Search

The East African country of Djibouti is known to host an important seasonal feeding aggregation of whale sharks that allows the frequent observation of their surface feeding behaviour. The influence of environmental factors on the different whale shark feeding strategies (passive, active, and vertical) was studied over a four-year period (2017, 2020, 2022, 2024) in the Gulf of Tadjoura. Across 81 immature male whale sharks identified and 1082 surface feeding behaviours recorded in this period, the chlorophyll-a concentration was the main parameter predicting the choice of the filter-feeding technique. Active and vertical feeding behaviours were associated with rainfall, lower sea surface temperature, worse sea conditions, and low wind speed during the morning, all factors positively correlated to chlorophyll-a concentration. On the contrary, passive feeding behaviour was favoured in the inverse environmental conditions. Both passive and vertical feeding behaviours occurred during El Niño events, whereas active feeding was more common during La Niña events. Since it is known that whale shark abundance and distribution are associated with food availability at coastal locations, it is fundamental to understand environmental drivers of filter-feeding strategies when managing conservation efforts for this endangered species. Recommendations for future research work at this site are presented. [ABSTRACT FROM AUTHOR]

Rhincodon typus, or the whale shark, is the largest extant fish in the world and is classified as endangered on the IUCN's Red List. Due to their enormous size and conservation status, whale sharks are rarely housed in aquaria. Here we present a behavioral analysis culminating from a large effort by 89 observers from 2008-2012 to study four R. typus (ID codes: AL, TA, TR, YU) longitudinally in an aquarium setting. We found that relatively simple behavioral metrics such as swim speed, depth occupation, swimming direction, and lead-follow interactions demonstrated R. typus individual variation and responses to habitat changes. All sharks displayed increased swim speeds 30-minutes before regimented feed times, when there was scent of food being fed to other animals in the habitat. Consistently in the habitat, one male shark (YU) was recorded swimming more at depth, faster, almost exclusively clockwise, and engaged in fewer close proximity interactions with others than expected by chance. In contrast, a larger female shark (AL) was observed swimming the slowest, at the surface more than others, led other sharks more than she followed, and had strong lead-follow interactions with another shark of the opposite sex (TA). TA and TR did not differ from each other in depth profiles or speed, but did differ in their proclivity to lead or follow. Depth preferences and lead-follow interactions suggest some partitioning of the habitat and the possibility of social hierarchy in this species. These results represent the first longitudinal behavioral analysis of aquarium R. typus, offering meaningful similarities and contrasts to field observations. [ABSTRACT FROM AUTHOR]

Context: Satellite telemetry has revolutionised the study of animal movement, particularly for mobile marine animals, whose movements and habitat make consistent, long-term observation difficult. Aims: Summarise the movements of Rio Lady, a mature female whale shark (Rhincodon typus), to characterise these movements, and to predict expected behaviour throughout the Gulf of Mexico (GOM). Methods: Rio Lady was tracked using satellite telemetry for over 1600 days, generating over 1400 locations and travelling over 40,000 km. State–space and move persistence modelling enabled characterisation of behaviour, and machine learning (ML) enabled the development of habitat-suitability models to predict habitat utilisation, on the basis of location transmissions and their environmental covariates. Key results: Rio Lady exhibited annually consistent patterns of movements among three regions within the GOM. Final ML models produced seasonally dynamic predictions of habitat use throughout the GOM. Conclusions: The application of these methods to long-term location data exemplifies how long-term movement patterns and core areas can be discovered and predicted for marine animals. Implications: Despite our limited dataset, our integrative approach advances methods to summarise and predict behaviour of mobile species and improve understanding of their ecology. Satellite telemetry enables the study of marine species where observation is difficult owing to their movement across oceans. Rio Lady, a mature female whale shark, has been tracked for longer than any other whale shark and has generated movement data for more than four consecutive years, providing insight into the interannual movement patterns for this species. The combination of these data with machine-learning and habitat-modelling techniques provides a new framework, with potential for enabling new methods of conservation. [ABSTRACT FROM AUTHOR]

Copyright of Jurnal Ilmu dan Teknologi Kelautan Tropis is the property of IPB University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rhincodon typus, or the whale shark, is the largest extant fish in the world and is classified as endangered on the IUCN’s Red List. Due to their enormous size and conservation status, whale sharks are rarely housed in aquaria. Here we present a behavioral analysis culminating from a large effort by 89 observers from 2008–2012 to study four R. typus (ID codes: AL, TA, TR, YU) longitudinally in an aquarium setting. We found that relatively simple behavioral metrics such as swim speed, depth occupation, swimming direction, and lead-follow interactions demonstrated R. typus individual variation and responses to habitat changes. All sharks displayed increased swim speeds 30-minutes before regimented feed times, when there was scent of food being fed to other animals in the habitat. Consistently in the habitat, one male shark (YU) was recorded swimming more at depth, faster, almost exclusively clockwise, and engaged in fewer close proximity interactions with others than expected by chance. In contrast, a larger female shark (AL) was observed swimming the slowest, at the surface more than others, led other sharks more than she followed, and had strong lead-follow interactions with another shark of the opposite sex (TA). TA and TR did not differ from each other in depth profiles or speed, but did differ in their proclivity to lead or follow. Depth preferences and lead-follow interactions suggest some partitioning of the habitat and the possibility of social hierarchy in this species. These results represent the first longitudinal behavioral analysis of aquarium R. typus, offering meaningful similarities and contrasts to field observations.

The Golden Trevally, Gnathanodon speciosus , is a large predatory fish with an extremely broad tropical Indo-Pacific distribution that crosses many biogeographical boundaries. Both published information and freely available imagery suggest that small juvenile G. speciosus are often associated with whale sharks, Rhincodon typus ; an association that could explain the unusually widespread distribution of G. speciosus , and suggests a novel nursery relationship. The possibility of such an association has the potential to reshape our understanding of the ecological roles played by long-range migrants such as R. typus and other megafauna, our understanding of the full extent of their conservation value, and how we manage both members of the relationship. The Golden Trevally, Gnathanodon speciosus , is a large predatory fish with an extremely broad tropical Indo-Pacific distribution crossing many biogeographical boundaries. Published information and freely available imagery suggest that small juvenile G. speciosus are often associated with whale sharks, Rhincodon typus ; an association that could explain their unusually wide-spread distribution, and suggests a novel nursery relationship. The occurrence of such an association reshapes our understanding of the ecological roles played by long-range migrants such as R. typus and other megafauna. [ABSTRACT FROM AUTHOR]

Simple Summary: Illegal fishing, including that of sharks for meat and fins, is one of the larger threats to marine biodiversity conservation. Getting data on these illegal activities is challenging as there are few reliable official records. I use data from the media, tourists, and artisan fishermen to gain insight into the trade in the world's largest fish, the whale shark, in Indonesia. Whale sharks are typically caught in fishing nets, dragged alongside boats to the shallows, where they are butchered. The meat and oil are sold. In a popular tourist area, Pangandaran, whale sharks are landed and butchered on the beach in view of hundreds of people and local media; I report on 30 landings (2002–2022). Along the south coast of Java, part of which includes Pangandaran, I document 38 landings (2019–2022). Artisanal fishermen see the landings of whale sharks as fortuitous events, and the monetary gains are frequently shared with the community. However, artisanal fisheries pose a significant threat to whale sharks, and the legal protection that whale sharks receive in Indonesia is not sufficiently enforced. Furthermore, Indonesia is a signatory to various international agreements that preclude the fishing and trade in whale sharks, and greater adherence to these rules and regulations is needed. Illegal, unreported, and unregulated fishing, including that of sharks, poses a significant threat to marine ecosystems and individual species. I use data from the media, tourists, and artisan fishermen to gain insight into the trade in the world's largest fish, the whale shark (Rhincodon typus). I focus on the Indonesian island of Java where, along its south coast, whale sharks are landed and butchered on the beach in view of hundreds of people and local media. Whale sharks are typically caught in fishing nets and dragged alongside boats to the shallows, where they are butchered. The meat and oil (valued at ~USD 2000 per shark) are sold and distributed within the community. I document 58 landings of mainly immature whale sharks (2002–2022). Artisanal fishermen see the landing of whale sharks as a fortuitous event, but the species is protected, and Indonesia is a signatory to various international agreements that preclude the fishing of whale sharks. It is imperative for the conservation of whale sharks that the various parties in Indonesia adhere better to their own rules and regulations protecting this species. [ABSTRACT FROM AUTHOR]

Seas and oceans are contaminated by persistent organic pollutants (POPs), which are released into the environment by human activities. The chemical-physical properties of POPs induce high persistence and toxicity in marine organisms from the lowest to the highest trophic levels. Phyto- and zooplankton are at the base of the food chain, and they can adsorb and accumulate these xenobiotic compounds. Therefore, all planktophagous species, including the whale shark (Rhincodon typus), are susceptible to ingesting these contaminants during feeding. From October to December, whale sharks migrate along the north-west coast of Madagascar in search of dense patches of plankton. During scientific expeditions to the whale sharks' foraging areas in the waters of the island of Nosy Be (which is in the north-west of Madagascar), plankton samples were taken. In these samples, the presence and levels of some chlorinated xenobiotics (HCB, DDT and its metabolites, and PCBs) were evaluated in order to estimate the possible impact of whale shark diet on organochlorine (OC) accumulation. The fresh plankton biomass sampled from this region did not seem to be sufficient for the sustenance of the animals, which suggests that the daily contamination input of Rhincodon typus individuals, depending on their plankton diet, is minimal. [ABSTRACT FROM AUTHOR]

The evolution of very large body size requires a ubiquitous and abundant source of food. In marine environments, the largest animals such as whale sharks are secondary consumers that filter feed on nekton, which is plentiful, although patchy. Consequently, feeding in coastal environments requires cost‐efficient foraging that focuses on oceanographic features that aggregate both nektonic prey and marine debris such as floating macroalgae. Consumption of this algae could present an energetic challenge for these animals, unless some component can be digested. Here, we use a multi‐technique approach involving amino acid compound‐specific stable isotope analysis (CSIA) and fatty acid analysis to determine the trophic level of whale sharks and to identify likely items in the diet. CSIA analyses showed that the species has a trophic level consistent with omnivory. Fatty acid profiles of whale shark tissues, feces and potential prey items suggest that the floating macroalgae, Sargassum, and its associated epibionts is a significant source of food. Although this overcomes the energetic challenge of consumption of floating algae, this mode of feeding and the need to focus on oceanographic features that aggregate prey also increases the threat to the species posed by pollutants such as plastic. [ABSTRACT FROM AUTHOR]

The whale shark Rhincodon typus is a broadly distributed and highly mobile planktivorous shark species. The sharks form predictable aggregations in many areas, providing the opportunity for cost‐effective scientific monitoring through divers and other marine resource users. Sightings of individuals outside of these aggregate zones elsewhere in their range are typically rare. We used a citizen science‐based approach to shed light on occurrence and seasonality in the waters around Koh Tao, Thailand and neighbouring islands in the Gulf of Thailand. Although there is a paucity of quantitative data, anecdotal reports suggest substantial declines in sightings in the early 2000s. We identified a total of 178 individual whale sharks (from 249 sightings) between 2004 and 2019, with most of these (84%) from the 2015–2019 time period due to an increase in sighting reports facilitated by social media and direct marketing. Size estimates were reported for 102 of the sightings, with a range of 2–6 m and mean of 3.7 m overall. Sex was reported for 27% of sightings, with a 2:1 female‐to‐male ratio. Modified maximum likelihood methods suggest whale sharks are transient to Koh Tao and surrounding areas, with whale shark sightings following the regional monsoon cycle. One international resighting was obtained from Malaysian waters (~700 km away). Encouraging citizen science participation is particularly useful in data‐poor regions like the Gulf of Thailand, despite limitations in size and sex estimation reliability, which can play an important complementary role in dedicated research programs. [ABSTRACT FROM AUTHOR]

Measurements obtained from aerial imagery can be used to calculate body shape, condition and growth rates of large surface-associated marine megafauna. In this study, an unoccupied aerial vehicle (UAV) was used to obtain aerial images of an elasmobranch species, the whale shark (Rhincodon typus). Pre-caudal length (PCL) and multiple body width measurements were taken from aerial images of 26 juvenile whale sharks, obtained between November 2020 and February 2021 in the La Paz Bay, Mexico. PCL ranged from 2.98 to 6.43 m, with a mean of 4.93 m (SD = 1.00). Body width was found to be greatest in the region by the snout and anterior contacts of the pectoral fins. Body width decreased in a near-linear manner from ~ 18% PCL at the midpoint to ~ 10% PCL at the posterior end of the body. There was a significant linear relationship between whale shark dorsal surface area (SA) and PCL on the log–log scale (LM: F1,24 = 647.7, P < 0.001), showing that whale sharks increase exponentially in overall body size as they increase in body length. However, there was no effect of PCL on the relative body width at the different measurement sites, suggesting that body shape of whale sharks was similar across the size range measured in this study. Finally, the body condition of the sharks, measured as the residual of the relationship between SA and PCL, varied between − 21.6% and + 14.0%. This study highlights the benefits of using UAV photogrammetry to measure large marine fauna, to obtain valuable morphometric data to study their physiology and bioenergetics. [ABSTRACT FROM AUTHOR]

The world’s largest extant fish, the whale shark Rhincodon typus, is one of the most-studied species of sharks globally. The discovery of predictable aggregation sites where these animals gather seasonally or are sighted year-round – most of which are coastal and juvenile-dominated – has allowed for a rapid expansion of research on this species. The most common method for studying whale sharks at these sites is photographic identification (photo-ID). This technique allows for long-term individual-based data to be collected which can, in turn, be used to evaluate population structure, build population models, identify long-distance movements, and assess philopatry and other population dynamics. Lagged identification rate (LIR) models have fewer underlying assumptions than more traditional capture mark recapture approaches, making them more broadly applicable to marine taxa, especially far-ranging megafauna species like whale sharks. However, the increased flexibility comes at a cost. Parameter estimations based on LIR can be difficult to interpret and may not be comparable between areas with different sampling regimes. Using a unique data-set from the Philippines with ~8 years of nearly continuous survey effort, we were able to derive a metric for converting LIR residency estimates into more intuitive days-per-year units. We applied this metric to 25 different sites allowing for the first quantitatively-meaningful comparison of sightings-derived residence among the world’s whale shark aggregations. We validated these results against the only three published acoustic residence metrics (falling within the ranges established by these earlier works in all cases). The results were then used to understand residency behaviours exhibited by the sharks at each site. The adjusted residency metric is an improvement to LIR-based population modelling, already one of the most widely used tools for describing whale shark aggregations. The standardised methods presented here can serve as a valuable tool for assessing residency patterns of whale sharks, which is crucial for tailored conservation action, and can cautiously be tested in other taxa.

Whale sharks (Rhincodon typus) are found circumglobally in tropical, subtropical, and warm temperate waters, and their known seasonal aggregations and migratory movements are influenced by factors such as ocean currents, thermobiological systems, and patterns of productivity. Several locations in the eastern tropical Pacific Ocean are known habitats for R. typus; Although it has long been known that whale sharks aggregate along the Panama coast, little is known in relation to their movement patterns, behavior, and habitat use. In this study, we investigated the movements and behaviors of R. typus tagged in Panama in relation to oceanographic variables and examined the overlap of foraging habitat and migratory routes with marine protected areas (MPAs), industrial fishing areas, and marine traffic. Satellite tracks from 30 R. typus tagged in the coastal waters of Panama were examined, including nine tags suspicious of earlier detachment. A hidden Markov model was then used to identify different behavioral states (foraging and migrating) and their relationships with environmental variables (sea surface temperature, primary productivity, chlorophyll-a concentrations, and eddy location/speed) Tracks were also superimposed on maps of MPAs, industrial fishing areas, and regional marine vessel traffic to identify the degree of overlap. Rhincodon typus foraged mainly within the Panamanian exclusive economic zone but also moved north and south along the coast and out to the open ocean. Significant differences in environmental conditions were found between sites in which foraging and migrating behaviors were recorded. Higher productivity and chlorophyl concentration were associated with foraging behavior, while higher eddy speeds were observed when sharks migrated. Rhincodon typus used MPAs; however, there was a high degree of overlap between their habitat and areas of industrial fishing and marine vessel traffic. Our results highlight the use of the coastal waters of Panama, oceanic seamounts, and ridges, MPAs and industrial fishing areas by R. typus for foraging and migration. Additionally, our findings highlight the importance of satellite tracking studies for understanding the behavior and habitat use of highly mobile migratory species, such as R. typus.

Whale sharks are known to aggregate in coastal areas. In the South Ari Marine Protected Area (Maldives) a aggregation, mostly represented by young males with a high level of residency, has been described in the literature. Despite the worldwide interest in the natural resources of the Maldives, this population is increasingly subjected to anthropogenic pressure and major concern regards the flourishing tourist industry. In this study, data collected by the Maldives Whale Shark Research Programme between 2014 and 2017 have been used to detect both temporal and spatial patterns of occurrence. Favourable environmental conditions to visually detect whale sharks have been defined for the studied area. Accordingly, a total of 1077 shark encounters have been analysed in this study. Environmental conditions (i.e. sea surface temperature, monsoon occurrence) have been used to detect possible factors affecting the spatial and temporal variability of Rhincodon typus aggregations. A two-way ANOVA has been performed to detect temporal trends in animal occurrence, sea surface temperature pattern and to investigate the sea bottom depth variability during encounters. Significant differences in the monthly occurrence of whale sharks within the same year and among different years have been detected. Similar patterns have been observed for environmental parameters such as sea surface temperature and depth. A different spatial distribution has also been detected as a function of the Indian Monsoon reversal (north-eastern and south-western) affecting the area. During the northeast monsoon period, whale sharks appeared to concentrate in a smaller longitudinal range closer to the western-central part of the MPA, where deeper water conditions occur due to the proximity of a deep depression (submarine canyon). Results from this study provide new pieces of information for the implementation of dedicated management actions to protect the whale sharks population inhabiting the South Ari Marine Protected Area.

Rhincodon typus is a keystone and indicator species in marine ecosystems. Meanwhile, R. typus has been listed on the IUCN red list of vulnerable species. Here we used ONT platform to determine the full-length (FL) transcriptome of R. typus and obtained 14,930 FL transcripts. Among all FL transcripts, 14,915 transcripts were covered 11,892 genetic loci and 1,642 novel genetic loci were further found. Meanwhile, we identified 714 novel transcripts by compared FL transcripts with the R. typus genome. Based on FL transcripts, we also predicted the distribution patterns of ASs, LncRNAs, polyAs, CDSs and methylation sites on FL transcriptome of R. typus. Furthermore, a total of 31,021 (97.86%) CDSs can obtained annotation information. Overall, our work firstly provided the FL transcriptome and these sequences complete the annotated R. typus genome information. Furthermore, these information are a potential resource to study biological processes of R. typus.

Abstract The whale shark Rhincodon typus is found throughout the world's tropical and warm‐temperate ocean basins. Despite their broad physical distribution, research on the species has been concentrated at a few aggregation sites. Comparing DNA sequences from sharks at different sites can provide a demographically neutral understanding of the whale shark's global ecology. Here, we created genetic profiles for 84 whale sharks from the Saudi Arabian Red Sea and 72 individuals from the coast of Tanzania using a combination of microsatellite and mitochondrial sequences. These two sites, separated by approximately 4500 km (shortest over‐water distance), exhibit markedly different population demographics and behavioral ecologies. Eleven microsatellite DNA markers revealed that the two aggregation sites have similar levels of allelic richness and appear to be derived from the same source population. We sequenced the mitochondrial control region to produce multiple global haplotype networks (based on different alignment methodologies) that were broadly similar to each other in terms of population structure but suggested different demographic histories. Data from both microsatellite and mitochondrial markers demonstrated the stability of genetic diversity within the Saudi Arabian aggregation site throughout the sampling period. These results contrast previously measured declines in diversity at Ningaloo Reef, Western Australia. Mapping the geographic distribution of whale shark lineages provides insight into the species’ connectivity and can be used to direct management efforts at both local and global scales. Similarly, understanding historical fluctuations in whale shark abundance provides a baseline by which to assess current trends. Continued development of new sequencing methods and the incorporation of genomic data could lead to considerable advances in the scientific understanding of whale shark population ecology and corresponding improvements to conservation policy.

The whale shark Rhincodon typus is found throughout the world's tropical and warm‐temperate ocean basins. Despite their broad physical distribution, research on the species has been concentrated at a few aggregation sites. Comparing DNA sequences from sharks at different sites can provide a demographically neutral understanding of the whale shark's global ecology. Here, we created genetic profiles for 84 whale sharks from the Saudi Arabian Red Sea and 72 individuals from the coast of Tanzania using a combination of microsatellite and mitochondrial sequences. These two sites, separated by approximately 4500 km (shortest over‐water distance), exhibit markedly different population demographics and behavioral ecologies. Eleven microsatellite DNA markers revealed that the two aggregation sites have similar levels of allelic richness and appear to be derived from the same source population. We sequenced the mitochondrial control region to produce multiple global haplotype networks (based on different alignment methodologies) that were broadly similar to each other in terms of population structure but suggested different demographic histories. Data from both microsatellite and mitochondrial markers demonstrated the stability of genetic diversity within the Saudi Arabian aggregation site throughout the sampling period. These results contrast previously measured declines in diversity at Ningaloo Reef, Western Australia. Mapping the geographic distribution of whale shark lineages provides insight into the species' connectivity and can be used to direct management efforts at both local and global scales. Similarly, understanding historical fluctuations in whale shark abundance provides a baseline by which to assess current trends. Continued development of new sequencing methods and the incorporation of genomic data could lead to considerable advances in the scientific understanding of whale shark population ecology and corresponding improvements to conservation policy. [ABSTRACT FROM AUTHOR]

Whale sharks are known to aggregate in coastal areas. In the South Ari Marine Protected Area (Maldives) a aggregation, mostly represented by young males with a high level of residency, has been described in the literature. Despite the worldwide interest in the natural resources of the Maldives, this population is increasingly subjected to anthropogenic pressure and major concern regards the flourishing tourist industry. In this study, data collected by the Maldives Whale Shark Research Programme between 2014 and 2017 have been used to detect both temporal and spatial patterns of occurrence. Favourable environmental conditions to visually detect whale sharks have been defined for the studied area. Accordingly, a total of 1077 shark encounters have been analysed in this study. Environmental conditions (i.e. sea surface temperature, monsoon occurrence) have been used to detect possible factors affecting the spatial and temporal variability of Rhincodon typus aggregations. A two-way ANOVA has been performed to detect temporal trends in animal occurrence, sea surface temperature pattern and to investigate the sea bottom depth variability during encounters. Significant differences in the monthly occurrence of whale sharks within the same year and among different years have been detected. Similar patterns have been observed for environmental parameters such as sea surface temperature and depth. A different spatial distribution has also been detected as a function of the Indian Monsoon reversal (north-eastern and south-western) affecting the area. During the northeast monsoon period, whale sharks appeared to concentrate in a smaller longitudinal range closer to the western-central part of the MPA, where deeper water conditions occur due to the proximity of a deep depression (submarine canyon). Results from this study provide new pieces of information for the implementation of dedicated management actions to protect the whale sharks population inhabiting the South Ari Marine Protected Area. [ABSTRACT FROM AUTHOR]

Between September and December, whale sharks (Rhincodon typus) aggregate in the coastal waters off Nosy Be, an island in north‐western Madagascar. Swimming with these sharks has become an important tourism activity, but no formal protection is in place in Madagascar to protect this endangered species from the potential negative effects of tourism or other human impacts.Boat‐based surveys (n = 405) were conducted from tourism vessels from September to December, 2015–2019. For most sightings (98%), whale sharks were sighted while foraging for bait fish at the surface, in association with mackerel tuna (Euthynnus affinis) and seabirds (Sternidae). A total of 408 individual whale sharks were individually photo‐identified over this period. All individuals were immature, and 82% of sexed sharks were male. Sharks ranged from 3.0 to 8.0 m in total length (TL), with a mean TL of 5.65 ± 0.94 m (n = 66) for females and 5.46 ± 1.09 m for males (n = 295).Most sharks (72% of the identified individuals) were only identified once within the study period. Movement modelling showed an open population with a short mean residence time of 7.2 days. Resightings were recorded from up to 12 years apart (2007–2019). Ten sharks were seen in all five seasons during 2015–2019. A basic POPAN mark–recapture model estimated a total population size of 681 (608–763) sharks over the 2015–2019 period.Nosy Be waters are an important foraging ground for juvenile whale sharks. Sighting data demonstrate that a high proportion of the sharks' preferred habitat lies outside existing protected areas, but within an identified Key Biodiversity Area. National species‐level protection and increased spatial management is warranted to secure the continued presence of whale sharks in this region. [ABSTRACT FROM AUTHOR]

The whale shark (Rhincodon typus) is an endangered and highly migratory species, of which solitary individuals or aggregations are observed in oceans worldwide and for which conservation efforts are hindered by a lack of comprehensive data on genetic population connectivity. Tissue samples were collected from wandering whale sharks in Pacific Panama to determine genetic diversity, phylogeographic origin, and possible global and local connectivity patterns using a 700–800 bp fragment of the mitochondrial control region gene. Genetic diversity among samples was high, with five new haplotypes and nine polymorphic sites identified among the 15 sequences. Haplotype diversity (Hd = 0.83) and nucleotide diversity (π = 0.00516) were similar to those reported in other studies. Our sequences, in particular haplotypes PTY1 and PTY2, were similar to those previously reported in the Arabian Gulf and the Western Indian Ocean populations (a novel occurrence in the latter case). Haplotypes PTY3, PTY4, and PTY5 were similar to populations in Mexico and the Gulf of California. In contrast, the only populations to which our Panamanian sequences were genetically dissimilar were those from the Atlantic Ocean. The absence of reference sequences in GenBank from southern sites in the Eastern Tropical Pacific, such as Galapagos (Ecuador), Gorgona and Malpelo Islands (Colombia), and Coco Island (Costa Rica), reduced our capacity to genetically define regional patterns. Genetic differentiation and connectivity were also assessed using an analysis of molecular variance (AMOVA), which showed a similar population structure (five groups) to the neighbor-joining tree. Other population features based on neutrality tests, such as Tajima’s D and Fu’s Fs statistics, showed positive values for Panama of 0.79 and 1.61, respectively. Positive values of these statistics indicate a lack of evidence for population expansion among the sampled individuals. Our results agree with previous reports suggesting that whale sharks can travel over long distances and that transboundary conservation measures may be effective for species protection.

The aim of this study is to provide preliminary observations on the microanatomy of Rhincodon typus skin using histology and electron microscopy analyses. Skin biopsies were obtained from a deceased juvenile male shark (548 cm total length) stranded in La Paz, Mexico, during February 2018. The results of this study evidenced the basic structure of the dermal denticles in the epidermis of the trunk of the shark, as well as the composition of the connective tissue in the hypodermis. Histological images of the hypodermis showed a high concentration of collagen fibres, formed by a large number of fine and wavy fibres of compact shape and little intercellular substance. [ABSTRACT FROM AUTHOR]

Whale sharks are known to feed primarily on zooplankton all over the world; however, recent findings suggest that they also prey on fish using behaviors that have not been fully described. Here, we provide detailed evidence of whale sharks interacting with schools of anchovy on four occasions in Bahia de Los Angeles, Baja California, Mexico. Three of these were predatory interactions in multi-species feeding frenzies, and one was a non-predatory interaction. In predatory interactions, whale sharks exhibited two types of feeding behaviors: (1) stationary suction-feeding, a previously described behavior for whale sharks, and (2) lunge-feeding, which has not been previously described in whale sharks, but has been observed among other large filter feeders, such as rorqual whales. The whale sharks moved simultaneously around the school of anchovy, lunging simultaneously or one after another into the school, with 66% (N = 17) of these lunges occurring in the same direction. In the non-predatory interaction, whale sharks exhibited "sit-and-wait" behavior. The evidence presented here, along with previous observations, suggests that whale sharks may change their feeding strategy from suction to lunge-feeding when other predators corner schooling fish. [ABSTRACT FROM AUTHOR]

Chondrichthyes (cartilaginous fishes) are fundamental for understanding vertebrate evolution, yet their genomes are understudied. We report long-read sequencing of the whale shark genome to generate the best gapless chondrichthyan genome assembly yet with higher contig contiguity than all other cartilaginous fish genomes, and studied vertebrate genomic evolution of ancestral gene families, immunity, and gigantism. We found a major increase in gene families at the origin of gnathostomes (jawed vertebrates) independent of their genome duplication. We studied vertebrate pathogen recognition receptors (PRRs), which are key in initiating innate immune defense, and found diverse patterns of gene family evolution, demonstrating that adaptive immunity in gnathostomes did not fully displace germline-encoded PRR innovation. We also discovered a new toll-like receptor (TLR29) and three NOD1 copies in the whale shark. We found chondrichthyan and giant vertebrate genomes had decreased substitution rates compared to other vertebrates, but gene family expansion rates varied among vertebrate giants, suggesting substitution and expansion rates of gene families are decoupled in vertebrate genomes. Finally, we found gene families that shifted in expansion rate in vertebrate giants were enriched for human cancer-related genes, consistent with gigantism requiring adaptations to suppress cancer.

The Gulf of California represents an important hotspot for whale shark (Rhincodon typus) aggregation. Anthropogenic activities and natural sources could expose sharks to high levels of trace elements (TEs). To determinate these levels in this endangered species, concentrations of As, Cd, Cu, Pb and Zn (in ng/g ww) were measured in 130 whale shark skin biopsies and 44 zooplankton samples collected from two areas of the Gulf of California, Bahía de Los Angeles (BLA) and Bahía de La Paz (LAP) during 2016–2018. For biopsies, Zn exhibited highest concentrations in BLA (2016–2017, 298 ± 406; 2017–2018, 1959 ± 2545) and at LAP (in 2016–2017, 595 ± 554; in 2017–2018, 2642 ± 1261). On the other hand, Cd (BLA 2016–2017, 3 ± 3; LAP 2016–2017, 4 ± 3; BLA 2017–2018, 17 ± 14; LAP 2017–2018, 13 ± 10) and Pb (BLA 2016–2017, 7 ± 7; LAP 2016–2017, 15 ± 32; BLA 2017–2018, 69 ± 76; LAP 2017–2018, 7 ± 5) showed lowest concentrations. Significant differences in TE concentrations between sites and periods occurred. Arsenic found in shark biopsies from La Paz suggested enrichment and/or increased bioavailability in this area. Sex alone was not a significant factor in TE concentration; nevertheless, a sex-dependent difference in correlation of TE concentration and size was noted (negative in males, positive in females). This indicates feeding strategies of whale shark may be sex and size segregated. During 2017–2018, zooplankton and sharks showed enrichment in all TEs. Essential elements were not biomagnified by sharks. Lead was biomagnified through zooplankton. Strong positive correlation between selected elements indicates that Zn, Cd and Pb follow the same metabolic route in the sharks' body. [ABSTRACT FROM AUTHOR]

A basic tenet of ecotourism is to enhance conservation. However, few studies have assessed its effectiveness in meeting conservation goals and whether the type of tourism activity affects outcomes. This study examines whether working in ecotourism changes the perceptions of and attitudes and behaviours of local people towards the focal species and its habitat and, if so, if tourism type affects those outcomes. We interviewed 114 respondents at four whale shark Rhincodon typus tourism sites in the Philippines to compare changes in perceptions of and attitudes and behaviours towards whale sharks and the wider marine environment. We found that the smaller scale tourism sites had greater social conservation outcomes than the mass or failed tourism sites, including changes in conservation ethics and perceptions of and attitudes and behaviours towards whale sharks and the ocean. Furthermore, of the three active tourism sites, the smallest site, with the lowest economic returns and the highest negative impacts on whale sharks prior to tourism activities, had the largest proportion of respondents who reported a positive change in perceptions of and attitudes and behaviours towards whale sharks and the ocean. Our results suggest that tourism type, and the associated incentives, can have a significant effect on conservation outcomes and ultimately on the ecological status of an Endangered species and its habitat. [ABSTRACT FROM AUTHOR]

Trace elements were determined in three areas of the right (RL) and left (LL) lobe of the liver obtained from a whale shark (Rhincodon typus) stranded in Mexico. Mean ± standard error concentrations in µg g-1 wet weight were for zinc (Zn) RL: 22.5 ± 2.1; LL: 26.5 ± 7.1, arsenic (As) RL: 33.0 ± 1.6; LL: 20.0 ± 9.9 and cadmium (Cd) RL: 15.5 ± 0.9; LL: 11.3 ± 3.7; copper (Cu) RL: 3.2 ± 0.3; LL: 2.2 ± 0.8, selenium (Se) RL: 0.5 ± 0.1; LL: 1.2 ± 0.6, mercury (Hg) RL: 0.06 ± 0.02; LL: 0.05 ± 0.004 and lead (Pb) RL: 0.05 ± 0.02; LL: 0.05 ± 0.01. Concentrations showed significant (P < 0.05) differences within the same lobe but not between lobes. The trace element levels found in this whale shark represent the baseline levels of the trophic base's health status in the study area. [ABSTRACT FROM AUTHOR]

Age and growth data are central to management or conservation strategies for any species. Circumstantial evidence suggests that male whale sharks (Rhincodon typus) grow to asymptotic sizes much smaller than those predicted by age and growth studies and consequently, there may be sex-specific size and growth patterns in the species. We tested this hypothesis by using stereo-video and photo-identification studies to estimate the growth rates of 54 whale sharks that were resighted over a period of up to a decade at Ningaloo Reef. We found that male growth patterns were consistent with an average asymptotic total length (TL) of approximately 8–9 m, a size similar to direct observations of size at maturity at aggregation sites world-wide and much smaller than the sizes predicted by earlier modeling studies. Females were predicted to grow to an average asymptotic length of around 14.5 m. Males had growth coefficients of K = 0.088 year–1, whereas limited resighting data suggested a growth coefficient of K = 0.035 year–1 for females. Other data including re-sightings of an individual male over two decades, records of sex-specific maximum sizes of individuals captured in fisheries and data from juveniles growing in aquaria were also consistent with the suggestion of sex-specific growth profiles for the species. We argue that selection for sex-specific growth patterns could explain many of the otherwise enigmatic patterns in the ecology of this species including the tendency of the species to form aggregations of juvenile males in coastal waters.

Highly mobile marine megafauna species, while widely distributed and frequently threatened, often aggregate in distinct localized habitats. Implementation of local management initiatives within these hotspots is more achievable than developing effective conservation strategies that encompass their entire distributions. Such measures have the potential for disproportionate population-level benefits but rely on a detailed understanding of spatiotemporal habitat use. To that end, we examined the residency and small-scale habitat use of 51 whale sharks (Rhincodon typus) over 5 years at an aggregation site in Tanzania using passive acoustic telemetry. Whale sharks were highly resident within and across years, with a combined maximum residency index of 0.39. Although fewer sharks were detected from March to September, residency was high throughout the year. Ancillary photographic-identification data showed that individual residency persisted before and after tag attachment. Kernel utilization distributions (KUD) and movement networks both revealed the same spatiotemporal pattern of habitat use, with a small core habitat (50% KUD area for all sharks combined = 12.99 km2) that predictably changed on a seasonal basis. Activity spaces did not differ with time of day, sex, or size of the sharks, indicating a population-level pattern driven by prey availability. The small and predictable core habitat area at this site means that site-based management options to reduce shark injuries and mortality from boat strike and fishing gear entanglement can be spatially targeted for maximum effectiveness and compliance by human users.

The whale shark is a globally endangered species that is distributed in tropical and warm temperate waters. This study modeled the present-day and future habitat suitability of this species in the Sunda tectonic plate region in Southeast Asia to identify changes and highlight potential areas for conservation. Presence data from the International Union for Conservation of Nature were combined with six environment variables to model habitat suitability under three climate change scenarios. The present-day model results showed that most areas of high suitability matched the occurrence data. The future models generated revealed a small decrease in habitat suitability on the Sunda plate. In all of the three future models, two areas of high suitability were predicted: the central islands of the Philippines and southern Thailand. Areas of high suitability remained the same in the parts of the Gulf of Thailand, southern Indonesia, and the central islands of the Philippines. Based on this information, suggestions on how to protect the environment in these areas were made, including a regional assessment of the whale shark status and implementing a species recovery plan in Southeast Asia. [ABSTRACT FROM AUTHOR]

Within the Gulf of Aden, Djibouti is an important site where whale sharks (Rhincodon typus Smith 1828) aggregate seasonally; however, up to now, only few studies have been carried out in the area (Rowat et al. in Environ Biol Fishes, 2007. 10.1007/s10641-006-9148-7; Mar Freshw Res, 2011. 10.1071/MF10135; Rezzolla and Storai in Cybium 34:195–206, 2010). From 2015 to 2018, whale shark photo-id, skin biopsies, and zooplankton samples were collected to investigate the ecology of this species in Djibouti. Of the 190 photo-identified individuals, the majority were juvenile males, confirming a significant male-based aggregation (X2 = 65, df = 1, p < 0.0001). Within each season, the maximum number of times an individual was re-sighted was 11, while the inter-annual re-sighting rates varied between 11 and 32%. Animals were feeding on surface zooplankton, consisting primarily of copepods (85%); however, Chaetognatha and Ctenophora appeared to be important taxa as well, since the areas most visited were also those with higher concentration of these organisms. Feeding zooplankton patches had a mean biomass of 42.2 ± 31.9 mg m−3, almost 1.5 higher than control stations, indicating that the abundance of this species was positively related to food availability. Furthermore, whale sharks exhibited a clear temporal distribution associated with the variation in zooplankton biomass due to the monsoon winds. Sharks aggregated in October–February, with a peak in sightings in November, and dispersed outside the upwelling season. δ13C values suggested that whale sharks might migrate to other habitats or shift their activities to deeper areas outside the aggregation phase. Little intra-specific variation in δ15N and δ13C was found between animals, suggesting a similar habitat use. [ABSTRACT FROM AUTHOR]

The present observation illustrates about the incidental sighting of the whale shark, Rhincodon typus (Smith, 1828) on 16th January 2018 in the coastal waters of Goa (15°47.086΄ N; 073°05.120΄ E) at a depth zone of about 74 m onboard the research vessel FORV Sagar Sampada during the cruise No. 370. The sightings were confirmed by visuals in real-time and photographs. This individual was characterized by pale yellow or white rounded to elongated spots on a dark grey background. Satellite-derived oceanographic parameters such as Sea Surface Temperature (SST), Sea Surface Salinity (SSS) and Chlorophyll ‘a’, (Chl-a) for the location where the animal was recorded, have shown different patterns from rest of the area and thus provided an insight into the preferred environmental conditions and foraging behavior of this species. The sighting location, off the Goa coast, was characterized by high Chlorophyll-a (1.2-1.8 mg/m-3), dissolved oxygen (4 ml/l) in the 50 m depth and high concentrations of phytoplankton dominated by green Noctiluca scintillans. Present sighting merit the record of R. typus with the probability of foraging on the high abundance of phytoplankton in the coastal waters of the Arabian Sea. Therefore, the animal appeared to move along the gradient zones for its seasonal aggregations. [ABSTRACT FROM AUTHOR]

Tourists approaching wild animals can potentially cause disturbance as a result of the perceived predation risk. Risk effects arise when prey alter their behaviour in response to predators. This response may carry costs through its impact on fitness-related activities such as foraging. We recorded behavioural responses of whale sharks Rhincodon typus to experimental vessel and swimmer approaches. We simulated the disturbance caused by ecotourism in the foraging site of this planktivorous fish in Bahia de Los Angeles, Gulf of Baja California, Mexico. Stress-related behaviours (vigilance, change of direction, diving and acceleration) were more common directly after both types of disturbance than before, in particular after approach by a swimmer. Individuals were more likely to be vigilant when they were new to the bay, but we did not find evidence of within-season behavioural habituation. Sharks were 24% more likely to forage before human stimuli than after. Our study highlights negative effects of vessel and swimmer approaches on whale shark behaviour, with a short-term increase in stress-related behaviours potentially carrying energetic costs, combined with a decrease in food intake following the disturbance. Our results indicate concerns about the impact of ecotourism on large fish species. An important next step would be to determine whether these short-term behavioural responses to the perception of predation risk negatively affect fitness. Among other guidelines, we recommend preventing swimmers from approaching if whale sharks stop feeding when a vessel approaches. [ABSTRACT FROM AUTHOR]

The present study was based on sighting of whale shark, Rhincodon typus Smith, 1828 on 13th and 14th October 2016 incidentally in oceanic waters of Bay of Bengal at a depth of 3340 and 3270 m. These two sightings were thus confirmed by photographs. Whale sharks were reported in the coastal and near shore regions of India by many of the researchers and this is the first observation of R. typus in oceanic waters of east coast of India.

Abstract Background The whale shark (Rhincodon typus) has by far the largest body size of any elasmobranch (shark or ray) species. Therefore, it is also the largest extant species of the paraphyletic assemblage commonly referred to as fishes. As both a phenotypic extreme and a member of the group Chondrichthyes – the sister group to the remaining gnathostomes, which includes all tetrapods and therefore also humans – its genome is of substantial comparative interest. Whale sharks are also listed as an endangered species on the International Union for Conservation of Nature’s Red List of threatened species and are of growing popularity as both a target of ecotourism and as a charismatic conservation ambassador for the pelagic ecosystem. A genome map for this species would aid in defining effective conservation units and understanding global population structure. Results We characterised the nuclear genome of the whale shark using next generation sequencing (454, Illumina) and de novo assembly and annotation methods, based on material collected from the Georgia Aquarium. The data set consisted of 878,654,233 reads, which yielded a draft assembly of 1,213,200 contigs and 997,976 scaffolds. The estimated genome size was 3.44Gb. As expected, the proteome of the whale shark was most closely related to the only other complete genome of a cartilaginous fish, the holocephalan elephant shark. The whale shark contained a novel Toll-like-receptor (TLR) protein with sequence similarity to both the TLR4 and TLR13 proteins of mammals and TLR21 of teleosts. The data are publicly available on GenBank, FigShare, and from the NCBI Short Read Archive under accession number SRP044374. Conclusions This represents the first shotgun elasmobranch genome and will aid studies of molecular systematics, biogeography, genetic differentiation, and conservation genetics in this and other shark species, as well as providing comparative data for studies of evolutionary biology and immunology across the jawed vertebrate lineages.

The implications of plastic pollution, including microplastics, on marine ecosystems and species are increasingly seen as an environmental disaster. Yet few reports focus on filter-feeding megafauna in regions heavily impacted by plastic pollution, such as Indonesia in the Coral Triangle, a global marine biodiversity hotspot. Here, we evaluate plastic abundance and characterize debris from feeding grounds for manta rays Mobula alfredi and whale sharks Rhincodon typus in three coastal locations in Indonesia: Nusa Penida Marine Protected Area, Komodo National Park, and Pantai Bentar, East Java. A 200 μm plankton net was used to sample the top 0.5 m of the water column (‘trawl survey’) and floating plastics were assessed along ∼440 m long transects (‘visual survey’) during the Indonesian north-west (wet) and south-east (dry) monsoon seasons during 2016–2018. Microplastics were identified visually, measured and categorized from trawl samples, and larger floating plastics were counted and categorized visually from boats. Plastic abundance ranged widely from 0.04 to 0.90 pieces m–3 (trawl survey) and 210 to 40,844 pieces km–2 (visual survey). Results from linear models showed significant seasonal and location differences in estimated plastic abundance for trawl and visual surveys in Nusa Penida and Komodo. Plastic abundance was up to ∼ 44 times higher in the wet than the dry season, with the largest seasonal effect observed in Nusa Penida. Overall, small pieces 50% combined) were the most prevalent plastics. Theoretical plastic ingestion rates were calculated using estimated filtration volumes of manta rays and whale sharks and the mean plastic abundance in their feeding grounds. Upper plastic ingestion estimates for manta rays were ∼63 and 25 pieces h–1 for Nusa Penida and Komodo locations, respectively, and ∼137 pieces h–1 for whale sharks in Java. Analysis of manta ray egested material confirmed plastic ingestion, the consequences of which might include exposure to toxic plastic additives and adhered persistent organic pollutants. Communicating this information to communities who stand to benefit from healthy megafauna populations might help local governments as they work toward reducing plastics in the marine environment.

The genetic population structure and demographic history of the whale shark Rhincodon typus , including 28 samples around Japan, the northernmost limit of distribution of the species, were examined based on partial sequences of the mitochondrial control region. Neighbor-joining tree and the minimum spanning network of haplotypes showed no clear phylogeographic structure. The pairwise ΦST values between each of the nine localities in the Indo-Pacific and the locality in the Atlantic were very high and significant, indicating the existence of genetic differentiation between the Indo-Pacific and the Atlantic. The existence of some level of genetic differentiation was also suggested between the Indian and the eastern Pacific, because the ΦST values were significant (though before Bonferroni correction) when comparing the Gulf of California in the eastern Pacific with three of the six localities in the Indian Ocean. In the Pacific Ocean, none of the ΦST values among the three localities (the Philippines and Taiwan, Japan, and Gulf of California) were significant, which indicates that migrations occur between the eastern and the western North Pacific as well as between north and south in the western North Pacific. The mismatch distributions and Bayesian skyline plots suggested that the Indo-Pacific and the Atlantic populations have different demographic history; population expansion had occurred in the Indo-Pacific while secondary contact among differentiated lineages was indicated in the Atlantic. Global distribution of effective population size (N e) of the whale shark was estimated to be 63% in the Indo-Pacific and 37% in the Atlantic. [ABSTRACT FROM AUTHOR]

In-water shark-based tourism is growing worldwide and whale sharks (Rhincodon typus) are one of the most popular targets of this industry. It is important to monitor tourism industries to minimize any potential impacts on target species. At Ningaloo, Western Australia, Electronic Monitoring Systems (EMS) have been installed on licensed tour vessels to collect information on encounters between snorkelers and whale sharks. This study combined data from the EMS with whale shark identification photographs, to assess the impact of in-water tourism on the encounter duration for individual sharks. During 2011 and 2012, 948 encounters with 229 individual sharks were recorded using EMS. Encounter durations between whale sharks and tourism vessels ranged between 1 and 59 min (mean = 11 min 42 s, SD = ±11 min 19 s). We found no evidence for a decline in encounter duration after repeated tourist encounters with individual sharks. Encounter duration varied among tourism operator vessels and were shorter when the sex of the whale shark could not be identified. Given that individual sharks were swum with on average 2.4 times per day (± SD 2.08), and up to 16 times over the course of the study, our results suggest that there is no evidence of long-term impacts of tourism on the whale sharks at Ningaloo. However, the inclusion of well-defined categories of whale shark behaviors and information regarding how interactions between tourists and whale sharks end will complement the data already collected by the EMS. This preliminary investigation demonstrates the potential for the EMS as a data resource to better understand and monitor the impacts of tourism interactions on whale sharks. [ABSTRACT FROM AUTHOR]

This paper is the first report with morphometric measurements in the Eastern Tropical Pacific of a deceased 5.48 m juvenile whale shark Rhincodon typus, from a rare stranding in La Paz Bay in the Gulf of California, Mexico. Biological measurements and age estimation are provided by the analysis of photographs and growth in rings from vertebrae. [ABSTRACT FROM AUTHOR]

Abstract Marine litter has adversely affected many marine species. However, information on its impacts on filter-feeding elasmobranchs (such as the whale shark, Rhinocodon typus) is scarce. The Philippines is an essential habitat for whale sharks, and the lack of data on marine litter and its effects on these organisms in the country is concerning. Beached carcasses present opportunities to provide useful data and insights on the issue. On the 7th August 2018, a live whale shark was found beached in Tagum City, the Philippines, and it eventually died. As part of the post-mortem examination, the gastrointestinal tract and gills of the specimen were examined. Marine litter was found lodged in its gills, and pieces of plastic were found inside its stomach (including several pieces likely from local sources within the Philippines). This study is the first documentation of litter in whale sharks from the Philippines, confirming their vulnerability to marine litter. Highlights • First evidence of marine litter ingestion by a whale shark (Rhincodon typus) from the Philippines. • Marine litter may have been ingested locally or ingestion occurred near the source of the litter. • Provide baseline data for future studies on marine litter ingestion by whale sharks. [ABSTRACT FROM AUTHOR]

Donsol in the Philippines is the longest running community-based whale shark (Rhincodon typus) ecotourism site in Southeast Asia, with peak visitation in 2012 of over 27,000 tourists. In order to understand this aggregation and the importance of the area to whale sharks, dedicated photographic identification (photo-ID) research began in 2007. In-water photo-ID surveys were conducted from tourism boats, weather and operator permitting, from December to June between 2007 and 2016. Visual matches of the unique spot patterns of each individual shark were validated by the pattern-recognition software Interactive Individual Identification System (I3S), and on the online database Wildbook for Whale Sharks (www.whaleshark.org). A total of 1,985 photo-ID trips over 895 survey days resulted in 6,786 encounters with R. typus. Combined with encounters from both dedicated research and citizen science dating back to 1998, 479 individual whale sharks were identified, making up 44% of the known whale shark population in the Philippines (n = 1,095). Of these, photographs of the pelvic region confirmed the sex for 158 males and 22 females. Visual size estimates ranged from 2 to 10 m (mean ± SD = 6.5 ± 1.6 m). Maturity in males (LT50) was estimated at 6.8 ± 0.2 m total length, with 53% of males considered mature. Annually, the total number of individuals sighted varied between 15 and 185 (mean ± SD = 104 ± 55.53), with a recruitment of 3–90 new individuals yearly (mean ± SD = 46.8 ± 36.29). Modeled residency using maximum likelihood methods suggested whale sharks spent 49.8 ± S.E. 14.5 [95% CI (32.3–78.6)] days in Donsol each season, with 47.1–60.8 whale sharks at any one time during the season. Twenty individuals were recorded through photo-ID at other sites across the Philippines. The extended residency of whale sharks at Donsol, paired with the presence of sexually mature animals and the economic value of the tourism industry, highlights the importance of Donsol for this endangered species.

This study describes the first record of the whale shark Rhincodon typus association with the cannonball jellyfish Stomolophus meleagris in the Gulf of California, Mexico. Whale sharks were observed swimming and feeding among swarms of jellyfish, suggesting competition and predatory behaviour given the overlap in food preferences between both species. This finding is relevant because of the species‐wide distribution and the importance of these interactions, which should be considered in conservation strategies of R. typus and management of cannonball jellyfish fisheries. [ABSTRACT FROM AUTHOR]

The whale shark Rhincodon typus is an endangered, highly migratory species with a wide, albeit patchy, distribution through tropical oceans. Ten aerial survey flights along the southern Mozambican coast, conducted between 2004–2008, documented a relatively high density of whale sharks along a 200 km stretch of the Inhambane Province, with a pronounced hotspot adjacent to Praia do Tofo. To examine the residency and movement of whale sharks in coastal areas around Praia do Tofo, where they may be more susceptible to gill net entanglement, we tagged 15 juveniles with SPOT5 satellite tags and tracked them for 2–88 days (mean = 27 days) as they dispersed from this area. Sharks travelled between 10 and 2,737 km (mean = 738 km) at a mean horizontal speed of 28 ± 17.1 SD km day−1. While several individuals left shelf waters and travelled across international boundaries, most sharks stayed in Mozambican coastal waters over the tracking period. We tested for whale shark habitat preferences, using sea surface temperature, chlorophyll-a concentration and water depth as variables, by computing 100 random model tracks for each real shark based on their empirical movement characteristics. Whale sharks spent significantly more time in cooler, shallower water with higher chlorophyll-a concentrations than model sharks, suggesting that feeding in productive coastal waters is an important driver of their movements. To investigate what this coastal habitat choice means for their conservation in Mozambique, we mapped gill nets during two dedicated aerial surveys along the Inhambane coast and counted gill nets in 1,323 boat-based surveys near Praia do Tofo. Our results show that, while whale sharks are capable of long-distance oceanic movements, they can spend a disproportionate amount of time in specific areas, such as along the southern Mozambique coast. The increasing use of drifting gill nets in this coastal hotspot for whale sharks is likely to be a threat to regional populations of this iconic species.

The whale shark Rhincodon typus is an endangered, highly migratory species with a wide, albeit patchy, distribution through tropical oceans. Ten aerial survey flights along the southern Mozambican coast, conducted between 2004-2008, documented a relatively high density of whale sharks along a 200 km stretch of the Inhambane Province, with a pronounced hotspot adjacent to Praia do Tofo. To examine the residency and movement of whale sharks in coastal areas around Praia do Tofo, where they may be more susceptible to gill net entanglement, we tagged 15 juveniles with SPOT5 satellite tags and tracked them for 2-88 days (mean D 27 days) as they dispersed from this area. Sharks travelled between 10 and 2,737 km (mean D 738 km) at a mean horizontal speed of 28±17.1 SD km day-1. While several individuals left shelf waters and travelled across international boundaries, most sharks stayed in Mozambican coastal waters over the tracking period. We tested for whale shark habitat preferences, using sea surface temperature, chlorophyll-a concentration and water depth as variables, by computing 100 random model tracks for each real shark based on their empirical movement characteristics. Whale sharks spent significantly more time in cooler, shallower water with higher chlorophyll-a concentrations than model sharks, suggesting that feeding in productive coastal waters is an important driver of their movements. To investigate what this coastal habitat choice means for their conservation in Mozambique, we mapped gill nets during two dedicated aerial surveys along the Inhambane coast and counted gill nets in 1,323 boat-based surveys near Praia do Tofo. Our results show that, while whale sharks are capable of long-distance oceanic movements, they can spend a disproportionate amount of time in specific areas, such as along the southern Mozambique coast. The increasing use of drifting gill nets in this coastal hotspot for whale sharks is likely to be a threat to regional populations of this iconic species. [ABSTRACT FROM AUTHOR]

Whale sharks Rhincodon typus were monitored via acoustic transmitters at the northern end of Western Australia's Ningaloo Marine Park to establish the extent to which the species inhabits the region beyond the whale-shark ecotourism industry season, which usually extends from March to August in each year. Despite the vast majority ( c. 98%) of photographic submissions of R. typus from Ningaloo Reef being between March and August, acoustic detections from the tagged R. typus at Ningaloo were recorded in all months of the year, but do not preclude the occurrence of extended absences. It is concluded that as a species, R. typus occurs year round at Ningaloo, where it generally remains in close proximity to the reef edge, but that some individuals move outside of the detection range of the array for extended periods. [ABSTRACT FROM AUTHOR]

Aim Understanding the spatial and temporal variation in the distribution of migratory species is critical for management and conservation efforts. However, challenges in observing mobile marine species throughout their migratory pathways can impede the identification of critical habitat, linkages between these habitats and threat-mitigation strategies. This study aimed to gain insight into the long-term residency and movement patterns of the whale shark ( Rhincodon typus) and to reveal important habitat in the context of R. typus usage of existing Marine Protected Areas ( MPAs). Location South-eastern Indian Ocean. Methods Satellite telemetry was used to remotely track the long-term movements of 29 R. typus, and to quantify shark usage of the existing MPA network. From the tracking data and environmental predictors, nonlinear models were developed to predict suitable R. typus habitat throughout the south-eastern Indian Ocean. Results This study includes the first documented complete return migrations by R. typus to Ningaloo Marine Park, which was found to be an important area for R. typus all year-round. We found that while existing MPAs along Australia's west coast do afford some protection to R. typus, telemetry-based habitat models revealed large areas of suitable habitat not currently protected, particularly along the Western Australian coast, in the Timor Sea, and in Indonesian and international waters. Main conclusions Animal-borne telemetric devices allowed the gathering of long-term spatial information from the elusive and highly mobile R. typus, revealing the spatial scale of their migration in the south-eastern Indian Ocean. Suitable habitat was predicted to occur inside conservation areas, but our findings indicate that the current MPA network may not sufficiently protect R. typus throughout the year. We suggest that telemetry-based habitat models can be an important tool to inform conservation planning and spatial management efforts for migratory species. [ABSTRACT FROM AUTHOR]

Background: The whale shark (Rhincodon typus) has by far the largest body size of any elasmobranch (shark or ray) species. Therefore, it is also the largest extant species of the paraphyletic assemblage commonly referred to as fishes. As both a phenotypic extreme and a member of the group Chondrichthyes - the sister group to the remaining gnathostomes, which includes all tetrapods and therefore also humans - its genome is of substantial comparative interest. Whale sharks are also listed as an endangered species on the International Union for Conservation of Nature's Red List of threatened species and are of growing popularity as both a target of ecotourism and as a charismatic conservation ambassador for the pelagic ecosystem. A genome map for this species would aid in defining effective conservation units and understanding global population structure. Results: We characterised the nuclear genome of the whale shark using next generation sequencing (454, Illumina) and de novo assembly and annotation methods, based on material collected from the Georgia Aquarium. The data set consisted of 878,654,233 reads, which yielded a draft assembly of 1,213,200 contigs and 997,976 scaffolds. The estimated genome size was 3.44Gb. As expected, the proteome of the whale shark was most closely related to the only other complete genome of a cartilaginous fish, the holocephalan elephant shark. The whale shark contained a novel Toll-like-receptor (TLR) protein with sequence similarity to both the TLR4 and TLR13 proteins of mammals and TLR21 of teleosts. The data are publicly available on GenBank, FigShare, and from the NCBI Short Read Archive under accession number SRP044374. Conclusions: This represents the first shotgun elasmobranch genome and will aid studies of molecular systematics, biogeography, genetic differentiation, and conservation genetics in this and other shark species, as well as providing comparative data for studies of evolutionary biology and immunology across the jawed vertebrate lineages. [ABSTRACT FROM AUTHOR]

The whale shark ( Rhincodon typus) has a high value to tourism, fishing, and pharmaceutical industry, but this species is considered as vulnerable and with potential extinction. The largest aggregation of whale sharks occurs in an upwelling system (Holbox) at northeastern Mexican Caribbean, where we analyzed the trophic role of whale shark. A mass-balanced trophic model was built to: (1) analyze the ecosystem emergent or macroscopic properties; (2) estimate the system recovery time (resilience); (3) assess the fishery effects on different target species; and (4) evaluate the whale shark systemic role in this system. The results showed that the macroscopic properties of the Holbox ecosystem were similar to other upwelling systems with high rates of primary productivity and accumulated biomass in lower trophic levels. Even so, the food web was more like the structure of coral reefs. On the other hand, Holbox system had a lower maturity and development level than coral reefs, suggesting an increased resistance to disturbances. The mixed trophic impacts and short-term dynamic simulation showed that species like snook, sharks, groupers, benthic autotrophs, small benthic epifauna, and phytoplankton had the largest direct and indirect effects. The most significant systemic role of whale sharks is to provide the resilience of the system. [ABSTRACT FROM AUTHOR]

The number of individual whale shark Rhincodon typus sightings registered October 2015–March 2018 in Bahia de La Paz, Mexico, ranged from 73 to 129 animals per season (total 1662), with the majority of them identified as males. Density plot maps showed high correlations in sightings between sample seasons and revealed potential hotspot areas. Our study provides an essential baseline of information for the management of whale shark conservation and the associated touristic activities in the region. [ABSTRACT FROM AUTHOR]