Exclusive Economic Zone Research Articles

PERUBAHAN NAMA ZONA EKONOMI EKSKLUSIF INDONESIA DI LAUT CINA SELATAN MENJADI LAUT NATUNA UTARA (1982-2017)

This research aims to describe the events behind the change of name of Indonesia's exclusive economic zone in the South China Sea to the North Natuna Sea and its impact from a historical perspective. This research uses the historical method with Miles and Huberman analysis techniques. The results of this study reveal that China made claims to the SCS based on historical claims prior to the 1982 UNCLOS which were unilateral in nature and caused conflicts and violations of Indonesia's sovereign rights in the SCS, causing Indonesia to react by changing the name of the EEZ in the SCS to the North Natuna Sea in 2017.

Global assessment of marine plastic exposure risk for oceanic birds

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.

Alleged Violations of Sovereign Rights and Maritime Spaces in the Caribbean Sea: Implications for the Customary International Law of the Sea

The International Court of Justice’s judgment in Alleged Violations of Sovereign Rights and Maritime Spaces in the Caribbean Sea reflects one of the most significant contributions the Court has made to customary international law of the sea since the Anglo-Norwegian Fisheries case. This article assesses the Court’s findings in the 2022 judgment in relation to customary international law and the implications of the Court’s views for the law of the sea, especially as reflected in the UN Convention on the Law of the Sea. After providing a background to the legal proceedings between Nicaragua and Colombia, the discussion focuses on the respective rights and duties of states within the exclusive economic zone, artisanal fishing rights, straight baselines, and the contiguous zone. The article concludes with reflections on the interaction of the Court’s judgment with the UN Convention on the Law of the Sea.

Maritime Security in the Baltic and Japanese Straits From the Perspective of EEZ Corridors

This study focuses on the practice of the Baltic Sea coastal states and Japan in voluntarily limiting the outer extent of their territorial sea in straits. The reasons for the establishment of narrow exclusive economic zone (EEZ) corridors in straits are mostly related to security considerations. This article examines the consequences of such state practice for navigational regimes and for the protection of critical offshore infrastructure. It is argued that the abolition of an EEZ corridor results in the nominal increase of a coastal state’s sovereign territory, whereas it implies a decrease in the substantive scope of sovereignty over the relevant maritime area.

Legality of the Use of Armed Forces Against Foreign Parties Obstructing Efforts to Eradicate Illegal, Unregulated, Unreported Fishing in the Exclusive Economic Zone

The purpose of this research is to find out the legality of the entry of Chinese coastguards into Indonesia's EEZ to protect the Kway Fei 10078 Fishing Boat and to find out the legality of using armed forces against foreign parties who obstruct efforts to eradicate Illegal, Unregulated, Unreported Fishing in EEZ and to find out what actions Indonesia should take against China's actions. This study uses normative juridical research methods, namely looking for applicable provisions and library materials. Based on the analysis and research conducted, it was concluded that the entry of the Chinese coastguard into Indonesia's EEZ which protects the Kway Fei 10078 ship is illegal because other countries' ships are only given the right to sail, not protect other ships that violate other countries' EEZ areas according to Article 58 UNCLOS 1982. Retaliation for armed attacks against foreign parties that hinder the eradication of IUU Fishing can be carried out because the right of self-defense is granted by Article 51 of the UN Charter can be realized by a state that is harassed by foreign parties. The actions of disruptive foreign parties are usually in the form of bringing in warships or coastguards to carry out security.

Another Look at Marine Minerals

Abstract Deep-sea mining is taking another step closer to reality. Early leases for exploration in the central Pacific manganese nodule fields and elsewhere in the oceans are coming to an end, and contractors are faced with a choice—extend the licenses to continue exploration or apply to mine the deposits they have found. The first 15-year licenses were originally signed into effect by the International Seabed Authority (ISA) in 2001 and began to expire in 2016. With no operations in a position to commence mining and, more importantly, no regulations in place to allow it, most exploration licenses were simply renewed. Eight of the original licenses were extended for five more years, some twice, and new licenses have been granted. Today, there are 31 contracts for exploration: 19 for manganese nodules, 7 for sea-floor massive sulfides, and 5 for Co-rich crusts. The first contract for massive sulfide exploration expires in 2026; the first for Co-rich crusts expires in 2029. Meanwhile, there is strong interest from a number of countries in the mineral resource potential of their exclusive economic zones (EEZs), particularly Japan and Norway. Against this backdrop of rapidly shifting exploration activity, it may be time to take another look at marine minerals as a resource for the future. In a report entitled “The Future of the Ocean Economy by 2030,” the Organization for Economic Cooperation and Development (OECD) asked, “What new developments could result in a complete revision of offshore mineral potential?” For most parts of the oceans, the answer to this question is plagued by inadequate mapping and a lack of geologic knowledge as a basis for assessing the resources. However, new approaches to exploration are emerging, and recent discoveries, such as on the continental shelf and beneath the cover of sediment, are changing our view of the resource potential.

Seamount mining test provides evidence of ecological impacts beyond deposition.

In July 2020, Japan undertook the first deep-sea mining test of cobalt-rich crusts on the summit of Takuyo-Daigo Seamount within their exclusive economic zone (EEZ). Seabed mining regulations are currently being developed by the International Seabed Authority (ISA)1; however, a lack of experimental data has so far constrained our understanding of the associated impacts, particularly from the release of sediment plumes.2 The area of sediment re-deposition from the crust mining test was determined using modeled data and in situ observations. To investigate biological impacts, variations in seabed megafauna (animals>1cm) were quantified from seabed imagery collected around the excavation site before, 1month, and 13months after the test in areas both inside and outside (adjacent) expected deposition. Observable responses varied across community components: densities of sessile animals were similar between deposition and adjacent areas throughout the study; mobile epifauna were less abundant only in the deposition area following disturbance; and highly mobile swimmers showed reduced densities after the test in both deposition and adjacent areas following disturbance. These results stress that monitoring of highly mobile taxa may be essential to fully assess disturbance extent and magnitude. Fish may avoid areas even outside plume deposition, possibly owing to the creation of suboptimal feeding patches resulting from deposition. Our findings suggest sufficiently large (>300×300 m), distant, and representative control areas are essential to optimally map deep-sea mining impacts in ferromanganese crust habitats to ensure impact assessments encompass the full range of functional components in the megabenthic community (including mobile fishes) that typically inhabit seamounts.

Length-Weight Relationship of Four Species of Deep-Sea Congrid Eel (Congridae) from the Southwest Coast of India, Arabian Sea

Length-weight relationship was estimated for the deep-sea congrid eel species collected from the trawler landings at Kalamukku, of Kochi, Kerala and Colachel, of Kanyakumari, Tamil Nadu, Arabian Sea, southern India, between February 2021 and August 2022. The samples were obtained from the deep-sea trawlers, operated along the Exclusive Economic Zone of India, Arabian Sea with a cod end mesh size of 35 mm at 200–250 m depth. The estimated b values range from 2.80 to 3.19. Novelty of the study is providing length-weight relationship for two newly described eel species viz. Ariosoma indicum and A. maurostigma will help in the conservation and management of these species in the future.

Policy on Maritime Border Disputes Between Indonesia and Australia: Stephen M. Walt’s Neorealism Perspective

Indonesia is a maritime country with an Exclusive Economic Zone (EEZ) covering an area of 7.81 million square kilometers. Consequently, Indonesia has numerous disputes with neighboring countries regarding maritime boundaries in the EEZ, particularly with Australia. Several incidents have strained the relationship between the two countries. For example, from December 2013 to January 2014, there were six instances of the Australian Navy unintentionally violating Indonesian waters during border operations. Other issues include illegal fishing, human trafficking, illegal transshipment, and, more recently, an Australian warship's breach of Indonesian waters on September 8, 2022. Maritime boundary disputes occur when two or more countries have overlapping claims in the same maritime territory. These disputes can be caused by differences in the interpretation of international law, conflicting economic interests, historical or cultural claims, or geopolitical tensions between the involved nations. Maritime boundary disputes can be resolved through negotiations, international arbitration, mediation, or legal processes. In this case, the neorealism theory, developed by Stephen M. Walt, provides an understanding of international relations, changes in power structures, conflicts, cooperation among nations, and the factors influencing foreign policies. By applying Stephen M. Walt's neorealism theory, this study analyzes the policy frameworks of Indonesia and Australia in managing their international relations and the factors that have led to the disputes between the two.

ICJ의 1985년 리비아-몰타 사건과 대륙붕의 거리 기준 우위론

This article considers the theory of the primacy of the distance criterion over the natural prolongation under the continental shelf regime, which was resulted from the 1985 judgment of the International Court of Justice (ICJ) in the Libya/Malta case. In addition, an effort is made to suggest the influence on the Japan’s position as to the continental shelf in the East China Sea, including the issue of the 1974 Korea-Japan Joint Development Agreement (JDA), and further, draw implications for Korea and prospects in the East China Sea. The doctrine of the natural prolongation of the land territory suggested in the ICJ’s judgment in the North Sea Continental Shelf cases enabled Korea to conclude the JDA with Japan. However, shortly after, the introduction of the exclusive economic zone regime based on the distance criterion made the natural prolongation doctrine lose its power. Particularly, in the 1985 Libya/Malta case, the ICJ presented a ruling that could be misread as meaning that a State’s natural prolongation entitlement to a continental shelf beyond 200 NM cannot extend within 200 NM of another State. This judgment is presumed to have had some impact on Japan’s passive attitude toward the implementation of the JDA. Japan has taken the position that Korea’s continental shelf claim beyond 200 NM cannot be recognized legally in the East China Sea. However, this theory seems to be very doubtful because it ignores the natural prolongation entitlement without grounds. There was no subsequent case law that explicitly acknowledged the theory. In the ICJ’s pending case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 NM from the Nicaraguan Coast, the ICJ is addressing this issue now. In order to prepare for the future of the East China Sea, it is necessary to understand Japan’s relevant legal position and its basis. Moreover, particular attention should be paid to the forthcoming judgment in the abovementioned Nicaragua v. Colombia case.

A systematic conservation plan identifying critical areas for improved chondrichthyan protection in South Africa

The International Union for Conservation of Nature (IUCN) estimates that over a third of all chondrichthyan species (sharks, rays and chimaeras) are threatened with extinction, primarily by overfishing (as target or bycatch species). Owing to the wide-ranging distributions of many chondrichthyans, they are often overlooked in marine protected area (MPA) design. South Africa is a biodiversity hotspot for chondrichthyan species diversity, and to improve the conservation status of these species in the country's continental exclusive economic zone (EEZ), we collaborated widely to collate existing occurrence data. Ensemble models were developed for 87 species' distributions, which informed a systematic conservation planning analysis for 64 threatened and endemic species. We assessed the current representation of these species in South Africa's MPA network and identified priority areas for protection, avoiding fishing pressure where possible. Results show that many MPAs are well placed to protect chondrichthyans, especially along the east coast (KwaZulu-Natal province). Unfortunately, permissive fishing regulations within many MPA zones reduces their effectiveness at protecting chondrichthyans. Improved regulations designed to protect chondrichthyans within all MPAs should be considered a high priority. Priority areas for increased spatial protection were identified along the west coast continental shelf, the Agulhas Bank off the south coast, and south coast embayments. We found that supplementing the current MPA network by an additional 5 % of the EEZ would be sufficient to protect >30 % of the range of all 64 species, provided there is adequate enforcement. As South Africa prepares to expand its MPA estate to meet international targets, these findings can ensure that chondrichthyans are well represented.

Advances in Scale Assessment of Seabird Bycatch: A New Methodological Framework

This paper presents a methodology for indirectly estimating the scale of seabird bycatch using existing data. The study focuses on five key species of ducks that winter in the Polish waters of the Baltic Sea and are highly susceptible to bycatch: Long-tailed Duck, Velvet Scoter, Common Scoter, Greater Scaup, and Tufted Duck. The evaluation units used are divided into the Bornholm (BS) and Gotland Subdivisions (GS) within the Polish Exclusive Economic Zone (PEEZ). The analysis acknowledges the lack of bycatch data for certain areas known to have high concentrations of diving birds and fishing activity. The population sizes of waterbirds were assessed using ship-based surveys and a distance sampling approach. Fishing effort data from the five winter seasons between 2015/2016 and 2019/2020 were analyzed. Bycatch rates were estimated based on surveys conducted in previous seasons, and threshold values for bycatch were established using the concept of “small numbers” defined in EU directives. The results show that within the GS of the PEEZ, the estimated average abundance of all diving waterbirds was 174,800 individuals, with an average annual bycatch of 7921 birds (4.5% of the total). The Velvet Scoter was the most abundant species, followed by the Long-tailed Duck. In the BS, the estimated average abundance of diving waterbirds was 624,600 individuals, with an average annual bycatch of 5056 birds (0.8% of the total). The Long-tailed Duck was the most numerous species, followed by the Velvet Scoter. Acceptable bycatch thresholds were exceeded for all species in both subdivisions despite a much smaller scale of bycatch in the BS. The findings highlight the need for effective management and conservation measures to address the high mortality of seabirds due to bycatch. The methodology presented in this study offers a valuable approach for estimating bycatch scale and can support efforts to minimize the impact on seabird populations.

Movement patterns and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean: Insights from conventional tag release-recapture data

This study investigates the movements, patterns, and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean. Data were collected as part of the ICCAT Atlantic Ocean Tuna Tagging Programme (AOTTP) through conventional tag release-recapture experiments. The study analyzed data from 7870 tagged fish, of which 452 were recaptured between 2016 and 2020. The results indicated that little tunny could travel long distances, with some fish covering up to 600 Nm between Mauritania and Côte d’Ivoire. The movement patterns of tagged fish varied, and there appeared to be some exchange of fish between Senegal-Mauritania and the Gulf of Guinea through the Côte d’Ivoire Exclusive Economic Zone (EEZ). The recapture rate was the highest within the first month after release, with half of the tagged fish recaptured within this period, then approximately 17 % and 11.5 % of tagged fish were recaptured within 60 and 90 days, respectively. The size distribution of tagged and recaptured little tunny varied by area with statistically significant differences between Côte d’Ivoire – Gulf of Guinea and those from Mauritania to Liberia. The recaptured fish were larger than the tagged fish in all areas studied, suggesting a significant growth of individuals (4.2 cm per quarter). In conclusion, this study highlights the extensive movements and migration patterns of little tunny in the Eastern Central Atlantic Ocean. These findings suggest that factors such as Anchored Fish Aggregating Devices (AFAD) may influence the mobility of fish in certain areas and that the size distribution varies significantly between different regions.

Migration, breeding location, and seascape shape seabird assemblages in the northern Gulf of Mexico.

The Gulf of Mexico supports many seabird species, yet data gaps describing species composition and habitat use are prevalent. We used vessel-based observations from the Gulf of Mexico Marine Assessment Program for Protected Species to identify and characterize distinct seabird assemblages in the northern Gulf of Mexico (within the U.S. Exclusive Economic Zone; nGoM). Using cluster analysis of 17 seabird species, we identified assemblages based on seabird relative density. Vessel-based surveys documented the location, species, and number of seabirds across the nGoM between 2017-2019. For each assemblage, we identified the (co-)dominant species, spatial distribution, and areas of greater relative density. We also assessed the relationship of the total relative density within each assemblage with environmental, spatial, and temporal covariates. Of the species assessed, 76% (n = 13) breed predominantly outside the nGoM basin. We identified four seabird assemblages. Two assemblages, one dominated by black tern and the other co-dominated by northern gannet/laughing gull, occurred on the continental shelf. An assemblage dominated by sooty tern occurred along the continental slope into pelagic waters. The fourth assemblage had no dominant species, was broadly distributed, and was composed of observations with low relative density ('singles' assemblage). Differentiation of assemblages was linked to migratory patterns, residency, and breeding location. The spatial distributions and relationships of the black tern and northern gannet/laughing gull assemblages with environmental covariates indicate associations with river outflows and ports. The sooty tern assemblage overlapped an area prone to mesoscale feature formation. The singles assemblage may reflect commuting and dispersive behaviors. These findings highlight the importance of seasonal migrations and dynamic features across the seascape, shaping seabird assemblages. Considering the potential far-ranging effects of interactions with seabirds in the nGoM, awareness of these unique patterns and potential links with other fauna could inform future monitoring, research, restoration, offshore energy, and aquaculture development in this highly industrialized sea.

Dissolved fluxes of nutrients and carbon at the sediment-water interface in the Adriatic Sea: review of early data and methods from the Italian National Research Council (CNR)

We report the measurement of the Fluxes of Dissolved Compounds at the Sediment-Water Interface (DFSWIs), obtained by analyzing data collected in the Italian Exclusive Economic Zone (EEZ) of the Northern and Central Adriatic Sea from 1982. We also describe the methods, honed by Italy’s Consiglio Nazionale delle Ricerche (CNR), employed to measure and calculate DFSWIs, including benthic chambers and landers, sediment-water interface micro-profiling, on-board incubation, and pore water modeling. Data analysis demonstrated that in situ measurements are the most reliable approaches, but that on-board collected data also supply interesting results. The DFSWI data allowed to divide the Adriatic seafloor into areas with similar DFSWI types and intensities and to define the role of sediments as sources or sinks of chemicals such as nutrients, Dissolved Inorganic Carbon (DIC), and metals. DFSWIs mainly depend on dissolved and solid river inputs, Marine Organic Matter (mOM) production, and sediment reworking. They show a seasonal temperature-related trend, which in summer induces increased chemical reaction kinetics and microbial activity. DFSWIs decline from the Po River mouths southward, along the Holocene mud wedge. North of the Po River Delta, the DFSWIs are weaker and confined to the areas in front of the major river mouths, due to poor Organic Matter (OM) inputs and strong reworking of bottom sediments. The area south of the Po Delta cusp is characterized by strong DFSWIs, due to the high deposition of solid inputs from the Po River, strong primary production, and protection from the Western Adriatic Current and Bora storms; in summer, higher temperatures, and calm hydrodynamic conditions generate near-bottom hypoxic to anoxic environments in this area. In Northern and Central Adriatic offshore areas, negative DIC and phosphate fluxes are due to poorly reactive OM reaching this area and to the mainly carbonate composition and oxic environment of local bottom sediments. DFSWI data analysis highlighted the important contribution of sediments to marine carbon and nutrient cycles. This is particularly important for carbon, which plays a major role in seawater acidification and global climate change. The study also provides average DFSWI data for each diagenetic area, which allow calculating the carbon and nutrient budgets in the Adriatic Sea.

중국의 회색지대(Gray Zone) 전략과 우리 군의 대응 방안

In this article, I discuss China’s Gray Zone strategy, which involves increasing their naval power and using asymmetric tactics to become a rising maritime power. After examining this strategy, I then discuss the sources of conflict between South Korea and China, as well as our military’s response plan. The article also mentions that although South Korea and China established diplomatic relations in 1992, there are still many unresolved issues between two countries. Especially, issues such as the demarcation of the western sea border, development of the continental shelf, marine scientific research activities, and marine environmental conservation are still unresolved. Meanwhile, China is increasing its naval power and pursuing a Gray Zone strategy at sea using its Coast Guard(CCG) and Maritime Militia(PAFMM). Gray zone refers to the ambiguous middle ground between war and peace, and it refers to an indeterminate intermediate zone that does not belong to a specific area. China is pursuing a strategy that undermines the existing order by using gray zone operations in the maritime gray zones of countries with maritime territorial disputes and un-demarcated maritime boundaries in the East China Sea and South China Sea. By using non-military means, China is pursuing a “fait accompli” strategy through numerical superiority, gradualism, and repetitive activities while preventing the situation from escalating into armed conflict. China uses its Coast Guard and Maritime Militia as the main means of its gray zone strategy, which are essentially China’s second naval force and perform various missions on behalf of the People’s Liberation Army Navy. In Korea, there are many factors that cause conflicts with China in the ocean, such as the undefined Exclusive Economic Zone(EEZ) boundary and illegal fishing by Chinese vessels. China pursues a gray zone strategy to gain an advantageous position in future negotiations with Korea. Therefore, the Korean military must establish the following measures to protect its maritime interests. The response strategy below is based on a correct understanding of the gray zone strategy, which is part of China’s asymmetric strategy. First, in the event of a maritime dispute with China, governance should be established to integrate and operate available assets. Second, a cooperative system should be established to prevent accidental conflicts between Korea and China. Third, a naval forward base in the West Sea should be built to curb China’s eastward movement. Fourth, strategies should be sought to respond in conjunction with allies. Fifth, the military’s countermeasures and tactics for responding to the gray zone strategy should be developed.

A Quest for Meaning: Interpretation of Article 73(3) of the Law of the Sea Convention by Indonesian Supreme Court

Abstract In the spirit of conserving the balance between the interests of the coastal State and other States in the exclusive economic zone (eez), Article 73(3) of the United Nations Convention for the Law of the Sea (unclos) establishes that coastal State penalties for violations of fisheries laws and regulations may not include imprisonment or corporal punishment unless otherwise agreed by the States concerned. As one of the countries suffering from illegal fishing, Indonesia has seen a number of domestic cases challenging the practical application of Article 73(3) due to the failure of several offenders to pay monetary penalties for violating fisheries laws and regulations in Indonesia’s eez. Article 73(3) appears to be the only unclos provision that Indonesian courts have directly applied and interpreted into domestic cases. The debate revolves around whether courts can impose default confinement for fisheries offences in the eez. This article examines how Indonesian courts interpret the meaning and scope of the term ‘imprisonment’ within the ambit of Article 73(3) of unclos, particularly in the context of confinement for fine defaults, and whether international courts or tribunals provide any guidance in this interpretation.

Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints

Estimates suggest that over 4 gigatons per year of carbon dioxide (Gt-CO2 year−1) be removed from the atmosphere by 2050 to meet international climate goals. One strategy for carbon dioxide removal is seaweed farming; however its global potential remains highly uncertain. Here, we apply a dynamic seaweed growth model that includes growth-limiting mechanisms, such as nitrate supply, to estimate the global potential yield of four types of seaweed. We estimate that harvesting 1 Gt year−1 of seaweed carbon would require farming over 1 million km2 of the most productive exclusive economic zones, located in the equatorial Pacific; the cultivation area would need to be tripled to attain an additional 1 Gt year−1 of harvested carbon, indicating dramatic reductions in carbon harvest efficiency beyond the most productive waters. Improving the accuracy of annual harvest yield estimates requires better understanding of biophysical constraints such as seaweed loss rates (e.g., infestation, disease, grazing, wave erosion).

Accuracy Evaluation of Regional and Global Tidal Models (TPXO9 and Goddard Ocean Tide) at Kabil Tidal Station

Indonesia is an archipelagic country with a total marine area of 5.9 million km², consisting of 3.2 million km² of territorial waters and 2.7 km² of Exclusive Economic Zone waters, not including the continental shelf. With the vast waters in Indonesia, sufficient information about the tides is needed. Limitations of terrestrial tide data amidst the increasing need for marine information can be overcome by using global and regional tide models. This study uses the regional tidal data model released by BIG (Geospatial Information Agency) and the global tide model TPXO9 and GOT (Goddard Ocean Tides). From the two global tidal models, the tidal harmonic constant values are extracted at the tidal observation point in Kabil. Evaluation of global and regional tide models is carried out by comparing the amplitude values of the main harmonic constants of the tide models of global and regional tides with the amplitude values of the harmonic constants of terrestrial tidal measurement data to obtain a comparison of accuracy. The results of this research show the value of main tidal harmonic.

Spatial ecology and conservation of leatherback turtles (Dermochelys coriacea) nesting in Bioko, Equatorial Guinea.

Bioko Island (Equatorial Guinea) hosts important nesting habitat for leatherback sea turtles, with the main nesting beaches found on the island's southern end. Nest monitoring and protection have been ongoing for more than two decades, although distribution and habitat range at sea remains to be determined. This study uses satellite telemetry to describe the movements of female leatherback turtles (n = 10) during and following the breeding season, tracking them to presumed offshore foraging habitats in the south Atlantic Ocean. Leatherback turtles spent 100% of their time during the breeding period within the Exclusive Economic Zone (EEZ) of Equatorial Guinea, with a core distribution focused on the south of Bioko Island extending up to 10 km from the coast. During this period, turtles spent less than 10% of time within the existing protected area. Extending the border of this area by 3 km offshore would lead to a greater than threefold increase in coverage of turtle distribution (29.8 ± 19.0% of time), while an expansion to 15 km offshore would provide spatial coverage for more than 50% of tracking time. Post-nesting movements traversed the territorial waters of Sao Tome and Principe (6.4%of tracking time), Brazil (0.85%), Ascension (1.8%), and Saint Helena (0.75%). The majority (70%) of tracking time was spent in areas beyond national jurisdiction (i.e. the High Seas). This study reveals that conservation benefits could be achieved by expanding existing protected areas stretching from the Bioko coastal zone, and suggests shared migratory routes and foraging space between the Bioko population and other leatherback turtle rookeries in this region.