Reliable ecological data on cetaceans remain scarce along the West African coast, where limited survey capacity constrains conventional monitoring. In such data-poor contexts, Local Ecological Knowledge (LEK) from artisanal fishers offers a valuable complementary source of information on species occurrence, habitat use, and interactions with fisheries. This study examines how socio-demographic, cultural, and operational factors structure the distribution of LEK on cetaceans among Gabonese artisanal fishing communities. Between 2022 and 2024, 189 fishers were interviewed across five major coastal regions. Using Fisher's exact tests, Multiple Correspondence Analysis, and Hierarchical Ascendant Classification, we identified six distinct fisher profiles that differed markedly in LEK acquisition. Older, more experienced, and predominantly West African migrant fishers exhibited the highest levels of LEK, whereas younger urban Gabonese fishers, particularly from Libreville, showed lower ecological familiarity. Participatory mapping revealed that over 75% of reported fishing locations were concentrated within 20 km of the coast and 95% within 52 km, indicating a strong spatial concentration of artisanal fishing effort in nearshore waters. This pattern suggests a high potential for spatial overlap between fishing activity and coastal cetacean habitats, with implications for bycatch risk. Our findings demonstrate that LEK is unevenly distributed and shaped by socio-cultural heterogeneity and fishing intensity. Recognizing these differentiated knowledge profiles can improve the reliability of LEK-derived indicators and enhance their integration into national biodiversity monitoring, species distribution modelling, and participatory bycatch mitigation strategies. This research provides actionable insights for inclusive marine governance in Gabon, and other data-poor tropical coastal systems.

The Arabian Sea humpback whale (Megaptera novaeangliae; ASHW) is understood to be the only population of this species that does not undertake long-range seasonal migrations between high- and low-latitude waters. Until recently, understanding the movements and range of individual ASHWs has relied mainly on comparisons of dorsal fin and tail-fluke images archived in photo-identification catalogues and on observations made during small-vessel surveys off the coast of Oman since 2000. The ASHW population is classified as Endangered by the IUCN Red List of Threatened Species, with an estimated 82 individuals off Oman’s coast (95% CI: 60–111), and faces increasing anthropogenic threats throughout its known range. To better understand the spatial ecology of this population, 14 Argos-enabled satellite tags were attached to ASHW off the Arabian Sea coast of Oman between February 2014 and December 2017. Individuals were tracked for a total of 749 days (mean=53, SD = 42, range=18–163 days) producing 484 days of depth-use data (mean=44, SD = 26, range=15-87). Home ranges extended along the western Arabian Sea coastline of northern Yemen and southern Oman, with a core area in the Gulf of Masirah (Oman). Switching state-space models revealed predominant area restricted search behavior (associated with breeding and foraging behavior) over continental shelf areas, with transiting movements occurring further offshore. The widest-ranging individual (a female, tag longevity 120 days) completed a round trip across the Northwest Indian Ocean between the Gulf of Masirah and the Gulf of Mannar (India). The track of this animal, and others along the coast of Oman, revealed an overlapping relationship between ecological drivers related to habitat use, including foraging and breeding, with fishing and shipping activities. The findings demonstrate the unique ecology of ASHW compared to other humpback whale populations and underscores the need for national and international authorities to incorporate these results into management initiatives to safeguard this small and Endangered population.

Genetic studies have differentiated three subspecies of humpback whales: Megaptera novaeangliae novaeangliae in the North Atlantic, M. n. australis in the Southern Hemisphere and M. n. kuzira in the North Pacific. However, these analyses did not include samples from the Arabian Sea humpback whale population (ASHW). Historic, behavioural, and previously published genetic data suggested that ASHWs are a discrete, isolated and resident population. This study provides further evidence of genetic uniqueness of the ASHWs by comparing samples collected in Oman with the three existing humpback whale subspecies. The morphological and genetic data obtained in this study confirmed the identification of the type specimen for Megaptera indica from Iraq as a humpback whale, closely related to contemporary ASHWs. Genetic differentiation between ASHWs and other subspecies were found (Fst values 0.1213-0.2441 and φST values 0.0831-0.6470). Together with the multiple lines of evidence for reproductive and behavioural isolation of this unique humpback whale population that does not undertake seasonal latitudinal migrations as do all other populations, this genetic data support the recognition of a fourth subspecies, which would be named for the type specimen from Iraq: Megaptera novaeangliae indica. Anthropogenic threats to ASHWs and their habitat are severe and escalating and there is a risk of extirpation. Population abundance is low with no evidence of increasing over the past two decades. The genetic differentiation of ASHWs may have been driven by a range of interdependent biogeographical and ecological factors coupled with behavioural adaptations over a period of ~43,000-113,000 years. Regionally coordinated conservation action is urgently needed to preserve this population’s unique genetic diversity.

The global growth of marine traffic, among many growing anthropogenic threats, is of particular concern for marine mammals. Assessing the co-occurrence of marine traffic and cetacean distributions provide useful information for understanding the spatial extent and level of pressures and threats posed by vessels. Regional and local marine traffic is increasing within the territorial waters of Reunion Island, included in the Mascarenes Important Marine Mammal Area. This study provides the first description of the spatial distribution of vessels within these waters using Automatic Identification System (AIS) data and provides an assessment of the pressures and threats vessels may pose to five cetacean species (the spinner dolphin, the Indo-Pacific bottlenose dolphin, the common bottlenose dolphin, the pantropical spotted dolphin and the humpback whale). We found that vessels occurred in all Reunion waters and identified two highly-used shipping corridors on either side of the island. Our results highlighted areas of potential threats from marine traffic for each of the five species. These areas mostly mirrored their preferential core habitats, which raises concerns, especially for the resident and most vulnerable species. Given the increase in marine traffic in the western Indian Ocean region, this study provides additional information in support of an ongoing French initiative to implement an "Area to Be Avoided" in Reunion waters, in order to improve safety and security while also benefiting to cetacean conservation.

In 1883 a baleen whale stranded at ‘baie de Bassora’ (Basrah Bay), in the Chat-el-Arab river delta, Iraq, at the northwestern corner of the Persian/Arabian Gulf. Gervais obtained the complete specimen for the national museum in Paris (MNHN), and described it as a new humpback whale species Megaptera indica H.-P. Gervais, 1883. The authors studied the incomplete and slightly damaged holotype skull, measured and estimated craniometrics, and concluded that M. indica is a junior synonym of Megaptera novaeangliae (Borowski, 1781). No postcranial bones were found. Importantly, two cranial features suggest that M. indica nests between Atlantic humpback whales and other large Balaenopteridae. Megaptera novaeangliae has the widest skull index, i.e. breadth skull at squamosals relative to condylobasal length (57–66.9%, n=8), higher than M. indica which scored 54.9%, and considerably higher than other Balaenopteridae. Also the ratio of the width of skull at postorbitals (frontale) versus rostrum width at base in M. indica is smaller and barely overlaps with Atlantic humpback whales (n=4), again suggesting taxonomic significance. Gervais also reported several postcranial differences, presently unverifiably. Cranial findings support subspecific status, Megaptera novaeangliae indica (H.-P. Gervais, 1883), proposed also by Amaral et al. (submitted) for the Arabian Sea (cum Persian/Arabian Gulf) humpback whale population, based on mtDNA control region analysis.The reported pachyostosis in the Iraqi whale is suggested a possible example of phenotypic plasticity, an adaptation to the unusually high-salinity, high-density habitat of the Gulf, as to reduce buoyancy and avoid insolation.

Arabian Sea humpback whales ( Megaptera novaeangliae ; ASHW) are listed as Endangered by the International Union for the Conservation of Nature (IUCN). The long-term presence and increased prevalence of tattoo skin disease-like (TSD-L) dermatopathy is a concern for this small non-migratory population. Characterized by irregular or rounded, light gray or whitish cutaneous lesions, this condition resembles tattoo skin disease, caused by cetacean poxviruses. Although the etiological agent and pathogenicity of TSD-L dermatopathy are unknown, previous studies have suggested that it is an indicator of population health. Until now, disease diagnosis had been based on photographs collected from survey vessels. In this study, we describe a novel method of identifying and quantifying TSD-L lesions in ASHW, using drone aerial photography. Aerial photos of the entire dorsum were selected for 18 whales with the same criteria applied for assessing body condition to quantify the percent coverage for each individual. We effectively diagnosed this condition from close-up aerial photos or good-quality photos of the lateral body surface taken from the research vessel in 13 whales. TSD-L dermatopathy coverage ranged from 2.34 to 57.00% and measurements were consistent between photographs of the same whale (SD = 1.86%). Drone aerial photography provided a useful and complimentary approach to identify and quantify TSD-L lesions. Continued monitoring using this non-invasive method should be combined with other population and health monitoring tools to increase our understanding of the characteristics and epidemiology of this condition, and to provide critical information for conservation efforts that ensure the recovery of this endangered population.

The 20th century commercial whaling industry severely reduced populations of great whales throughout the Southern Hemisphere. The effect of this exploitation on genetic diversity and population structure remains largely undescribed. Here, we compare pre- and post-whaling diversity of mitochondrial DNA (mtDNA) control region sequences for 3 great whales in the South Atlantic, such as the blue, humpback, and fin whale. Pre-whaling diversity is described from mtDNA extracted from bones collected near abandoned whaling stations, primarily from the South Atlantic island of South Georgia. These bones are known to represent the first stage of 20th century whaling and thus pre-whaling diversity of these populations. Post-whaling diversity is described from previously published studies reporting large-scale sampling of living whales in the Southern Hemisphere. Despite relatively high levels of surviving genetic diversity in the post-whaling populations, we found evidence of a probable loss of mtDNA lineages in all 3 species. This is evidenced by the detection of a large number of haplotypes found in the pre-whaling samples that are not present in the post-whaling samples. A rarefaction analysis further supports a loss of haplotypes in the South Atlantic humpback and Antarctic blue whale populations. The bones from former whaling stations in the South Atlantic represent a remarkable molecular archive for further investigation of the decline and ongoing recovery in the great whales of the Southern Hemisphere.

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2–3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.

The south-western Indian Ocean (SWIO) is a region of global importance for marine mammal biodiversity, but our understanding of most of the species and populations found there is still rudimentary. The Indian Ocean Network for Cetacean Research (IndoCet) was formed in 2014 and is dedicated to the research of all cetacean species across the SWIO. Since 2019, there have been efforts to create a regional network for coordinated response to stranding events as well as training and capacity building in the SWIO region. The present analysis represents a first investigation of stranding data collected by various members and collaborators within the IndoCet network, covering over 14,800km of coastline belonging to nine countries/territories. Between 2000-2020, there were 397 stranding events, representing 1,232 individual animals, 17 genera and 27 species, belonging to six families: four balaenopterids, one balaenid, one physeterid, two kogiids, six ziphiids and 14 delphinids. Seven mass strandings were recorded: two were composed of three to 20 individuals and five composed of >20 individuals. Spatial analysis of stranding events indicated that local spatio-temporal clusters (excessive number of events in time and geographic space) were present in all countries/territories, except for the Comoros. The only significant cluster was detected on the southwest coast of Mauritius, just west of the village of Souillac. The SWIO region predominantly comprises relatively poor countries/territories, but imminent Blue/Ocean economy developments are prevalent throughout the region. This study highlights the importance of establishing baselines upon which any future potential impact from anthropogenic developments in the region can be measured.

Assessing abundance and monitoring ecology and population trends are of critical importance for animal species of conservation concern. For sea turtles, annual nest counts represent the most common method of estimating population size. However, to develop a better understanding of population trends, these data need to be complemented by other reproductive parameters, which are lacking for many nesting populations across central Africa.To this end, an intensive capture-mark-recapture programme was conducted spanning 21 years (1997-2018) in the most important nesting sites on the Atlantic coast of central Africa (Gabon and Congo) for leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) sea turtles.A total of 18,105 encounters of 14,109 D. coriacea individuals and 2678 encounters of 2427 L. olivacea individuals were recorded. Biological and technical parameters such as clutch frequency, inter-nesting interval, remigration interval, annual survival rate, somatic growth, size trends, tag loss and number of annual nesting females were estimated through a variety of methods and models.The study detected a decline in body size and low survival probability (not due to tag loss) in both species but no clear decline in estimated annual number of nesting females. High fidelity to nesting sites (<30 km for both species) implies that the current conservation strategy, protecting the main nesting areas, could be effective.We recommend that local conservation managers promote: (i) continued monitoring of the nesting activity of the two species through capture-mark-recapture programmes; (ii) continued nest counts at long-term monitoring sites, which may also detect possible spatial shifts; and (iii) strengthening of cross-border cooperation between Gabon and Republic of the Congo given the observed connectivity between nesting sites of the two countries.

The photo-identification catalogue of humpback whale tail flukes from Oman was compared with those from Antongil Bay, Madagascar and study sites in South Africa and Mozambique collectively termed the ‘East African Mainland’. No matches were found, supporting other lines of evidence that the humpback whales studied off the coast of Oman form part of a discrete Arabian Sea population, which adheres to a Northern Hemisphere breeding cycle, and has little or no ongoing exchange with the nearest neighbouring populations in the southern Indian Ocean. While the sample size from Oman is small, and low levels of ongoing exchange might not be detected in this type of catalogue comparison, the study nonetheless emphasises the need to pursue research and conservation efforts in the known and suspected range of the Endangered Arabian Sea humpback whale population.

Small boat surveys were conducted between 2000 and 2003 in three main regions of Oman’s coastal waters: Muscat, the Gulf of Masirah and Dhofar. Survey data were analysed to calculate relative abundances of the seven most frequently encountered species in these areas. These include (in order of frequency) bottlenose dolphins (Tursiops sp.), long-beaked common dolphins (Delphinus capensis), humpback whales (Megaptera novaeangliae), spinner dolphins (Stenella longirostris), Indo-Pacific humpback dolphins (Sousa chinensis), Bryde’s whales (Balaenoptera sp.) and Risso’s dolphins (Grampus griseus). Other species observed include false killer whales (Pseudorca crassidens), blue whales (Balaenoptera musculus), rough-toothed dolphins (Steno bredanensis) and unidentified beaked whales. Encounter rates per distance searched were plotted by 0.1 x 0.1 degree grid cell, giving an indication of relative abundances and key areas of habitat used by each of the seven most frequently encountered species. These plots demonstrate that the nearshore areas of the Gulf of Masirah, as well as the coastal waters of Dhofar, are areas of concentration for the Arabian Sea’s recently designated Endangered subpopulation of humpback whales, as well as Indo-Pacific humpback dolphins, which are considered Near Threatened on the IUCN Red List of Threatened Species.1 The results presented here provide valuable baseline data for future research and help to inform conservation management efforts that are required to address the highly vulnerable status of the humpback whale and Indo-Pacific humpback dolphin populations in question.

Wild animals are captured or taken opportunistically, and the meat, body parts, and/or eggs are consumed for local subsistence or used for traditional purposes to some extent across most of the world, particularly in the tropics and subtropics. The consumption of aquatic animals is widespread, in some places has been sustained for millennia, and can be an important source of nutrition, income, and cultural identity to communities. Yet, economic opportunities to exploit wildlife at higher levels have led to unsustainable exploitation of some species. In the literature, there has been limited focus on the exploitation of aquatic non-fish animals for food and other purposes. Understanding the scope and potential threat of aquatic wild meat exploitation is an important first step toward appropriate inclusion on the international policy and conservation management agenda. Here, we conduct a review of the literature, and present an overview of the contemporary use of aquatic megafauna (cetaceans, sirenians, chelonians, and crocodylians) in the global tropics and subtropics, for species listed on the Appendices of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). We find that consumption of aquatic megafauna is widespread in coastal regions, although to varying degrees, and that some species are likely to be at risk from overexploitation, particularly riverine megafauna. Finally, we provide recommendations for CMS in the context of the mandate of the Aquatic Wild Meat Working Group.

The sub-population of humpback whales inhabiting the Arabian Sea is a small and genetically distinct population that remains in low latitudes year round. Designated as Endangered on the IUCN Red list of Threatened Species, the population faces a number of threats throughout its range, including entanglement in fishing gear, ship strikes, and habitat degradation. Research conducted primarily off the coast of Oman over the past 20 years has contributed to understanding the population’s distribution, abundance, and conservation status. However information on the population’s health and specific threats is limited. This study examines all available images of Arabian Sea humpback whales obtained between 2000 and 2018 for evidence of disease, predation, epizoites and human-induced scarring or injury to individuals. Tattoo-like skin disease was detected in 43.4% of 83 adult whales, with a roughly equal distribution between males and females. Prevalence of the disease was significantly higher in 2012-2018 (51.7%) than in 2000-2011 (24.1%). Killer whale tooth rakes were detected on the ventral surface of the tail flukes of 12% (95% CI 4.5-18%) of 77 individuals. Roughly two thirds (66.6%: 95% CI 52-80%) of the 42 individuals represented by good quality photos of the caudal peduncle region at the fluke insertion bore scarring patterns consistent with entanglement in fishing gear. Four individuals had injuries consistent with vessel strikes and at least two other individuals showed severe injuries and deformations likely caused by interactions with fishing gear. Documented entanglement events from Oman and Pakistan involved large-mesh nylon gillnets, known to be used extensively throughout the Arabian Sea. These findings indicate an urgent need to design effective management and mitigation of threats, and to continue monitoring Arabian Sea humpback whales, with an emphasis on methods that allow continued and expanded assessment of health, body condition, and anthropogenic interactions.

The Atlantic humpback dolphin (Sousa teuszii) is a critically endangered cetacean species endemic to coastal Atlantic waters of Africa. Its preference for shallow coastal habitat renders it vulnerable to incidental capture (bycatch) in non-selective fishing gears as well as to habitat degradation from all forms of coastal development. Although past and ongoing research has shed light on the distribution and conservation status of the species in a few locations, it is still poorly understood throughout most of the 19 countries in its 7000 km long range. From 2020 onward, international and regional collaboration to increase awareness and promote conservation action has intensified. These efforts, while in the early stages, exemplify the IUCN Species Survival Commission’s Assess-Plan-Act Conservation Cycle. While concrete conservation gains have not yet been achieved, efforts are being made to fill knowledge gaps and to broaden and motivate the network of international, regional, national, and local stakeholders that are actively engaged in marine and coastal conservation actions at multiple levels. The authors assess the strengths and weaknesses of the current approaches and identify elements that may be useful for other species with ranges spanning multiple countries where resources and capacity for conservation action are limited.

Monitoring how populations respond to sustained conservation measures is essential to detect changes in their population status and determine the effectiveness of any interventions. In the case of sea turtles, their populations are difficult to assess because of their complicated life histories. Ground-derived clutch counts are most often used as an index of population size for sea turtles; however, data are often incomplete with varying sampling intensity within and among sites and seasons. To address these issues, we: (1) develop a Bayesian statistical modelling framework that can be used to account for sampling uncertainties in a robust probabilistic manner within a given site and season; and (2) apply this to a previously unpublished long-term sea turtle dataset (n = 17 years) collated for the Republic of the Congo, which hosts two sympatrically nesting species of sea turtle (leatherback turtle [Dermochelys coriacea] and olive ridley turtle [Lepidochelys olivacea]). The results of this analysis suggest that leatherback turtle nesting levels dropped initially and then settled into quasi-cyclical levels of interannual variability, with an average of 573 (mean, 95% prediction interval: 554–626) clutches laid annually between 2012 and 2017. In contrast, nesting abundance for olive ridley turtles has increased more recently, with an average of 1,087 (mean, 95% prediction interval: 1,057–1,153) clutches laid annually between 2012 and 2017. These findings highlight the regional and global importance of this rookery with the Republic of the Congo, hosting the second largest documented populations of olive ridley and the third largest for leatherback turtles in Central Africa; and the fourth largest non-arribada olive ridley rookery globally. Furthermore, whilst the results show that Congo’s single marine and coastal national park provides protection for over half of sea turtle clutches laid in the country, there is scope for further protection along the coast. Although large parts of the African coastline remain to be adequately monitored, the modelling approach used here will be invaluable to inform future status assessments for sea turtles given that most datasets are temporally and spatially fragmented.

Abstract As part of the Post‐2020 Biodiversity Framework, nations are assessing progress over the past decade in addressing the underlying drivers that influence direct pressures on biodiversity and formulating new policies and strategies for the decade to come. For marine conservation, global marine protected area (MPA) coverage is still falling short of the 10% target set in 2010. Here we show that while this reflects a lack of progress in many low‐ and middle‐income countries, a few of these nations have met or exceeded international commitments. To provide an in‐depth explanation of how this was achieved in Gabon, we summarize the lessons learnt by our consortium of policy makers and practitioners who helped implement a comprehensive and ecologically representative network of 20 MPAs. We show the importance of creating a national framework, building long‐term stakeholder support, and focusing on research that guides implementation and policy; and outline a four‐step approach that countries and donors could use as an example to help meet international commitments. By responding to calls to share lessons learned to inform future Convention on Biological Diversity targets, we show how Gabon's experiences could inform change elsewhere.

In the marine environment, where there are few physical boundaries to gene flow, there is often nevertheless intraspecific diversity with consequences for effective conservation and management. Here, we compare two closely related dolphin species with a shared distribution in the Indian Ocean (IO) to better understand the biogeographic drivers of their population structure.