead turtle foraging habitat. We identified foraging behaviour (1333 daily locations) along the tracks of 39 late-juvenile individuals (mean curved carapace length = 71.27 cm; SD = 5.89 cm) using Hidden Markov Models and we extracted a series of oceanographic variables (e.g., sea surface temperature, eddy kinetic energy, micronekton biomass) from global ocean reanalyses (accessed via AVISO+ and CMEMS) at those locations and randomly sampled ones (i.e., pseudo-absences). We used an ensemble modelling approach, combining 10 machine learning algorithms (e.g., Random Forest, multivariate adaptive regression spline, support vector machine, artificial neural network), to produce daily maps of foraging probability between June 2017 and May 2020. We found different overlap trends, measured as the percentage of fishing hours in core foraging area (i.e., foraging probability > 0.75), between the Northwestern Indian Ocean (NWIO) and the Southwestern Indian Ocean (SWIO). In the NWIO, we found a decreasing overlap with no clear seasonality whereas, in the SWIO, we found a consistent seasonal overlap with > 50% of fishing hours in core foraging area from April to mid-September and almost no overlap the rest of the year. In the NWIO, areas of high overlap are scattered across a wide latitudinal range (10°S to 20°N) whereas, in the SWIO, they are concentrated within a 10° latitudinal band (30°S to 40°S). By identifying periods and areas of high interaction risk, our study will prove useful to promote dynamic management of fisheries and reduce bycatch of loggerhead turtles in the WIO.

Iran is among the top fishing nations in the northwestern Indian Ocean. The capture fisheries production in the Iranian waters of the Persian Gulf and the Gulf of Oman has been steadily increasing and has more than doubled over the last two decades from ~261k tonnes in 2001 to 672k in 2022. The area includes critical habitats for green and hawksbill turtles that are dominant, olive and loggerhead turtles that occasionally, and leatherback turtles that rarely occur. Consequently, bycatch, the unintentional catch in fishing gear, occurs where the critical habitats and fishing grounds overlap. While marine turtles are nationally protected, and their nesting beaches in the area are relatively well-known with ongoing protection efforts, the turtle bycatch hotspots along the national waters are entirely unknown. This study used an interview-based investigation as a cost-efficient approach to fill this knowledge gap. We interviewed local fishers and collected information about where they observe turtles and where they fish, which were marked on easy-to-use maps at different scales printed on dry-erase surface sheets. The interviewees were asked to mark places by drawing polygons on the maps, which were transcribed electronically to Google Earth and saved as KML files. Finally, QGIS was used to process spatial data and develop hotspot maps. The output layer values on the maps were subdivided into five levels, each representing the degree of overlap between a fishing pressure (i.e., all gears, gillnet, trawl, longline) and turtle distribution, including Light (<20%), Medium Light (20-40%), Moderate, (40-60%) Medium Heavy (60-80%), and Heavy (>80%). Maps were drawn based on information collected by interviewing 264 fishers from 47 fishing communities. The results showed that whilst in-water turtles are distributed along the whole coastline, they are mainly abundant in coastal waters surrounding the Persian Gulf’s islands, notably Larak, Hengam, north of Qeshm, Lavan, Nakhiloo, Khark, and Kharko. All these places include shallow, relatively sheltered coral reef habitats and seaweed and seagrass beds, which are probably more suitable feeding grounds for marine turtles than the usually exposed coastal waters of the Gulf of Oman. These biologically productive coastal areas, however, are also extremely attractive to fishers. Therefore, it is unsurprising that for all gears together, and for gillnet, the most widespread fishing gear used in the area, precisely the same places, were identified as bycatch hotspots (i.e., medium to heavy values). Although not as severe as gillnet, longline, and trawl appeared as threats around Nakhiloo, Khark, and Kharko islands. In conclusion, fisheries in Iranian waters impact marine turtles surrounding nearshore islands of the Persian Gulf, and gillnets are the primary source of risk. These findings show the high-risk turtle habitats in the area for the first time, focusing future management efforts from the vast over 2250 km Iranian coastline to much smaller and more manageable units.

Bycatch of sea turtles in fisheries is one of the main contributors of population declines globally. Mitigation techniques have been developed for some fisheries, but adoption of these techniques across fishing sectors is often precluded by gear configurations, vessel designs, operational characteristics, fishing methods or fisher cultures and customs across fleets. While more effective and fishery-specific mitigation techniques are under development, it is imperative to introduce fishers to handling and release methods to improve the survival of captured individuals after release. This is particularly critical in surface longline fisheries, where the use of best handling and release practices (BHRP) have been shown to reduce post-release mortality significantly. Many initiatives have already taken place in different countries to develop and implement BHRP of sea turtles, and several countries and fishery bodies have adopted regulations requiring fishers to complete trainings on BHRP, and to carry a set of tools on board. In the past 10 years, the authors have worked with different teams, and hand in hand with artisanal and industrial longline fisheries and authorities, in Spain and America (mainly in Mexico, Guatemala, Costa Rica, Panama, Ecuador and Peru) to help develop BHRP and carry out in-person trainings. This work has always included initial meetings with fishers and with authorities, and visits to fishing harbors when possible, to fully understand the fishery before making any recommendations or proceeding with trainings, and for mutual learning between professionals and fishers. 1,900 fishers and government authorities have been trained so far during this effort. This work has shown that, although general best practices for surface longline fisheries do exist and are commonly applied, they should not be used as such, since without refining they may even recommend practices or tools that are detrimental to sea turtle post-release mortality (e.g., recommending the use of long-handled line-cutters to a fishery that uses a steel leader) or that are not applicable in the condition of the fishery (e.g., obligatory use of a dipnet for small boats). There is no “one-size-fits-all” recipe. Instead, BHRP and national and regional policies should be tailored and adapted to the singularities of each fleet and fishery, or even community, based on factors such as fishing gear, vessels used, socio-economic situation of the community, availability of tools in the domestic market or fishing operations. Local ecological or traditional knowledge and co-design of the BHRP have proven to be a win-win solution for fisheries and conservation of sea turtles. This work has also identified the challenges to institutionalize the trainings and building capacities for the long-term.

Sri Lanka is situated in the East West trade path of the Indian Ocean where over two thirds of world’s oil shipments and one third of bulk cargo are transported. X-Press Pearl was a container ship registered in Singapore which arrived in off Colombo port on 19^th May 2021 engulfed in flames. After burning for 12 days, finally the ship sank on 2^nd June 2021 while towing to the deeper waters. The ship was carrying 1,486 containers including 25 tons of nitric acid, 42 different kinds of other chemicals, urea, cosmetics, low-density polyethylene (LDPE) pellets etc.

The detrimental impacts to the marine environment, fisheries sector, tourism sector, wildlife conservation sector and day to day life of many coastal communities are yet to be fully assessed and recovery efforts may take long period to achieve the successful results.

433 sea turtles have died and washed up on Sri Lankan beaches. The carcasses include critically endangered Hawksbill sea turtle (Eretmochelys imbricata), endangered green sea turtles (Chelonia mydas), leatherback turtles (Dermochelys coriacea) and olive ridley turtles (Lepidochelys olivacea). In addition to the sea turtles, more than 20 dead dolphins and 7 dead whales have been recorded after the X-Press Pearl ship disaster. Since only small portion of the dead animals wash ashore (between 10-20%) and the rest could be sunk in the bottom of the ocean or carried away from the beach by the currents, the true numbers of affected and dead animals could be more than 2000. The Department of Wildlife Conservation (DWC) collects the carcasses and conducts the postmortem and then sends same tissue samples to the government analysts department for postmortem report. However, none of the postmortem reports have been released and therefore, the exact cause of death is not yet known.

We have observed some forms of chemical burning on the surfaces of the bodies of the dead turtles and dolphins, even dissolving their skins and shells. In addition, oral and cloacal bleeding was observed. Some chemicals and plastics that are reported to have been in the X-Press Pearl ship are commonly associated with toxic additives or monomers which are known to have impacts on the marine environment. Some of the monomers making up the polymers are intrinsically hazardous (e.g., Polystyrene, PVC). Additive chemicals are not strongly bound within the plastic matrix and therefore will tend to leach into the surrounding environment. Among the most hazardous additive types are brominated flame retardants, phthalates, and lead compounds.

X-Press Pearl was carrying oil, petroleum and PCBs which can lead to marine pollution. Heavy metals such as lithium and cadmium could also cause the development of cancers among the marine fauna such as fibropapilomatosis in sea turtles. Impacts on ecosystem services from the marine environment, irreversible impacts on mangrove ecology, marine biodiversity, and coastal ecology - changes in marine water quality and the population dynamics of species composition needs to be fully investigated.

Ocean plastic pollution causes numerous ecological impacts on thousands of marine species. Floating plastics can accumulate in subtropical gyres, and a very high concentration of this type of pollution is found in the eastern portion of the North Pacific subtropical gyre – an accumulation area known as the “North Pacific Garbage Patch” (NPGP). The Ocean Cleanup is a non-profit organization developing a cleanup system to remove plastic debris afloat in the NPGP. Cleanup operations began in these international waters in August 2021, and created a unique opportunity to collect biological data in the region, with continuous monitoring efforts to better understand the local environment and minimize potential negative impacts of cleanups on marine life, including sea turtles. In over 7,000 hours of towing operations conducted between August 2021 and November 2023 in the NPGP, we observed 75 sea turtles through different methods (above-water sightings, underwater observations through cameras, incidental capture and encounter of biological remains). The observed turtles included 33 loggerheads (Caretta caretta), 14 greens (Chelonia mydas) and 3 olive ridleys (Lepidochelys olivacea); in 25 observations, species identification was not possible. Most turtles were juveniles, with only one confirmed record of an adult (a female olive ridley turtle). Analysis of gastrointestinal tract contents of some individuals revealed 100% frequency of occurrence of plastic ingestion for the analyzed loggerhead (n = 10), green (n = 6) and olive ridley (n = 1) turtles. Individuals ingested from less than 10 to over 300 plastic items (with >1mm), primarily fragments and lines, with green turtles ingesting the highest numbers of items. Although no direct health effects (e.g. lesions, blockage) were noted in the turtles’ gastrointestinal tracts, plastic ingestion could have contributed to their mortality through sub-lethal effects. In fact, most of the deceased turtles presented low fat reserves, atrophied muscles, and general signs of malnutrition. An additional impact recorded for sea turtles at the NPGP was entanglement, with 5 juvenile turtles observed entangled in ghost fishing gear. This shows that legacy plastic pollution in the North Pacific subtropical gyre impacts juvenile sea turtles in the region through ingestion and entanglement and reinforces the need for conducting cleanups at plastic accumulation areas. While the cleanup system has several mitigation measures in place (green LED lights, breathing areas, escape routes, emergency release mechanisms, operational strategies), efforts to further develop deterrent and mitigation measures that decrease the possibility of negative outcomes in sea turtle encounters are currently a priority.