Metrics details Tiger sharks are apex predators with a circumglobal tropical and warm-temperate distribution with a general lack of population data for the central Indian Ocean tiger sharks display frequent use of the harbour area and reproductive characteristics of the world’s largest known tiger shark aggregation in a geographically-restricted area photo identification and laser photogrammetry we identified 239 individual tiger sharks over a 7-year study period The aggregation was female-dominated (84.5%) with both large juveniles and adults present Adult females were resighted over the entire study period displaying strong inter- and intra-annual site fidelity Modelled residency using maximum likelihood methods suggests they spent 60.7 ± S.E shorter residence periods and longer absence periods compared to juvenile females Prolonged abdominal distensions of adult females indicate they likely stay near Fuvahmulah during gestation and reproduce biennially Fuvahmulah seems to provide suitable conditions for gestation given the year-round provision of food and warm waters exhibited by strong site fidelity and temporal residency Our results show indications of a thriving population within the confines of protected waters Location of Fuvahmulah within the Maldives Archipelago in the Indian Ocean. The dive sites, where tiger sharks are frequently spotted and where most footage originates from, are marked in the map (Map was created using QGIS 3.28.1-Firenze, URL: https://qgis.org/download/) With a lack of data throughout the rest of the Indo-Pacific and the possibility of localised populations the reproductive cycle length remains unclear particularly for tiger sharks in the Maldives this study represents the first extensive investigation of the species with this method this study presents the first scientific description of this tiger shark aggregation with implications for the management and conservation of tiger sharks in the Maldives Between Dec 7th 2016 and Sep 30th 2023, we collected footage from a total of 788 separate dive surveys: 772 at the Tiger Harbor (TH) dive site, six at Farikede (FK) and ten from Offshore Plateau (OP) (Fig. 1) We saved 32,495 photographs and frame grabs from video material of sufficient quality to identify individual sharks (a) Countershading delineation in six different tiger sharks F-025) display intraspecific variation of the countershading delineation anterior to the pectoral fins This feature was most useful in differentiating the individuals (b) Cumulative number of identifications of tiger sharks by sex per month visiting tiger harbour The orange line indicates the cumulative number of dive surveys per month visual size estimates were assumed to be sufficient for approximate TL estimation of the tiger sharks Total length (TL) of visual size estimates from 213 sharks incremented by 0.5 m All females 3.5 m and larger were considered adults (a) Standardised width of presumably pregnant sharks over time Day 0 indicates the last measurement before the sharks’ absence period where we presume parturition may take place Sharks scored 1 or 0 were visually assessed as ‘pregnant’ or ‘not pregnant’ while ‘not scored’ refers to a shark’s appearance where we did not infer pregnancies based on their visual appearance (see Methods for more details) (b) An example of one individual’s presumed pregnancy (F-049) Number in brackets provides a corresponding day value to a) The standardised width of this shark increased until day 0 followed by a period of absence for 93d the standardised width of this shark had significantly declined Two consecutive pregnancies were recorded for nine individuals and three consecutive pregnancies were recorded for three individuals Consecutive periods of gestation and parturition were not significantly different from an expected two-year period (Chi-squared test Footage of pregnant sharks was separated on average by 788.7 (SD = 69.0) days or 2.16 years The residency models were run for (i) the entire population, (ii) adult females, and (iii) juvenile females. Model H, which included parameters for emigration, reimmigration and mortality of tiger sharks, had the lowest QAIC indicating the best fit for the data of all three data sets (Table 1) overall tiger sharks spent a mean of 65.5 ± S.E 76.1 [95%CI (55.5–79.4)] days in Fuvahmulah and a mean of 107.9 ± S.E Aggregation size was estimated to be 43.1 ± S.E 3.3 [95%CI (37.2–50.4)] individuals present in the study area on any given day adult female tiger sharks spent a mean of 60.7 ± S.E 7.5 [95% CI (50.2–72.9)] days in Fuvahmulah and a mean of 110.4 ± S.E Aggregation size was estimated to be 25.9 ± S.E 2.2 [95% CI (22.0–30.5)] individuals present in the study area on any given day juvenile female tiger sharks spent a mean of 93.0 ± S.E 42.7 [95% CI (32.7–182.1)] days in Fuvahmulah and a mean of 76.9 ± S.E whereas the aggregation size was estimated to be 16.0 ± S.E 2.1 [95% CI (12.0–20.2)] individuals present in the study area on any given day juvenile females spent shorter time periods away from the study site than adults while remaining for longer periods when present Their overall aggregation size was also considerably lower which is consistent with the amount of juveniles vs The results for all tiger sharks was similar to the results for the adult females except for aggregation size mean ± S.E.) for all tiger sharks (top panel) and for juvenile (red) and adult (blue) female tiger sharks visiting Fuvahmulah Model H (pale lines) is represented in all cases including emigration reimmigration and mortality as model presets The LIR plot for juvenile females showed high probability of resighting from day 1 to 6 days. LIR remained high until 687 days, or 1.9 years. After 2,158 days the LIR reached zero, implying permanent emigration or mortality (Fig. 5) most juveniles have not been identified for periods longer than three years The LIR plot for adult females displayed a rapid decline from day 1 to 189 days Afterwards the model curve stabilised at a value of 0.014 the LIR increased significantly and roughly maintained this level until 1457 days indicating strong periodicity in the visitation of the dive site by some adult female tiger sharks as well as inter-annual site fidelity This study provides the first assessment of the population structure reproductive patterns and residency behaviour of tiger sharks at a hotspot in the central Indian Ocean using non-invasive methods While adult females showed inter- and intra-annual site fidelity with temporal residency periods large juveniles showed high residency with shorter periods of absence suggesting that they possibly remain resident in close geographical proximity to the island Fuvahmulah hosts an unprecedentedly large aggregation of tiger sharks year-round which appears to play a critical role for the population’s reproductive cycle i.e This low-effort food source probably attracted tiger sharks to the island long before the tourism activities started and altered their distribution in the area we assume that this large aggregation is a consequence of human activity and that sharks within this study likely present a skewed picture of natural tiger shark population dynamics we recognize that there exists a level of ambiguity regarding the classifications made in this study Our adoption of > 3.0 m TL as a length-at-maturity is a conservative estimate more likely to categorise adult individuals ≤ 3.0 m as juveniles rather than the converse Tunas with massive chunks missing are occasionally observed in the local fishing market likely due to depredation events by tiger sharks (Supplementary Fig these events have not been quantified for the tuna fishery in Fuvahmulah we recommend avoiding generalisations of reproductive cycle lengths within the Indo-Pacific the occurrence of tiger sharks at TH is biased by intraspecific competition We hypothesise that TH is dominated by a subset of the population that shows above-average dominance and aggression Less dominant sharks are likely chased away or avoid close interactions with larger and dominant sharks juvenile females generally avoided the feeding area when adult females were present these behaviours are variable and require further investigation our analyses show the residency to the dive site and not to the waters surrounding Fuvahmulah It is likely that a large proportion of the population was present in the area but avoided the dive site and thus we recommend incorporating all stakeholder’s interests into local management plans that support sustainable ecotourism in one of the world’s largest shark sanctuaries Additional footage of tiger sharks was retrieved during exploratory usage of a remote underwater video station deployed by the Manta Trust and FDS (n = 9 encounters) we calculated the mean to designate sharks in this study accordingly female sharks that were estimated > 3 m were considered as adults and females estimated ≤ 3 m were considered juveniles All tiger sharks were assigned their life stage after size estimates from 2022 If the individuals were not present in 2022 this approach has not been applied to sharks yet Since our data set included photographs of the same sharks throughout their presumed gestation period and subsequent return after parturition we used this method to quantify the observed morphological changes over time To develop a dimensionless and scale-invariant metric for comparisons between photographs we standardised the body widths by a length measure we used the shark’s width from the posterior end of the first dorsal fin vertically down (90° to swimming direction) and the length from the anterior base of the pectoral fin to the anterior base of the pelvic fin to minimise error due to the sharks’ propulsive tail flexing (Supplementary Fig where the picture quality allowed for the quantification of shark widths by having at least ten sufficient pictures spread over at least six months across presumed pregnancies (supplementary Fig We calculated the ratios starting one year prior to a shark leaving for apparent parturition and took three measurements after its subsequent return Sharks that did not fall into the category ‘pregnant’ or ‘not pregnant’ To assess if there was a consistent trend in abdominal distension throughout presumed gestation we applied a linear regression model to the width data until the sharks left The study was conducted following the guidelines and under the research permits issued by the Environmental Protection Agency (annually renewable permit: EPA/2021/PA-F01 and EPA/2022/PA-F02) and the Ministry of Fisheries Maldives (annually renewable permit: 30-D/PRIV/2021/190) The methods employed were non-invasive in nature 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M., D’Alberto, B. M., Smart, J. J. & Simpfendorfer, C. A. Age and growth of tiger shark (Galeocerdo cuvier) from Western Australia. Mar. Freshw. Res.https://doi.org/10.1071/MF20291 (2021) Don’t bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predator: ecological impacts of shark ecotourism & Species catalogue sharks of the world An annotated and illustrated catalogue of shark species known to date Fuvahmulah Atoll ISRA Factsheet (IUCN SSC Shark Specialist Group Ocean acidification and global warming impair shark hunting behaviour and growth Hand feeding can periodically fuel a major portion of bull shark energy requirements at a provisioning site in Fiji Effects of food provisioning on the daily ration and dive site use of great hammerhead sharks Shark depredation in commercial and recreational fisheries localised movements and behavioural segregation of pregnant Carcharias taurus at Wolf Rock An elasmobranch maternity ward: female round stingrays Urobatis halleri use warm restored estuarine habitat during gestation Aggregation behavior and seasonal philopatry in male and female leopard sharks Triakis semifasciata along the open coast of southern California regional trends and inshore environmental conditions influence coral bleaching in Hawaii: CORAL BLEACHING IN HAWAII Concurrent scavenging off a whale carcass by great white sharks Life after death: behaviour of multiple shark species scavenging a whale carcass Social preferences of juvenile lemon sharks Social network analysis reveals potential fission-fusion behavior in a shark Companions and casual acquaintances: the Nature of associations among bull sharks at a shark feeding site in Fiji Social network analysis reveals the subtle impacts of tourist provisioning on the social behavior of a generalist marine apex predator Aquatic animal telemetry: a panoramic window into the underwater world A novel intrauterine satellite transmitter to identify parturition in large sharks and research priorities of shark diving tourism The shark reef marine reserve: a marine tourism project in Fiji involving local communities Grey Nurse Shark (Carcharias taurus) diving tourism: Tourist compliance and shark behaviour at Fish Rock Multi-year effects of wildlife tourism on shark residency and implications for management Measuring whale sharks Rhincodon typus with laser photogrammetry Long-term photo-identification reveals the population dynamics and strong site fidelity of adult whale sharks to the coastal waters of Donsol Eyes on the size: accuracy of visual length estimates of white sharks Paired-laser photogrammetry as a simple and accurate system for measuring the body size of free-ranging manta rays Manta alfredi Risks and advantages of using surface laser photogrammetry on free-ranging marine organisms: a case study on white sharks Carcharodon carcharias First record of a potential neonate tiger shark (Galeocerdo cuvier) at a remote oceanic island in the Eastern Tropical Pacific Underwater ultrasonography and blood sampling provide the first observations of reproductive biology in free-swimming whale sharks Spy in the sky: a method to identify pregnant small cetaceans Assessment of a non-invasive approach to pregnancy diagnosis in gray whales through drone-based photogrammetry and faecal hormone analysis SOCPROG programs: analysing animal social structures Population structure and residency of whale sharks Rhincodon typus at Utila Improving sightings-derived residency estimation for whale shark aggregations: a novel metric applied to a global data set Selection of models of lagged identification rates and lagged association rates using AIC and QAIC R Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria, URL (2022). https://www.R-project.org/ Download references This work was possible through the support of Fuvahmulah Dive School and dedicated staff members (including A Rasheedh) collecting video footage of tiger sharks across the seasons Data collection was also supported by a wide range of citizen scientists and K Zerr (Manta Trust) sharing their footage with us Müller for additional help with study design Open Access funding enabled and organized by Projekt DEAL Leibniz Centre for Tropical Marine Research Marine Research and Conservation Foundation Department of Biological and Environmental Sciences TD and TI designed and conceived the project LV prepared the manuscript and data analysis JC and LV collected data during the period of highest sampling effort from 2021 until 2023 MC designed the original photo identification catalogue and collected data in 2019 and 2020 IS and TI collected data throughout the entire study period AN filmed the predation event on a hawksbill turtle All authors contributed to manuscript revision The authors declare no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Below is the link to the electronic supplementary material Download citation DOI: https://doi.org/10.1038/s41598-024-73079-3 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing: Anthropocene newsletter — what matters in anthropocene research but a population in the island paradise could hold clues to where they breed and give birth with their characteristic stripes and sharp appear from the depths of the Indian Ocean They follow the scent of fish blood and oil coming from tuna heads a research team has hidden under a pile of rocks in a shallow sandy area perhaps eight or nine and up to four metres long two with bite marks on their flanks and fins encounters with more than 20 sharks are not uncommon Tiger sharks circle at the Tiger Zoo dive site Earlier this year, scientists, two local dive schools and the Maldivian shark organisation Miyaru teamed up for a two-week field study to answer the question: why is it that so many tiger sharks gather near the island The findings could help locate what is considered to be the holy grail of shark research: the place where the sharks go to breed and life begins we need to know the habitats that are critical for their reproduction,” says Lennart Vossgaetter a German shark research and expedition company these places are mostly unknown for migratory species such as tiger sharks which roam the oceans over thousands of kilometres he continued what a local dive school had started: documenting which sharks showed up on the dives using photo-IDs A dive guide hides tuna heads under a pile of rocks at the site to attract the sharks we need to know the habitats that are critical for their reproduction,’ he says With the help of three other biologists carrying out identifications “making it the largest known population of tiger sharks in the ocean” He noticed that many got fatter and fatter over time – only to disappear for months and return with flat bellies: did the tiger sharks spend their pregnancy in these waters This would make it a key region for the species’ survival in the Indian Ocean the research team enlisted the help of James Sulikowski He co-leads the Big Fish Lab at Oregon State University and studies shark migration and reproduction It is Sulikowski and his team who planted the tuna heads as bait to enable them to carry out an important but delicate procedure Sulikowski then reaches out with a telescopic pole and presses an ultrasound probe against the shark’s belly James Sulikowski and the team examine sharks for pregnancy with the underwater ultrasound device we need to protect their critical habitats and migration routesLennart VossgaetterBack at the dive club Sulikowksi displays an ultrasound scan of a shark named Aaya: she is indeed pregnant their gills and pectorals are clearly visible “Aaya carries about 40 of them.” When she gives birth after about 16 months – nobody knows for sure how long the gestation is – they will have reached 75cm the researchers scan 35 female tiger sharks Why the females visit this particular region during their pregnancy is unclear “Perhaps because they are safe here from aggressive males,” Sulikowski says “They could also seek out this warm region to accelerate the growth of the embryos as their metabolism depends on the water temperature.” Whatever the reason, it is good news for tiger sharks that one of their reproduction sites in the Indian Ocean, a hotspot of global shark mortality, falls within the protected area of the Maldives Clockwise: a boat at the entrance to the harbour dive site; a beach popular with locals and tourists at the northern end of the island; and fishermen selling tuna In 2017, Tatiana Ivanova and her husband opened the first dive centre on the island, Fuvahmulah Dive School, and sparked a boom in the trade. Now there are about a dozen such centres. The reef-fringed island offers high chances to see big fish such as manta rays, thresher sharks and hammerheads. But its main attraction is the tiger sharks – at Tiger Zoo, sightings are guaranteed. “Ninety-five per cent of our guests come for them,” says Ivanova. Tatiana Ivanova and Ibrahim Siyan, owners of Fuvahmulah Dive School Read moreWhere they mate and give birth the team can still only speculate. “Our guess is that pregnant females visit another atoll in the Maldives,” says Vossgaetter. But they could also swim to the Chagos archipelago, a marine reserve where sharks are caught illegally, or to Sri Lanka, where they are not protected at all. In autumn, the researchers plan to return to Fuvahmulah to follow the progress of the tiger sharks’ pregnancies. In the next phase, they would like to tag females using a newly developed “birth alert tag”, a chicken egg-sized transmitter that is inserted into the uterus. At birth, the tag is released together with the baby sharks and transmits its position via satellite. If successful, it would help better understand the life of tiger sharks and protect this apex predator. Volume 7 - 2020 | https://doi.org/10.3389/fmars.2020.538675 Assessing the resilience of islands toward altered ocean climate pressures and providing robust adaptation measures requires an understanding of the interaction between morphological processes and the underlying hydrodynamic drivers this study presents changing sediment volumes on various temporal scales for the fringing reef island Fuvahmulah aerial imagery provides information on marine aggregates of the island's beaches high resolution climate reanalysis data serves as input into an empirical and a numerical approach both approaches describe the driving processes behind volumetric seasonal and interannual changes: On the one hand the empirical method quantifies sediment transport rates for calcareous sediments over the whole time span of the data set by considering wind and swell waves from multiple directions the numerical method gives insights into the complexity of currents induced by dominant wave components Combining these methods facilitates hindcasting and predicting morphological changes under varying wave climate assessing sediment pathways over the whole reef and describing the seasonal and interannual evolution of the sand spit Thoondu this study reveals sediment distribution on different spatio-temporal scales and elucidates their significance in the design of conventional and alternative low-regret coastal adaptation This shows that sediment erosion and accretion is highly site specific and is sensitive to multiple drivers the evolution of reef islands and their natural response to changing impacts mainly depend on the reef's individual sediment production rate and the sediment distribution under the given hydrodynamic circumstances: monsoon-driven seasonal as well as the annual variations of the local hydro- and morphodynamic regime numerical modeling efforts help to further analyze coral sediment entrainment transport processes and distribution on the reef and around the island dependent on wave directionality and forcing These approaches mimic the natural seasonal and annual variations of the typical local hydro- and morphodynamic regime Considering multi-directional wave input facilitates evaluating characteristic regional and local wave climate as well as following the probable sediment pathway around the island Compared to studies on annual or seasonal scale the hourly temporal resolution of hydrodynamic data gives new and more detailed insights into drivers of morphodynamics on reef islands and thus improves the understanding of sediment distribution scrutinizes the influence of a varying wave climate on reef sediment pathways and thereby showcases reef islands' capability to naturally cope with changing ocean and climate pressures on reef islands this potential must be considered in coastal management and improves conventional and alternative coastal protection measures for sustainable low-regret coastal adaptation Cartopy also delivered the coastlines in (B,C) Figure 2. Wave climate at the ERA5 data node (Figure 1) (A) Shows monthly box plots of hourly significant wave height Hs for a time series from 1979 to 2019 blue boxes are wet season months and yellow boxes are dry season months (B) Shows the discrete marginal distribution between the peak wave direction θp and the significant wave height Hs of the dry season while (C) contains this information for the wet season while (D,E) contain the same information for wind waves the colorbar shows the occurrence probability of each 0.5° wave direction and 0.05 m wave height cell The gray areas visualize the significant peak direction range θp containing the directions which combined have the highest 33 % occurrence probability Table 1. Wave parameters for the time series at the ERA5 data node (Figure 1) Three field campaigns provided data to evaluate the seasonal and annual sedimentation processes around the island: The first campaign started in March 2017 at the end of the dry season The second field campaign took place at the end of the wet season in September 2017 revealing seasonal variations in combination with the former measurements in March The last field measures were taken in March and April 2019 disclosing seasonal and annual changes of sediment volumes when compared to the data recorded in 2017 The first field campaign also accommodated a bathymetric survey recording depth profiles with a dual-frequency echo-sounder (Dr the field campaigns yielded the following data sets: Quantum GIS (version 3.4.11.) uses the rastered topography provided by Photoscan to calculate the seasonal or annual changes of the coastal topography with resulting in a difference of topographic height Δzi, j for each pixel of the rastered DEM. All further post-processing (Figure 3) was performed with the Python module Rasterio (version 1.1.1): The total volume change in each of the ΔDEM is calculated with ΔVmc equals to ΔVDEM but only within the boundaries of the morphological cell (index mc) Summarizing the areal sediment volumes of each morphological cell for the entire island with the absolute areal sediment difference quantifies the morphodynamic activity and gives an estimate on the average shoreline change (index sc): Average areal sediment budgets from DEMs with (A) seasonal sediment budget from dry to wet season based on the data of March 2017 and September 2017 and (B) annual sediment budget between dry season 2017 and 2019 (both recorded in March) sediment accumulation for the observation period is blue The volumetric change of sediment [m3] is averaged over dry beach area [m2] (see Equation 4) dashed) come from measurements in the first field campaign (March 2017) Location of sediment volumes and profiles (orange lines) for the dry season 2017 (red colorbar) and wet season 2017 (blue colorbar) in the north of Fuvahmulah In the dry season sand depots form at the adjacent beaches Geiymiskih Fannu in the west (profile 1) and Thoondu in the east (profile 3) of the headland The wet season allocates sand on the north tip of the island The dry season sand volume of eastern Thoondu beach (profile 3) was integrated over differences of six accuracy-improved profiles The profile elevation N is given as distance to the WGS84 ellipsoid The background satellite image contains Copernicus Sentinel data (true color large areas of the reef were covered with sand in the dry season making vGCP assignment on the sea-side of the beach impossible so that DEMs contain areas with either poor or without referencing six beach profiles support the estimation of sand volumes on the dry season Thoondu beach The profiles have been manually referenced to the plain beach in wet season provided by ©OpenStreetMap contributors Combining the annual areal carbonate production rate with the reef platform gives the total annual estimate of sediment volume produced on the reef as with a measured sediment density of ρs= 2 g cm−3 The CERC-formulation or Shore Protection Manual (SPM)-method for longshore sediment transport (CERC, 1984) uses the longshore component of wave power as longshore wave energy flux Converting Equation (7) to deep water parameters with n0 = ½ yields: here with salt water density ρw of 1.03 g cm−3 sediment density ρs of 2 g cm−3 The empirical coefficient K is the transmission between wave-induced energy flux and sediment parameters. It accounts for the heterogeneity of beach sediments and the local coastal environments. The coefficient translates the wave energy impact on site into the site-specific sediment motion by calibration with measured data (Schoonees and Theron, 1995) K facilitates matching the measured with the calculated total sediment volume of the field campaigns in 2019 the total sediment volume transported on a coast for all wave partitions is with wpww for wind waves and wpSi for swell waves with i for each of the three swell partitions of the ERA5 data set With the sediment volumes measured in the 2019 dry season field campaign for the northwest (NW: 14.689 m3) and east coast (E: 1.171 m3) the empirical coefficient K becomes KNW = 55.89 and KE = 107.26 When illustrating results from the CERC method based on the hourly ERA5 data between January 2016 and November 2019 this study smooths the data with a combined windowed forward and backward average filter based on with a window of n = 24 h·7 d. Filtering was applied on Hs (depicted in Equation 12), θp, qy, and Qy (analogous to Equation 12). Smoothing accounts for a delayed response of the morphology to wave energy forcing (Rutten et al., 2017) Fuvahmulah has two seasons: the wet or rainy season from May to October and the dry season from November to April. Between the wet and the dry season, waves differ in height as shown by the ERA5 data set (C3S, 2017) of the ECMWF (Figure 2). While the dry season brings northeastern winds, Fuvahmulah is subject to mainly south to southwestern Monsoons in the wet season (MEE, 2014) The Monsoons are accompanied by high waves with the highest median significant wave height in July (H~s,max.=1.72m) while the highest total significant wave height was registered on November While this study defines November already as dry season the wave data discloses a transition phase between wet and dry season The lowest annual median value H~s,min.=1.12m appears in March (dry season) These parameters are used to describe the dominant features of wave heights Around Fuvahmulah, total swell has a higher seasonal variation of Hs but less spreading or directional variety of associated peak wave directions θp than wind waves (Figure 2 and Table 1) Swell waves are rarely below 1 m in the wet season (Figure 2 ts are coming from south to southwest in both seasons however the dry season contains additional directional components between ~45 and 135° Wind waves have a mean significant height of H¯s,ww=0.26±0.28m (in both seasons, Figure 2 and Table 1) The highest wind waves approach the island from west The two significant differences among seasonal wind waves are (a) in the dry season waves reach Fuvahmulah dominantly between 238 and 75° while they approach the island with 122–287° in the wet season and (b) an additional north to west (0–90°) component in the dry season being absent in the wet season Both differences have a considerable influence on the sediment transport in the northern part of the island and the sand spit Thoondu The Gnaviyani Atoll reef is mostly sub-tidal with an inter-tidal reef-flat around Fuvahmulah The sub-tidal reef fringes the inter-tidal plateau before it expands to an about ~2.2 km long and 1.6–0.5 km wide fore reef in the south east This southern fore reef makes about 58.8 % of the total reef area the depth is ~ 25 m and slowly decreases to around 8–15 m until reaching the inter-tidal reef The reef form is elliptical with the long axis approximate to the dominant swell wave direction θp ~ 157.5° The transition from sub-tidal fore reef to intertidal reef on the south and west side is sudden while it is more gradual on the north and east side of Fuvahmulah The inter-tidal reef is wider on the south and west side (around 85–145 m) than on the north and east side (around 15–25 m) The island oscillation index Io describes the morphodynamic activity of an entire island by comparing the island's perimeter with the coastal area encompassing more than half of the maximum (seasonal) coastline change The coastline change is linked to the beaches' volumetric changes and—in this study—estimated by integrating seasonal and interannual sediment differences over 12.5 m wide areal increments of Fuvahmulah's coast The underlying sediment differences required for this procedure originate from the DEMs of the UAV surveys Using this information for the island oscillation index leads to a low Io of Io = 350° − 315°/360° = 9.7 %. Such low oscillation indices on elliptical islands indicate that the elongated, lateral shorelines are meant to be morphologically stable (Kench and Brander, 2006) if not obstructed by artificial interference (Kench, 2012) Focusing on the prominent morphodynamic area in the north of Fuvahmulah discloses the seasonal formation of the Thoondu spit: The UAV-borne data of the two field campaigns in 2017 discloses a positive seasonal sediment balance The instantaneous records do not contain the maximum depot sizes as the seasonal difference in sediment volume is +12.307 m3 In the field campaign during the dry season of 2019 sediment depots formed at the same locations as in the dry season 2017 the depot in the west (Geiymiskih Fannu) was considerably larger when compared to 2017 (14.689 m3) while the eastern depot was smaller (1.171 m3 the sediment volume recorded in the dry season of 2019 is 15.860 m3 This is an additional sediment volume of +6.361 m3 over the dry season of 2017 while it is -5.946 m3 less than in the wet season of 2017 the empirical and numerical methods can capture the spatio-temporal sediment transport over the reef (B) Current velocities from the depth-averaged phase resolving numerical wave model (BOSZ) for waves approaching the island from θp = 135° (C) θp = 157.5° and (D) θp = 202° The background color shows the magnitude of wave induced current velocity on the reef while the arrows depict the local current direction Dashed red contour lines are the reef depths −5 and -15 m recorded in the first field campaign (March 2017) Table 2. Beach orientation as well as longshore sediment transport directions and energy flux rates Py, i from the CERC-formulation (Figures 5A, 7, 8) max and the contribution of each wave partition to Qy) The time series shows values from January 2016 to November 2019 while negative values lead to sediment transport toward Thoondu beach in the northeast The time series shows the dry season with orange and the wet season with blue background Field campaign 1 and 3 (orange hatched area) took place in March 2017 and 2019 Field campaign 2 (blue hatched area) was conducted in September 2017 Table 3. Peak transport rates qy, max and the contribution of each wave partition to the total transported sediment volume Qy in the CERC-formulation between 2016 and 2019 on the northern beaches Geiymiskih and Thoondu (NW: Figure 7 and E: Figure 8) The resulting dominant longshore sediment transport direction is toward Thoondu beach (67.9 %) The dominant sediment transport toward Thoondu is commonly found in the course of the wet season usually peaking between July and early September Southward components only appear in dry season wp indicate a transport toward the seaport in the southeast while positive values lead to sediment transport toward Thoondu beach in the northwest After the Thoondu spit formed in the wet season the dry season wave climate leads to sediment depletion of the Thoondu spit while new sediment accumulations form on Geiymiskih and Thoondu beach Figure 9. Sentinel satellite images of northern Fuvahmulah on October 9, 2016 (A) and November 28, 2016 (B) and longshore sediment transport on Thoondu (C) and Geiymiskih Fannu beach (D) at the associated time of the satellite images (green line). (C,D) Show zoomed data from the longshore sediment transport rates qy, wp (Figures 7, 8) The orange hatched area shows the time of the first field campaign for this study The satellite images contain Copernicus Sentinel data Sediment distribution on a reef is subject to (a) hydrodynamic forcing defining wave propagation and thus current direction on the reef platform as well as (c) sediment supply of the reef This study used wave data from the climate reanalysis model ERA5 in the process-based empirical CERC method and the phase-resolving depth-integrated numerical model BOSZ to study the associated morphodynamic response on the Maldivian reef island Fuvahmulah the study linked these insights to comprehend measured shoreline changes on the island's beaches and the seasonal formation of the sand spit Thoondu in the north of the island These factors—the good spatio-temporal data availability and trustworthy reconstruction of the wave climate—facilitate event based hind- and forecasting in the CERC formulation the sheer amount of wave data results in a challenging number of feasible and reasonable numerical simulations this study combines the empirical CERC-formulation with information of a numerical model calculating wave-induced currents approaching Fuvahmulah from the dominant wave directions: The sediment transport rate qy itself focuses on longshore sediment distribution but gives no information on cross-shore beach response (Atkinson et al., 2018) or cross-shore transport components the CERC-approach cannot estimate sediment transport toward the island and thus the role of the southern Fuvahmulah reef as sediment source The numerical models also disclose an influence of south to southeastern swells on the lee-side of the island but these are outside the northern beaches' incident wave direction range θ⊥ of −90–90° and thus remain unconsidered in the CERC-equation The insights from the numerical model complement the findings of the CERC-method and put the measured morphological changes into an hydrodynamic context erosion must be studied on a different scale Ocean climate pressures influence sediment production and distribution pathways on the reef The dynamic reef island morphology is a natural response to changing impacts low-regret coastal development requires an understanding of the underlying processes of island morphology Morphological changes on the reef are triggered by hydrodynamic forcing. Therefore, this study exploits hourly climate reanalysis model wave data to quantify longshore sediment distribution around the island with the CERC method. Dominant south to southeasterly swells are characteristic for the regional Maldivian hydrodynamic regime (Kench and Brander, 2006; Kench and Mann, 2017) These swells induce a constant sediment supply from the southeastern reef plateau The sediment stream goes around the lateral sides of Fuvahmulah to the northern headland where the Thoondu spit forms in the wet season Local wind-wave and subordinate swell events shape the northern beaches within the seasons By adapting and validating the empirical coefficient K with the measurements from the field campaigns the CERC formulation is capable of capturing morphodynamic changes after hydrodynamic events This method facilitates processing the high resolution wave data from the climate data models for quantitative hind- and forecast of longshore sediment transport Numerical methods give supplementary insights beyond the empirical CERC approach and hence a more holistic view on the complex hydrodynamic background of the reef for certain combinations of dominant wave parameters or single events further advances in numerical models are required to directly couple hydrodynamic drivers and morphodynamic response on reef islands and calcareous sediment sediment trajectories reveal locations with increased erosion potential on the lee-side of disturbances in the natural sediment stream Because anthropogenic interventions into the natural dynamics disturb the natural ability to respond to ocean climate pressures the design of coastal infrastructure on low-lying reef islands must include an assessment of reef islands' natural beach nourishment potential to avoid interference before taking action reef island communities can reduce shoreline erosion improve their resilience and decrease their risk to suffer from sea level rise and associated impacts The field data supporting the findings of this study are available from the corresponding author upon reasonable request. Wave climate data is available from the Copernicus Climate Change Service (C3S, 2017) Satellite images from Copernicus Sentinel data were accessed through the EO Browser and wrote the manuscript with input from TS All authors contributed to the article and approved the submitted version This study took place in the project Dealing with change in SIDS: societal action and political reaction in sea level change adaptation in Small Island Developing States (DICES), grant no. SCHL 503/17-1. The project was framed within the priority program (SPP 1889) ‘Regional Sea Level Change and Society’ (SeaLevel, see www.spp-sealevel.de) of the German Research Foundation (Deutsche Forschungsgemeinschaft The publication of this article was funded by the Open Access fund of Leibniz Universität Hannover The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest and Uwe Zander for their help in the field campaigns the authors were supported by the Maldives Meteorological Service (MMS) The authors further appreciate the involvement of the working group of Maike Paul for reviewing the manuscript We further acknowledge the working group of Jan Visscher as well as our project members in DICES Susann Adloff and Katrin Rehdanz for their professional input Additionally the authors thank Volker Roeber and Jannek Gundlach for their feedback concerning numerical models as well as Jean Bidlot and Todd Spindler for their help in accessing climate reanalysis data Elisa Casella and Alessio Rovere gave valuable insights and feedback to UAV-based photogrammetry while Tobias Kersten helped with geodetic questions before the third field campaign and while post-processing The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2020.538675/full#supplementary-material A fundamental paradigm for coral reef carbonate sediment dissolution CrossRef Full Text | Google Scholar Laboratory investigation of the bruun rule and beach response to sea level rise Swash–groundwater interaction on a steep gravel beach CrossRef Full Text | Google Scholar Reading: European Centre for Medium-RangeWeather Forecasts (ECMWF) Google Scholar Google Scholar “Design tools related to engineering,” in Environmental Design Guidelines for Low Crested Coastal Structures C3S (2017). 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This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) distribution or reproduction in other forums is permitted provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited in accordance with accepted academic practice distribution or reproduction is permitted which does not comply with these terms *Correspondence: C. Gabriel David, ZGF2aWRAbHVmaS51bmktaGFubm92ZXIuZGU= Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher. 94% of researchers rate our articles as excellent or goodLearn more about the work of our research integrity team to safeguard the quality of each article we publish. beyond the country’s legendary resorts cruising between atolls on a luxury liveaboard tasting regional food grown on local farms observing goldsmiths crafting traditional necklaces These may not be typical activities associated with the Maldives a tropical archipelago best known for its high-end resorts holiday experiences can find Maldivian guest houses or liveaboards that open doors to new perspectives and unlock access to new experiences Perhaps one of the most thrilling of these is the bucket list-worthy experience of diving with huge aggregations of tiger sharks “We have arguably one of the biggest tiger shark aggregations in the world,” says Fuvahmulah-based shark guide Hamna ‘Hamty’ Hussain are always located on inhabited islands (unlike resorts which are each on a private island of their own) This offers you the unique opportunity to live alongside Maldivians and interact with the community as well as support locally owned services such as dive centres Liveaboard sailing adventures can also open opportunities to experience island life chat with Maldivians and maybe even hear some mesmerising tales There are shipwrecks all over the Maldives – one of the oldest dates back to the 1700s – and some of them According to Maldivian oral history shared across generations the Sultan of the Maldives’ goldsmith was banished from Malé to Rinbudhoo after being accused of stealing Islanders say he was one of the best goldsmiths in the Maldives and passed down his skills to the people of Rinbudhoo Islanders dove to retrieve gold from shipwrecks to use in their workshops and became the best goldsmiths in the Maldives it was said that every house in Rinbudhoo had a goldsmith you can still observe goldsmiths in action As you wander around the streets of this peaceful island stop by a tea shop to try some delicious hedika (Maldivian afternoon tea) with locals made from Rinbudhoo’s unique curry blend of havaadhu spices Due to the island’s tiny population (about 429) the island has an atmosphere of tranquillity with most of the inhabitants staying indoors under fans to avoid the heat of the day only to emerge and socialise in the early morning and evenings Running the length of the sleepy island are vibrant murals depicting Maldivian life They are framed by an arch shaped like a golden fahtaru (gold necklace) representing Rinbudhoo’s legendary goldsmiths You can create your own island-hopping itinerary of local experiences in a cost-efficient way by utilising MTCC public ferry (dhoni) routes Many guest houses or water-sports centres go beyond the typical offerings such as jet-skis and snorkelling They bring you more uniquely Maldivian experiences such as sandbank picnics traditional pole-and-line fishing trips at sunset and local cooking classes save time by taking a domestic flight or consider a scheduled speedboat as an exhilarating alternative Using high-speed scheduled routes such as the RTL ferry a 500-year-old wooden palace in Utheemu island in the north of the country Utheemu Ganduvaru was once the home of Sultan Mohamed Thakurufaanu who overthrew the Portuguese in 1573 It was a time when fishing villages and agricultural smallholdings were the norm Just a couple of hops by local ferry from Rinbudhoo to South Ari Atoll is Dhigurah a long shard of emerald green surrounded by azure waters a guesthouse more akin to a stylish boutique hotel join a liveaboard with a Central Atolls itinerary passing near (or docking at) Dhigurah plus shared daily experiences such as diving and island visits a sense of camaraderie typically develops fast among passengers with the chance of making lifelong friendships past the candy-coloured bungalows adorned with tropical flowers Chat with a local relaxing on a joali (hammock chair) in the shade watch boat-builders working on the beach and observe fishermen bringing their catches into the harbour The fishing village is limited to just one end of this 3.2km-long leaving more than 2.4km of untouched white sand Another way to explore the Maldives is through its cuisine Thoddoo in North Ari Atoll is a patchwork of green fields and orchards located just 80 minutes by speedboat from Malé and among fields bursting with juicy cucumbers and scotch bonnet chillies Travellers can self-guide or book a farm tour through their guest house to learn about Thoddoo’s 112 farms Maldivian chef Nasreena Ali is feted for promoting homegrown Maldivian cuisine having shared her expertise at dining venues in Auckland and around the Maldives She is currently a sous chef at Dhigali Maldives “We use a lot of spices in traditional food “The taste of Maldivian cuisine is different Maldivian chillies and coconut milk.” A visit to Thoddoo wouldn’t be complete without sampling its bounty at a farm-to-table eatery Try the popular mas’huni and roshi (Maldivian breakfast of fresh tuna with onions accompanied by a farm egg and hot sweet tea) Or tuck into a lunch of grilled Maldivian octopus with a fresh salad of cucumber and peppers the cuisine typically has strong ties to the ocean but some islands like Thoddoo are very important islands for agriculture,” says Nasreena “Thoddoo is particularly famous for its watermelons or ‘Thoddoo karaa’ in Maldivian language.” The jewel in the crown of the Maldives’ aquatic world is Baa Atoll Unesco World Biosphere Reserve It’s home to globally significant biodiversity the manta and whale shark “feeding frenzy” at Hanifaru Bay is the star attraction This phenomenon sees extraordinary aggregations of manta rays attracted by zooplankton that get trapped in the horseshoe-shaped bay Fayyaz Ibrahim comes from a family of divers his father was the first Maldivian scuba diver and his uncle was the country’s first certified diving instructor Fayyaz has worked on liveaboards and as an instructor for 42 years: “The mantas go into a feeding frenzy when they see the plankton and sometimes on a good day you can see 200 there,” he says only a licensed guide can take you for snorkelling and there are special rules and rangers looking after the base While Baa Atoll is an excellent location for snorkelling or learning to dive the Maldives also offers thrilling experiences for more advanced divers Fuvahmulah in the far south offers one of the Maldives’ most unforgettable experiences – diving with tiger sharks Fuvahmulah’s only female shark guide Hamna Hussain says: “Fuvahmulah is below the equator and it’s a one-island atoll There are no other islands nearby and there’s no lagoon It’s basically a pinnacle that just comes out of the deep water we get all sorts of pelagic creatures like tiger sharks we have some of the biggest aggregations of oceanic mantas and one of the best coral reefs I’ve ever seen in the Maldives.” Tiger shark season runs from February to April in Fuvahmulah These are just a handful of the diverse experiences to be discovered in the Maldives liveaboards and islanders willing to share Maldivian culture with visitors and year-round opportunities for adventure people were coming during the European winter season,” says Fayyaz “But now even in the European summer season people come for the liveaboards and for my country.” sand and sea of the sunny side of lifeBreathtaking views Sitting just under the Equator at the southern extreme of the Maldives is the little-visited island of Fuvahmulah It is very different from the hundred or so holiday resort islands dotted throughout the 800-kilometre chain of coral atolls stretching northwards in the Indian Ocean that make up the archipelago This 4.5-kilometre by 1.2-kilometre island is a living working community of more than 8,500 people infinity pools and water villas of the luxury resort-only islands it is the third most populous island in the Maldives It is also one of the few Maldivian islands that is not surrounded by a coral lagoon it is a volcanic bowl with the interior covered in tropical woodlands This unique habitat within the Maldives is rich with endemic plant and animal species It is a vital staging post for migratory birds – more than 167 bird species are found on the island Maldivians consider Fuvahmulah the most beautiful of the 1,200 islands that make up the archipelago It is a one-island atoll and the third-largest in size in the Maldives (excluding those such as the new Dhaalu international airport island which was extended by land reclaim) Unlike most other islands it has working farms growing mangoes pineapples and a range of vegetables such as aubergines and peppers which separates Huvadhu Atoll from Addu Atoll Fuvahmulah has long been a centre of tuna fishing There is evidence that for more than 1,000 years The rich waters surrounding the island are brimming with not just tuna but other pelagic species such as scalloped hammerhead sharks melon-headed whales and a substantial population of tiger sharks which extends for about three kilometres to the island’s southeast These natural wonders led to UNESCO declaring Fuvamulah a biosphere reserve in 2020 – the only such reserve in the Maldives Fishing is still the main occupation on the island The locals use pole-and-line techniques which keep fish populations healthy and sustainable for future generations which have decimated many other tuna fisheries The islanders live by the philosophy of taking from the ocean and giving back to the ocean This means that once they’ve gutted the fish Herein lies the reason why this island is so special and could soon be joining the ranks of Cocos Island and the Galápagos Islands as one of the very best shark-diving destinations on the planet a vast population of tiger sharks have become habituated to feeding on these scraps A recent count identified more than 160 individuals hanging around a ledge outside the harbour entrance It is thought that hundreds more are regular visitors to the waters around the island making it quite possibly the home of the largest concentration of tiger sharks on the planet Add to that the bounty of the other pelagics found in the area plus the remarkable reef-fish biodiversity and you have a very special diving destination His friends call him Lonu (the local word for saltwater) as Nasheed Ahmed was always in the ocean surfing (one of the advantages of not being surrounded by a coral lagoon is that the waves break onto the beach) he decided he wanted to see the ever-present tiger sharks on their own terms and jumped into the water at the edge of the harbour Milling around the sandy rubble outside of the harbour were dozens of tiger sharks He soon noticed that a significant number were heavily pregnant females They seemed mildly interested in him but far more engaged with feeding on the tuna scraps he opened the first dive centre on the island He also founded the Fuvahmulah Marine Foundation to help conserve the island’s biodiversity and organise and regulate the shark diving Very few tourists and even fewer divers were visiting the island back then like a saltwater version of the Kevin Costner movie Field of Dreams first among dive guides working on the resort islands and intrepid independent travellers started to arrive but more and more divers are now coming to share Lonu’s passion I visited Fuvahmulah with my wife Louise and four other divers with Ocean Culture Life in February this year Our trip was guided by underwater photographer Jono Allen The first time you jump into the water outside the harbour you are glad you are with Lonu and have absorbed his thorough briefing As you settle on the sand between eight to ten metres depth (depending on the tide) it takes some getting used to when you realise you are surrounded by maybe five or even ten tiger sharks The most tiger sharks we encountered at one time was 16 Evolution hasn’t equipped humans with 360-degree vision leaving you feeling quite vulnerable at times I began to take in the scene unfolding in front of me There was a distinct hierarchy among the sharks they left the ledge and slipped gently into the darkness; the younger sharks would come in to fight over the scraps These younger sharks darted around more quickly than the larger meaning you had to be more vigilant when they were nearby you realised the sharks had distinct personalities Some were hyper-inquisitive and would turn abruptly towards you to see if you were hiding fish from them They seemed like puppies looking for scraps from the dinner table Other would sedately glide past with a wary eye on you as if to say ‘Stay there this is my kingdom and I’m tolerating you’ They behaved much like a strange dog might do if it came across you on a beach – bouncing up At no point did I or my fellow divers believe we were on the menu But this seemed to be friendly curiosity; as Jono put it While the shark dives were the trip’s high point The reefs were some of the healthiest I have seen in the Maldives in decades skirting around triggerfish guarding their eggs Fuvahmulah is going to change over the next few years I can only hope that the efforts of Lonu and people such as Jono safeguard the island’s future and that the divers who come to see the tiger sharks and all the other marine delights treat this extraordinary island with the respect it deserves TAXONOMY: The tiger shark is a type of requiem shark of the Carcharhinidae family and the only living member of the genus Galeocerdo Like all of the 270 different species of Carcharhiniformes five-gill slits and has nictitating membrane over its eyes SIZE & WEIGHT: Adults commonly reach between 3.25m and 4.25m in length and weigh up to 635 kilograms There are records of exceptionally large females reaching in excess of 5m in length One pregnant female caught in Australia measured 5.5m and weighed 1,524kg It is the fourth-largest extant shark and the second-largest predatory shark (the great white being the largest).DISTRIBUTION & HABITAT: Found around the world in tropical and temperate waters it stays on or near the continental shelves and ranges from the surface to depths of 900m It is often found in estuaries and near harbours Another common haunt is around coral atolls it is found from Japan down to New Zealand it is found throughout the East African coast in the Maldives and around the shores of India and Southeast Asia Tiger sharks can be seen in the Gulf of Mexico and in most of the Caribbean and there are even recorded sightings in the Mediterranean DIET: Larger tiger sharks tend to swim close inshore at night to feed and head out to deeper waters during the day such as around Fuvahmulah harbour in the Maldives will attract large specimens during the day They will eat sharks and rays and even other tiger sharks A study in Australia found the remains of dugongs in 15 of 85 tiger shark stomachs examined Another study in Hawaii found remains of terrestrial mammals REPRODUCTION: Tiger sharks bear very large litters with an average of between 26 to 33 pups born in spring to early summer Mating occurs in spring – sometimes before pregnant females have given birth They are the only species in its family that is ovoviviparous – that is Sexual maturity is when the males reach 2.8m to 2.9m in length GROWTH: Tiger sharks are fast-growing and reach maturity between four and 13 years It is thought they live to at least 22 years with some studies suggesting they may live as long as 37 years RANGE: They are strong swimmers and have been known to undertake lengthy solo migrations possibly for reasons of mating and pupping Some tiger sharks have been tagged and discovered to journey thousands of kilometres a year There are also semi-resident populations which barely move 100 kilometres each year Most tiger sharks appear to be fairly solitary when mature but there are aggregations when adults gather to feast on seasonal food supplies such as the fledging of albatross chicks in the Pacific THREAT: IUCN Red List – Near Threatened:  In the Indian Ocean tiger sharks have been intensely targeted by fishing Its large fins are also prized in the Hong Kong markets but there is some evidence that juvenile survival rates increase when adults are depleted.DIVING WITH TIGER SHARKS: Usually tiger sharks are unaggressive when encountered underwater by divers and are commonly seen in shark-feed dives in The Bahamas and now Fuvahmulah The island was only opened to tourists in 2016 it has had relatively rapid growth in tourism infrastructure with small guesthouses and B&Bs opening up a handful of dive centres and a smattering of restaurants and cafés catering for travellers it is important to realise that this is not the luxury end of the travel market that anyone who has been to the Maldives in recent years will have experienced A round-trip fare is approximately US$480 per person The adventurous could take a cargo boat from Malé to Fuvahmulah You can also reach Fuvahmulah by ferry from Addu Atoll in the south Ferries are operated by Southern Transport Link and take between 45 and 90 minutes Tickets need to be pre-booked and cost around US$20 each way Addu Atoll is served by Gan International Airport in Addu City plenty of Indian and Asian cuisine and even a touch of Mexico New cafés and restaurants are opening up every month so ask around about the latest places.Pebbles: Tables under thatched gazebos close to Thoondu Beach serving traditional Maldivian delicacies along with Thai Indian and other international cuisines.Royal Restaurant: Near the harbour with a wide range of curries and seafood available One of the best places to try Kattelhi fish stew – a local delicacy made from a rare deepwater fish that in the Maldives is only found on this island Pre-order for the best fish.Real Breeze: Great Indian curries and the fish buns have a dedicated following.Runway 29: Small Good ‘Hedhikaa’ menu of snacks and small meals GETTING ABOUTAn asphalt road runs from the airport much of the streets are unpaved and uneven Most of the island is accessible via bicycles available for hire at shops and some hotels and guesthouses Motorbikes are also a popular method of transport and readily available for hire There is also a very efficient taxi network with pre-booking only.  DON’T MISSThoondu Beach: Located towards the north of the island It also has the only surf break in the Maldives Surfing has recently become popular with the islanders and while there are as yet no schools most hotels can arrange surf sessions with skilled locals The Lakes: Bandaara Kilhi and Dhadimagi Kilhi form the island’s Nature Park surrounded by stunning vegetation and endemic wildlife MONEYThere are a few ATMs and a couple of banks which do foreign exchange US dollars are widely accepted but in grocery stores Some hotels and restaurants take credit cards Want to access DIVE on your tablet or smartphone Android or PC/Mac image below to download the app for your device Copyright © 2025 Syon Media The Indian Ocean archipelago has the third largest population in the world 1,000 individual oceanic manta rays have now been identified in Maldivian waters. According to the Maldives Manta Conservation Programme (MMCP) – the Manta Trust’s flagship project which confirmed the 1,000th individual – this makes the Maldives home to the world’s third largest population of the species The manta has been named ‘Anbu’ which means mango in Dhivehi Oceanic mantas (Mobula birostris) are the world’s largest species of ray Their wingspan can reach up to 7 metres – almost as long as an iconic London Routemaster bus – hence why they’re also known as giant mantas can be identified by the markings on their underside “Manta rays can be identified by the unique spot pattern on their belly, much like a human fingerprint,” explains Fauz Fath-hee, RahVeshi Programme Coordinator at MMCP to take a photo of the spots on the manta rays’ bellies and we log each sighting in our ever-growing database.” The charity has been studying mantas in the Maldives since 2005 but has ID photos going as far back as 1996 Citizen scientists and local scuba diving centres have also contributed photos in support of this important research Although the Maldives is made up of 1,200 islands nearly all sightings (85%) were from Fuvahmulah Atoll a pelagic island in the south of the country known for its tiger shark dives.  With 1,000 individuals in its waters, the Maldives is home to the world’s third largest population of giant mantas (it also has the most reef mantas (Mobula alfredi) in the world, with over 5,000 individuals) Ecuador has the largest oceanic manta population, “with 2,803 confirmed individuals but an estimated 22,316 individuals based on Proyecto Mantas Ecuador’s data,” says Fath-hee The Pacific Manta Research Group has identified nearly 1,400 individuals in the Revillagigedo Archipelago in Mexico’s Eastern Pacific waters “so the Maldives population is very close to becoming the second largest,” he adds with the Indonesian archipelago of Raja Ampat in fourth with 588 individuals.  The researchers don’t yet fully understand why there are so many manta rays in the Maldives “Unlike other oceanic manta ray aggregation sites cleaning or courtship behaviour observed,” says Fath-hee who believes the rays may be transiting through because they are usually seen for only a day or two and re-sighting rates are low.  “Where they are coming from and where they are going is still a mystery.” he says.  According to the IUCN Red List of Threatened Species, oceanic mantas are endangered so confirming there are at least 1,000 individuals gives conservationists hope they are concerned the animals might be swimming on to Sri Lanka “Oceanic manta rays are known to swim great distances with some individuals traveling thousands of kilometres in search of food has the world’s largest oceanic manta ray fishery and is believed to catch around 1,000 individuals each year “There’s a high possibility that these rays could be moving between the protected waters of the Maldives and Sri Lanka’s waters where they face a high risk of being fished,” he says.  You don't have permissions to access this page