Aim: Essential habitats are areas that support biological and ecological functions critical for species' survival. For highly mobile and elusive marine species, aggregations in these habitats provide rare opportunities to study their ecology and inform conservation. We aimed to build a dynamic species distribution model (SDM) to predict essential habitats for migratory marine species. The model was tested on whale sharks (Rhincodon typus), a species with similar to 30 documented aggregation sites across their global distribution, addressing a major knowledge gap in the southwest Pacific (SWP). Location: Coral Sea, southwest Pacific. Methods: High-resolution, movement-informed SDMs were built using behaviourally filtered juvenile whale shark satellite tracks (low move-persistence locations) to quantify key environmental drivers of inferred foraging and predict dynamic suitability of essential habitat in the SWP. An ensemble modelling approach was applied to account for model uncertainty and improve model reliability by combining regression and machine learning algorithms. Results: Model predictions indicated high suitability in the northern Great Barrier Reef during the monsoon season (November-April), shifting eastward into the Coral Sea and beyond during the dry season (May-October). Bathymetric variables (depth, distance to deepwater drop-off) were key drivers of occurrence, while dynamic variables like sea surface temperature and productivity proxies also contributed largely to model predictions. Across algorithms, spatial block cross-validation and external validation with independent sightings indicated moderate but consistent discriminatory ability. Habitat suitability predictions varied across algorithms, underscoring the advantages of integrating diverse modelling approaches. Main Conclusions: This study presents the first movement-informed predictions of essential habitat suitability for juvenile whale sharks in the SWP, providing a framework for improving population assessments and guiding research and management. The dynamic SDM approach is broadly applicable, facilitating essential habitat identification, research prioritisation in data-limited regions, and targeted conservation in dynamic marine environments.

Despite the increased international attention to whale shark conservation, their populations remain predominantly depleted due to anthropogenic activities such as fishing, ship collisions, and marine pollution. Reports of whale shark strandings in Indonesia have been increasing in recent years, elevating concerns regarding their well-being and the potential disturbance to their population recovery. However, limited understanding of stranding patterns, trends, and the oceanographic factors potentially driving these events has resulted in efforts focusing primarily on responding to strandings rather than implementing effective mitigation strategies. Using a 13-year stranding dataset (n = 115) obtained from open-access databases, reports, news, and publications, we examined the characteristics of stranding cases in Indonesia, including population demographics, where hotspots occur, and whether their occurrence is related to oceanographic dynamics in the region. Our study highlights significant population-level disturbances, with 70% of stranded individuals being large juveniles (4–7 m). It also documented a positive interannual trend in stranding cases (R² = 0.67, p < 0.01). The southern coast of Java has emerged as a stranding hotspot, with events seasonally associated with strong upwelling, likely related to the seasonal foraging activities of whale sharks in the region. Although natural events were identified as the main factors contributing to whale shark strandings, anthropogenic activities may also play an important role and require further investigation.

Biologging devices have revolutionised our understanding of aquatic animal movement by enabling the collection of detailed depth and temperature time-series. The advent of pop-up satellite archival tags has been particularly impactful, facilitating the collection of tens of thousands of depth time-series (DTS) datasets, with deployment periods ranging from days to years. Datasets from recovered tags are more detailed than those transmitted via satellite, yet both are commonly reported with rudimentary histograms of time-at-temperature and time-at-depth. Such histograms often fail to capture the complex temporal dynamics of vertical movements that are available from the high sampling frequency time-series in recovered tags. This study describes a robust and effective methodological workflow for the quantitative analysis of large DTS datasets collected from archival tags deployed on gill-breathing aquatic animals, utilising continuous wavelet transformation (CWT), Principal Component Analysis (PCA), and k-means clustering. CWT was employed to detect key periodic patterns within the data. Daily wavelet components were calculated across different wavelet periods (e.g., 5-min through 24-h) and reduced via PCA to characterise daily vertical movement behaviour while preserving variance. Finally, unsupervised k-means clustering was used to classify vertical movement behaviours according to their wavelet components and depth summary statistics. This approach efficiently processed large quantities of data, and validation using simulated data demonstrated its robustness and versatility, with assigned behaviour clusters matching the original simulated behaviour types with high consistency (97.7%). For the empirical data, distinct behavioural clusters were identified across a wide range of species, including an oceanic manta ray Mobula birostris, whale shark Rhincodon typus, Atlantic cod Gadus morhua, and largetooth sawfish Pristis pristis. Down sampling of the DTS revealed the workflow to be somewhat insensitive to the sampling frequency of tags, maintaining 83.9% consistency as sampling frequency decreased from one to 15-minutes. These results not only underscore the workflow’s efficacy but also highlight its broad applicability in diverse settings. To facilitate uptake of this approach, an R package FishDiveR, tailored for the implementation of this analytical methodological workflow has been developed.

The Raja Ampat epaulette shark (Hemiscyllium freycineti) is an endemic species inhabiting shallow coastal habitats of the Raja Ampat Archipelago, Indonesia. Despite recent legal protection, information on its biology, population structure, and spatial ecology remains limited, constraining effective conservation. To address these gaps, a total of 64 nocturnal surveys (averaging 1.8–2.3 hours each) were conducted between February 2024 and April 2025 at six sites in the Dampier Strait region. Using photo-identification and passive integrated transponder tagging, 736 unique individuals were identified from 1,191 sightings, with most records from Arborek Island (n = 602). Of these, the population comprised 415 females and 321 males, resulting in a significantly female-biased sex ratio. Total length (TL) ranged from 19.4 to 75.0 cm (mean = 51.1 cm), and body mass ranged from 24 to 1,025 g (mean = 412.8 g). The length–weight relationships indicated negative allometric growth in both females (b = 2.91) and males (b = 2.81). Estimated length-at-maturity was 56.59 cm TL for females and 56.42 cm TL for males, with no significant difference between sexes. Relative density ranged from 333 to 2,462 individuals per km², representing the highest population density recorded globally for Hemiscyllium. A total of 256 individuals were resighted at least once, with resighting intervals extending up to 451 days. Immature individuals exhibited significantly higher growth rates than mature ones (7.8 vs 2.8 cm year-1), while no sex-specific difference in growth was detected. The best-supported and biologically meaningful growth model, seasonally oscillating ELEFAN with simulated annealing, estimated an asymptotic length (L∞) of 79.6 cm for all individuals, with a growth coefficient (K) of 0.747 year-1. Growth showed pronounced seasonal oscillations (C = 0.915). Sharks were most frequently observed in seagrass meadows. Habitat use analyses revealed ontogenetic partitioning. Coral reefs appear to function as a nursery habitat with 69% immature sharks, while seagrass and sand habitats supported higher proportions of adults. Individuals were highly resident, showed no inter-site movement, and occupied small spatial ranges, with maximum net displacements of 475 m. Collectively, these findings provide the first demographic and spatial baseline for H. freycineti in Raja Ampat.

Abstract Background Biologging and telemetry have transformed our understanding of marine megafauna movement ecology. Yet, methodological constraints continue to limit data quality and deployment duration. Devices recording whale shark (Rhincodon typus) behaviours and movements have been used for decades, but they remain challenging to deploy and vary in success. Recently, spring-loaded clamp-based systems have emerged as one of the most widely used approaches to attach electronic tags to the fins of this globally endangered species. Currently, however, no consensus guidelines exist as to how to optimise this approach, potentially leading to continued underperforming deployments limiting analysis potential. Here, we synthesise experiences with clamp-based tagging worldwide through a targeted survey of whale shark researchers. We explore performance and challenges with a view to propose current best practices in the field. Results Whale shark researcher responses to the survey highlighted clamp-based systems as a practical and more widely applicable approach than drill-based methods, which are often used to secure tags to other large sharks. They also noted that clamps have greater retention potential and are suitable for a wider range of tags compared to dart-based methods, but are still constrained by design, placement, and deployment conditions. Researchers used a variety of materials and designs to build their own clamps, often facilitated by direct collaboration with each other or key manufacturers. Clamps produced highly variable outcomes, ranging from successful long-term satellite transmissions over 200 days and short-term biologging for 48 h at 20 Hz, to premature detachment and cases of fin damage. For long-term clamps, changes in position on the fin allowed for more stable satellite transmissions over time. Some clamp designs achieved data quantity and quality close to that of drilled deployments, demonstrating their potential to rival traditional methods while offering a less invasive approach. Results emphasised the ongoing need for technological refinement and rigorous evaluation of clamp performance and associated impacts. Conclusions Based on collective insights, we present a unified approach to clamp design and positioning, and identify key priorities for advancing this attachment technology, such as aiming for positions b-2 and c-2 on the fin and ensuring the clamp bridge distance (always between 30 and 50 mm) and tension are matched to shark size. Optimising clamp systems could substantially improve our ability to generate high-quality, long-duration movement data while minimising tagging impacts on the animal where possible. This could enhance ecological and conservation research outcomes for endangered whale sharks, with broader implications for tagging other large-bodied marine megafauna.

Whale sharks (Rhincodon typus) predominantly inhabit the epipelagic layer, yet dives to at least 1928 m have been reported. Even so, current understanding of the species’ true maximum dive depth is constrained by the technological limitations of depth sensors of commercially available satellite tags, which are generally rated to a maximum depth of 2000 m. Here, we report a new maximum depth range of 1978–2527 m inferred from a Wildlife Computers custom-calibrated SPLASH10-346C finmount tag (2500 m capability), deployed on a 7 m juvenile male whale shark in the Coral Sea, Australia. This extends the currently accepted depth limit by 50–599 m.

ABSTRACT Environmental DNA (eDNA) metabarcoding is a powerful tool for monitoring elusive marine species, but its effectiveness is constrained by incomplete reference databases. This limitation is especially evident for epaulette sharks (Hemiscyllium), a genus of small benthic sharks endemic to the Indo‐Australian Archipelago. Six of the nine species occur in eastern Indonesia and are fully protected under national law, yet monitoring their distribution remains challenging using traditional methods. To address this gap, we developed the first genus‐specific eDNA metabarcoding assay for Hemiscyllium, targeting the mitochondrial NADH4 gene. Laboratory validation confirmed that the new ES‐200ND4 primer amplified Hemiscyllium DNA in simulated eDNA experiments, even at low concentrations (< 11 ng/μL). Field application in Raja Ampat detected the endemic H. freycineti at six of the seven sampling locations. The ES‐200ND4 primer demonstrated taxonomic specificity, with all 55 ASVs generated from field samples assigned exclusively to H. freycineti (mean genetic distance: 0.78%), while the universal 12S marker (elas02) exhibited non‐specific amplification but detected a broader range of marine taxa, including H. freycineti (17 ASVs), Carcharhinus sp. (1 ASV), and numerous phytoplankton groups. Notably, eDNA detection at Dayan, where daytime visual surveys recorded no sharks, underscores the method's capacity to reveal species presence when traditional approaches fall short. Overall, this study presents the first genus‐specific eDNA metabarcoding assay for Hemiscyllium spp. and the first application of NADH4 as a metabarcoding marker in marine environments. Finally, this scalable assay supports Indonesia's protective legislation for Hemiscyllium and offers a transferable framework for monitoring other data‐limited, cryptic, or threatened marine taxa.

The reef manta ray (Mobula alfredi) is a highly mobile pelagic marine ray found throughout the tropical and subtropical waters of the Indo-Pacific, but investigation into their behavior and ecology within Papua New Guinea has not been previously undertaken. Furthermore, the home range, dispersal characteristics, and inter-seasonal fine-scale habitat use of this species is limited. To address these data gaps and investigate the vertical and horizontal habitat use of a previously unstudied population, SPLASH10-F-321A pop-off archival satellite tags were used to track ten adult individuals from 4-181 days between 2016-2018 across two distinct monsoonal periods in the Samarai Islands of Milne Bay, southeastern Papua New Guinea. Our findings indicate strong site-attached movement patterns for reef manta rays in this region, with 75% of relocations occurring within ten kilometers of the tagging site. While occasional movements beyond this range were observed, the maximum displacement distance was 86.9 km, and no consistent seasonal differences in horizontal displacement distance were detected. Tagged rays displayed a clear preference for the Samarai Islands and the Papuan Plateau across both monsoons, with shallow bathymetry and elevated chlorophyll-a values driving observed habitat preferences. We found evidence for shifts in vertical occupancy of the water column that corresponded with the mixed layer depth; dives were deeper when the mixed layer depth was shallow, suggesting that reef manta rays can exhibit behaviorally plastic responses to seasonal variations in oceanographic conditions. These findings provide the first insight into the movement ecology of this reef manta ray population that can be used to inform the development of economically valuable manta ray tourism practices and a sustainable management plan in the region.

The whale shark (Rhincodon typus) is an iconic species in the Bird’s Head Seascape (BHS) in eastern Indonesia, yet little is known about its population and residency patterns across the region. This study documents the population demographics of this globally Endangered species from four key regions within the BHS: Cenderawasih Bay (CB), Kaimana (KA), Raja Ampat, and Fakfak. Using 13 years of photographic identification (photo-ID) data sourced from researchers and citizen scientists, we aim to provide a better understanding of population dynamics, residency patterns, and threats to the species. From September 2010 to October 2023, a total of 1,118 sightings of 268 different individuals were recorded, almost exclusively around lift-net fishing platforms (bagans). The population was strongly male-biased (8.8:1.0), with estimated total lengths ranging from 2 to 8 m, and most individuals in the 4–5 m size class, indicating a dominance of juvenile males. Over half (52.6%) of the individuals were re-sighted at least once, with one re-sighting span lasting 10.63 years. Most sightings (97.8%) were concentrated in CB (551 sightings, 159 individuals) and KA (542 sightings, 95 individuals). Only two individuals were seen in multiple regions, suggesting limited movement and potential habitat segregation. Lagged Identification Rates showed substantially higher residency in CB (77.1 days ± 34.4 SE) than in KA (37.8 days ± 9.7 SE). Scarring was recorded in 76.9% of individuals, with minor abrasions (47.4%) and fin nicks (39.9%) being the most common, followed by amputations (15.3%) and lacerations (14.2%). Only 2.4% of scars were likely inflicted by boat propellers, and only 3.4% of injuries were recorded as bites by predators. KA had a higher proportion of scarred sharks (83.7%) compared to CB (73.7%). The long-term presence and high re-sighting rates of juvenile whale sharks in CB and KA highlight their importance as key habitats within the BHS. While most sightings of whale sharks in the BHS occurred inside marine protected areas, the relatively high percentage of individuals with injuries apparently related to negative interactions with fisheries and tourism underscore the need for improved management to ensure the well-being of this fully protected species in Indonesia.

Coelacanths are arguably one of the most emblematic and evolutionarily-important of the marine vertebrates. To date, only two species are known globally: the West Indian Ocean Coelacanth, Latimeria chalumnae, found in the Mozambique Channel, from Southern Africa to Comoro Islands, and the Sulawesi Coelacanth, L. menadoensis, found off Sulawesi and Western New Guinea in Indonesia. The latter species has been much less documented than its African congener, and due to the difficulty of reaching the deep-reef habitats it lives in, very few in situ observations were made, and only from submersibles or Remotely Operated Vehicles. We report here the first observations of an adult coelacanth in the North Maluku Province of Indonesia and the first in situ images taken by divers of an Indonesian coelacanth, after successfully identifying suitable ecosystems during previous deep technical dives. This discovery contributes to our understanding of the biogeography and ecology of this vulnerable species and provides additional insights about its natural behaviour. Ultimately, we expect this work to help addressing coelacanth conservation in Indonesia, in an international context of dramatic biodiversity decline and natural ecosystems destruction.

Cryptobenthic reef fishes (CRF), although the smallest vertebrates on coral reefs, account for approximately 40% of fish species and nearly 50% of fish abundance within these ecosystems. Their diversity can be attributed to their extremely limited dispersal abilities and short generation times, which promote allopatric speciation, along with their ability to partition microhabitats at a very fine scale. Notably, the small size, cryptic nature, and conserved morphology of some CRF groups have contributed to the presence of many undetected cryptic species, which may require a genome-wide species delimitation approach to discern how many species are present. In particular, the genus Eviota is one of the most species-rich groups, with 133 species described to date. It ranges from the Red Sea to Hawaii and French Polynesia and is known to comprise numerous cryptic species. Here, we conducted an integrative species delimitation study of the Eviota sigillata species complex, which includes two nominal species described based on morphological characters; however preliminary genetic data suggest the presence of multiple cryptic lineages. We used molecular data from mitochondrial DNA and genome-wide SNP data generated via double digest restriction site associated sequencing (ddRADseq), in combination with morphological data to infer the number of species in the E. sigillata species complex. Specifically, we estimated phylogenetic trees, conducted several types of single-locus and multilocus species delimitation analyses, and compared these to groupings based on morphology and geographic distribution. Collectively we found evidence for the presence of 9-13 lineages within the E. sigillata species complex, with genetic lineages corresponding well with the biogeographic history of the group. Our results support the existence of at least nine species. We further confirmed that the original morphological diagnostic characters used for the taxonomic identification of the two nominal species were not useful for distinguishing each of the nine clades in the complex, but may be helpful in diagnosing groups of closely-related species. Overall, our study sheds light onto the patterns of speciation within CRF and provides a glimpse of the tremendous hidden diversity that still remains to be discovered in coral reef fishes.

The reproductive biology of the whale shark (Rhincodon typus), the world’s largest fish, remains poorly understood, in large part due to the rarity of observations of neonates and of breeding behaviours. Although several regions in Indonesia, including Saleh Bay (West Nusa Tenggara Province), have been identified as aggregation and sighting sites for juvenile whale sharks (2–7 m total length, TL), smaller individuals from these potential nursery areas have not been previously documented. In August 2024, fishermen operating lift-net fishing vessels (bagans) in eastern Saleh Bay reported five separate sightings of a small whale shark estimated at 1.2–1.5 m TL and approximately four months old. Subsequently, on 6 September 2024, a male neonate measuring approximately 135–145 cm TL, estimated to be around four months old, was incidentally caught inside a bagan lift-net. These observations represent the first records of neonatal whale sharks in Indonesia and among the smallest free-swimming individuals ever documented globally, and suggest that Saleh Bay may serve as a pupping and early nursery area for whale sharks. These findings highlight the ecological significance of Saleh Bay for the early life stages of whale sharks and underscore the importance of collaborative monitoring and citizen science involving bagan fishermen in advancing the research and conservation of this endangered species.

Deep dives are performed by a range of marine megafauna, yet their function remains poorly understood. Proposed functions include foraging, predator avoidance, and navigation, but limited fine-scale data have hindered rigorous testing of these hypotheses. Here, depth time-series data from eight recovered and 16 non-recovered satellite tags deployed on oceanic manta rays (Mobula birostris) in Indonesia, Peru, and New Zealand were examined to characterise extreme dives and identify their potential function. From a total of 46,945 dives, 79 extreme dives (>500 m) were recorded, 11 of which were documented from recovered tags and associated high sampling frequency. Extreme dives were distinguished by rapid descents (up to 2.9 m s⁻¹), brief horizontal “steps” at depth, gradually slowing ascents, and extended periods spent near the surface both before and after diving. Unlike typical foraging dives, no substantial bottom phase was observed, and vertical oscillations—expected if feeding at depth—were absent. Extreme dives also occurred more frequently with increasing distance from the continental shelf edge as well as preceding periods of high 72h distance travelled, indicating they may inform subsequent movements. We propose that extreme dives enable oceanic manta rays to survey the properties of the water column, likely gathering environmental cues—such as temperature, dissolved oxygen, or geomagnetic gradients—to guide navigation and/or the decision to leave or remain in a general area. In open-ocean environments where external reference points are absent, such costly but infrequent dives may provide critical information for long-distance movements. Our results offer new insights into the role of extreme diving behaviour in oceanic manta rays and highlight the importance of fine-scale data for understanding deep-diving behaviours in marine megafauna.

A comprehensive understanding of cetacean ecology is crucial for conservation and management. In 2018, Kaimana was identified as an Important Marine Mammal Area (IMMA) due to the regular presence of feeding aggregations of Australian humpback dolphins (Sousa sahulensis), Pacific bottlenose dolphins (Tursiops aduncus) and Bryde's whales (Balaenoptera edeni). Despite this, information on cetacean ecology in the Kaimana region is currently lacking. Notably, no cetacean surveys have been undertaken in Kaimana since it was officially recognized as an IMMA. We monitored food-provisioning interactions between lift-net fisheries and cetaceans from May 2021 to March 2023 to examine cetacean sightings, abundance and feeding associations. Five species were positively identified, including a new record of Killer whales (Orcinus orca). Our findings suggest a strong association between T. aduncus and lift-net fisheries, where they have been observed feeding on anchovies from outside the net in the morning. While other species were also observed, their presence was less frequent. Furthermore, year-round sightings of S. sahulensis, B. edeni, and T. aduncus during the study period indicate that these species are resident in this region. Our results suggest that Kaimana fulfills a second IMMA sub-criterion (small and resident populations of these three species) that was not previously noted in the original IMMA assessment.

Indonesia is home to significant populations of globally vulnerable reef manta rays (Mobula alfredi) in at least four key regions: Berau, Nusa Penida, Komodo, and Raja Ampat. Despite detailed population studies in each of these regions, little is known about their horizontal movement patterns. Our study used satellite telemetry to investigate reef manta rays’ habitat use and home ranges. A total of 33 manta rays were tagged with SPLASH10F-321A satellite tags across the four regions: Berau (n = 5), Nusa Penida (n = 8), Komodo (n = 6), and Raja Ampat (n = 14), yielding usable data from 25 tags. The rays were tracked for 7 to 118 days (mean ± SD = 50 ± 30) from July 2014 to July 2022. The results showed localized movements, strong residency near tagging sites, and high site fidelity as evidenced by area-restricted search (ARS) behaviors and frequent revisitations. Most manta rays showed restricted home ranges in each region, with no connectivity between regions. Across 25 individuals, the home range (95% utilization distributions) varied significantly, ranging from 19 to 48,294 km2 (mean ± SD = 4667 ± 10,354). These findings offer important insights into the spatial movement patterns of reef manta rays in Indonesia, allowing the formulation of more effective management strategies.

Aggregations are key events, supporting critical ecological and biological functions in many species. For highly mobile and elusive species, aggregations often provide the only feasible opportunities for research. Whale sharks (Rhincodon typus) form at least 30 consistent seasonal aggregation sites globally, yet none have been documented in the Coral Sea, despite sporadic sightings of solitary individuals and groups. This study aimed to identify and characterise the first whale shark aggregation on Australia's east coast by predicting potential sites through a data layering approach and confirming their presence through targeted field expeditions. A combination of historical sightings data, expert and anecdotal knowledge, and scientific knowledge from other whale shark aggregation sites led to the identification of Wreck Bay, situated at the far northern Great Barrier Reef, as potential aggregation habitat. An initial field expedition in 2019 confirmed the aggregation, and three subsequent voyages in 2021-2024 gathered further demographic and movement data. A total of 59 individuals were identified, with a strong male bias (3.5:1) and all classified as immature sharks ranging from 3.5 to 8.0 m in estimated total length. Satellite tracking revealed a mean residence time of approximately 3 weeks (21.6 days ±10.1 SD; range: 7-43 days), with some individuals revisiting the aggregation in subsequent years. The peak aggregation period occurs from late November to late December, with movements concentrated along the continental shelf before dispersing into the Coral Sea. Tracked sharks (n = 18) exhibited wide-ranging movements, with a mean track duration of 144 days (range: 3-770 days) and a mean total track length of 1463 km (range: 19-11,355 km). This study provides the first evidence of a whale shark aggregation in the Coral Sea and highlights Wreck Bay as key habitat for this iconic and globally endangered species.

Understanding the movements and associated behaviours of animals is critical for informed management decisions. This is particularly important for species such as the Endangered oceanic manta ray (Mobula birostris), which has a conservative life history and is therefore vulnerable to population disturbances. Twelve oceanic manta rays were tracked for 9–84 days using high-resolution SPLASH10F-321A/E Fastloc GPS tags during their seasonal presence in northeastern Aotearoa, New Zealand, which indicated broad variation in fine-scale (100 m to 10 km) movements in Tīkapa Moana—Te Moananui-ā-Toi—the Hauraki Gulf and the nearby shelf. While in this region, the tagged oceanic manta rays spent most of their time in surface waters <5 m, with occasional dives up to 365 m. Generalized additive mixed-effect models indicate that movement patterns associated with daytime foraging in the region are linked to northerly winds but inhibited by high wind speeds (10+ ms−1). Dives deeper than 5 m were more frequent at night, and during gibbous moon phases. A key challenge of this study is the lack of knowledge about oceanic manta ray prey composition and distribution: gathering and incorporating this information into modelling is necessary to better understand the movement ecology and behaviours of manta rays at the southernmost part of their range.

The pelagic thresher shark ( Alopias pelagicus ) is globally endangered, threatened by bycatch, and targeted in industrial and artisanal fisheries in Indonesia. However, a lack of information about their ecology, particularly movement and habitat use, hinders the development of science-based conservation measures to protect the species. Here, we report our research, which is the first to use a combination of satellite and passive acoustic telemetry to investigate the movement and residency of the pelagic thresher shark within Indonesia's waters, especially in areas impacted by local fisheries. A total of 24 sharks were tagged with archival satellite tags ( n = 9), internal acoustic tags ( n = 10), and both tags ( n = 5) in Selat Pantar Marine Protected Area (MPA). The tagged sharks, dominated by females (71%) ranged in size from 125–180 cm FL (mean ± SD: 161 ± 13). Seven of the fifteen acoustically tagged sharks were detected by the receivers, while twelve of the fourteen satellite tags reported data. The satellite tags stayed attached for 81–181 days, and the acoustic tag detection periods ranged from 44–175 days. Horizontally, we found the satellite-tagged sharks moved broadly, mainly offshore, approximately 90 km from tagging locations. They moved to areas between Banda, Flores, and Savu Sea regions, where unregulated and unreported longline and gillnet fisheries are known to operate. Meanwhile, the acoustically tagged sharks showed distinct diel patterns around the Selat Pantar MPA's coastal waters, indicating potential philopatric behavior. Vertically, the sharks spent significantly ( p < 0.001) more time in deeper water during the day and moved to shallower water at night. The deepest dive recorded was 1,889.5 m, which is the deepest ever recorded from the species. Our results suggest that area-based protection can be an effective nearshore conservation tool as individuals appear to remain in relatively restricted areas within Selat Pantar MPA for extended periods. However, fisheries regulation aimed at restricting illegal longline and gillnet fishing is also necessary to protect sharks when they move offshore. Our findings have been communicated to the relevant governments, resulting in increased political will and new legislation to protect them within the Selat Pantar MPA and connected waters of East Nusa Tenggara.

The expansion of the world 's merchant fleet poses a great threat to the ocean 's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable species. The Endangered whale shark ( Rhincodon typus ) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These "constellation " sites are of significant ecological, socioeconomic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world ( >50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species.

Though a previous study in Sudan confirmed the existence of a living hybrid of an oceanic manta ray (Mobula birostris) and a reef manta ray (M. alfredi), courtship behaviors between the two closely related species have never been documented. Here we report the first observation of courtship behaviors between two male M. birostris and a female M. alfredi at a manta ray cleaning station on a shallow coral reef seamount in Misool, Raja Ampat, Indonesia. The observed courtship event lasted for approximately 45 min and involved one male oceanic manta actively chasing the mature reef manta female around the cleaning station and repeatedly bumping her on the left wing tip with his right cephalic lobe, while the second male continuously flanked the female to seemingly prevent her retreat from the cleaning station and potential evasion of the pursuing male. Notably, the female exhibited a rapid coloration change, likely indicative of courtship-related stress, transitioning from the striking pale hue she exhibited throughout the courtship activity to a normal chevron pattern once the males departed.