Regional movements of satellite‐tagged whale sharks Rhincodon typus in the Gulf of Aden

To gain insight into whale shark (Rhincodon typus) movement patterns in the Western Indian Ocean, we deployed eight pop‐up satellite tags at an aggregation site in the Arta Bay region of the Gulf of Tadjoura, Djibouti in the winter months of 2012, 2016, and 2017. Tags revealed movements ranging from local‐scale around the Djibouti aggregation site, regional movements along the coastline of Somaliland, movements north into the Red Sea, and a large‐scale (>1,000 km) movement to the east coast of Somalia, outside of the Gulf of Aden. Vertical movement data revealed high occupation of the top ten meters of the water column, diel vertical movement patterns, and deep diving behavior. Long‐distance movements recorded both here and in previous studies suggest that connectivity between the whale sharks tagged at the Djibouti aggregation and other documented aggregations in the region are likely within annual timeframes. In addition, wide‐ranging movements through multiple nations, as well as the high use of surface waters recorded, likely exposes whale sharks in this region to several anthropogenic threats, including targeted and bycatch fisheries and ship‐strikes. Area‐based management approaches focusing on seasonal hotspots offer a way forward in the conservation of whale sharks in the Western Indian Ocean.     

Horizontal Movements,Migration Patterns,and Population Structure of Whale Sharks in the Gulf of Mexico and Northwestern Caribbean Sea

Whale sharks, Rhincodon typus, aggregate by the hundreds in a summer feeding area off the northeastern Yucatan Peninsula, Mexico, where the Gulf of Mexico meets the Caribbean Sea. The aggregation remains in the nutrient-rich waters off Isla Holbox, Isla Contoy and Isla Mujeres, Quintana Roo for several months in the summer and then dissipates between August and October. Little has been known about where these sharks come from or migrate to after they disperse. From 2003–2012, we used conventional visual tags, photo-identification, and satellite tags to characterize the basic population structure and large-scale horizontal movements of whale sharks that come to this feeding area off Mexico. The aggregation comprised sharks ranging 2.5–10.0 m in total length and included juveniles, subadults, and adults of both sexes, with a male-biased sex ratio (72%). Individual sharks remained in the area for an estimated mean duration of 24–33 days with maximum residency up to about 6 months as determined by photo-identification. After leaving the feeding area the sharks showed horizontal movements in multiple directions throughout the Gulf of Mexico basin, the northwestern Caribbean Sea, and the Straits of Florida. Returns of individual sharks to the Quintana Roo feeding area in subsequent years were common, with some animals returning for six consecutive years. One female shark with an estimated total length of 7.5 m moved at least 7,213 km in 150 days, traveling through the northern Caribbean Sea and across the equator to the South Atlantic Ocean where her satellite tag popped up near the Mid-Atlantic Ridge. We hypothesize this journey to the open waters of the Mid-Atlantic was for reproductive purposes but alternative explanations are considered. The broad movements of whale sharks across multiple political boundaries corroborates genetics data supporting gene flow between geographically distinct areas and underscores the need for management and conservation strategies for this species on a global scale.     

Whale Shark (Rhincodon typus) Seasonal Presence,Residence Time and Habitat Use at Darwin Island,Galapagos Marine Reserve

The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin''s Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island''s vicinity. Sharks showed a preference for intermediate depths (20–30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24–25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species.     

Vertical Movements and Patterns in Diving Behavior of Whale Sharks as Revealed by Pop-Up Satellite Tags in the Eastern Gulf of Mexico

The whale shark (Rhincodon typus) is a wide-ranging, filter-feeding species typically observed at or near the surface. This shark’s sub-surface habits and behaviors have only begun to be revealed in recent years through the use of archival and satellite tagging technology. We attached pop-up satellite archival transmitting tags to 35 whale sharks in the southeastern Gulf of Mexico off the Yucatan Peninsula from 2003–2012 and three tags to whale sharks in the northeastern Gulf off Florida in 2010, to examine these sharks’ long-term movement patterns and gain insight into the underlying factors influencing their vertical habitat selection. Archived data were received from 31 tags deployed on sharks of both sexes with total lengths of 5.5–9 m. Nine of these tags were physically recovered facilitating a detailed long-term view into the sharks’ vertical movements. Whale sharks feeding inshore on fish eggs off the northeast Yucatan Peninsula demonstrated reverse diel vertical migration, with extended periods of surface swimming beginning at sunrise followed by an abrupt change in the mid-afternoon to regular vertical oscillations, a pattern that continued overnight. When in oceanic waters, sharks spent about 95% of their time within epipelagic depths (<200 m) but regularly undertook very deep (“extreme”) dives (>500 m) that largely occurred during daytime or twilight hours (max. depth recorded 1,928 m), had V-shaped depth-time profiles, and comprised more rapid descents (0.68 m sec^-1) than ascents (0.50 m sec^-1). Nearly half of these extreme dives had descent profiles with brief but conspicuous changes in vertical direction at a mean depth of 475 m. We hypothesize these stutter steps represent foraging events within the deep scattering layer, however, the extreme dives may have additional functions. Overall, our results demonstrate complex and dynamic patterns of habitat utilization for R. typus that appear to be in response to changing biotic and abiotic conditions influencing the distribution and abundance of their prey.     

Acoustic telemetry reveals cryptic residency of whale sharks

Although whale sharks (Rhincodon typus) have been documented to move thousands of kilometres, they are most frequently observed at a few predictable seasonal aggregation sites. The absence of sharks at the surface during visual surveys has led to the assumption that sharks disperse to places unknown during the long ‘off-seasons’ at most of these locations. Here we compare 2 years of R. typus visual sighting records from Mafia Island in Tanzania to concurrent acoustic telemetry of tagged individuals. Sightings revealed a clear seasonal pattern with a peak between October and February and no sharks observed at other times. By contrast, acoustic telemetry demonstrated year-round residency of R. typus. The sharks use a different habitat in the off-season, swimming deeper and further away from shore, presumably in response to prey distributions. This behavioural change reduces the sharks'' visibility, giving the false impression that they have left the area. We demonstrate, for the first time to our knowledge, year-round residency of unprovisioned, individual R. typus at an aggregation site, and highlight the importance of using multiple techniques to study the movement ecology of marine megafauna.     

Reef-Fidelity and Migration of Tiger Sharks,Galeocerdo cuvier,across the Coral Sea

Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km³. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.     

Complex Movements,Philopatry and Expanded Depth Range of a Severely Threatened Pelagic Shark,the Oceanic Whitetip (Carcharhinus longimanus) in the Western North Atlantic

Oceanic whitetip sharks (Carcharhinus longimanus) have recently been targeted for conservation in the western North Atlantic following severe declines in abundance. Pop-up satellite archival tags were applied to 11 mature oceanic whitetips (10 females, 1 male) near Cat Island in the central Bahamas 1–8 May 2011 to provide information about the horizontal and vertical movements of this species. Another large female was opportunistically tagged in the U.S. Exclusive Economic Zone (EEZ). Data from 1,563 total tracking days and 1,142,598 combined depth and temperature readings were obtained. Sharks tagged at Cat Island stayed within 500 km of the tagging site for ∼30 days before dispersing across 16,422 km² of the western North Atlantic. Maximum individual displacement from the tagging site ranged from 290–1940 km after times at liberty from 30–245 days, with individuals moving to several different destinations (the northern Lesser Antilles, the northern Bahamas, and north of the Windward Passage). Many sharks returned to The Bahamas after ∼150 days. Estimated residency times within The Bahamas EEZ, where longlining and commercial trade of sharks is illegal, were generally high (mean = 68.2% of time). Sharks spent 99.7% of their time shallower than 200 m and did not exhibit differences in day and night mean depths. There was a positive correlation between daily sea surface temperature and mean depth occupied, suggesting possible behavioral thermoregulation. All individuals made short duration (mean = 13.06 minutes) dives into the mesopelagic zone (down to 1082 m and 7.75°C), which occurred significantly more often at night. Ascent rates during these dives were significantly slower than descent rates, suggesting that these dives are for foraging. The sharks tracked appear to be most vulnerable to pelagic fishing gear deployed from 0–125 m depths, which they may encounter from June to October after leaving the protected waters of The Bahamas EEZ.     

Population structure of a whale shark Rhincodon typus aggregation in the Red Sea

The presence of whale sharks Rhincodon typus were recorded around Shib Habil, a small, coastal reef off the Red Sea coast of Saudi Arabia, from 2010 to 2015. A total of 267 suitable photographs resulting in the identification of 136 individuals, were documented from 305 encounters. Sharks were divided evenly between the sexes with no evidence of temporal or spatial segregation. All individuals were immature based on size estimates and, for males, juvenile clasper morphology. Scars were reported for 57% of R. typus with 15% showing evidence of propeller trauma. Estimates of population size and patterns of residency were calculated by modelling the lagged identification rate. Multiple models were run simultaneously and compared using the Akaike information criterion. An open population model was found to best represent the data and estimates a daily abundance between 15 and 34 R. typus during the aggregation season, with local residence times ranging from 4 to 44 days. Residence times away from Shib Habil range from 15 to 156 days with a permanent emigration–death rate between 0·07 and 0·58 individuals year^?1. These results are broadly similar to those from other aggregations of R. typus, although the observed sexual parity and integration found at this site is unique for the species and needs further study.     

Feeding habits of the whale shark (<Emphasis Type="Italic">Rhincodon typus</Emphasis>) inferred by fatty acid profiles in the northern Mexican Caribbean

Whale shark (Rhincodon typus, Smith, 1828) is an endangered species with anthropogenic pressures due to increasing demand of encounter tourism activities. Research efforts to identify management and conservation strategies for this species are needed. The Northern Mexican Caribbean is one of the most important feeding aggregation sites of whale sharks worldwide. In this study, Mexican Caribbean whale shark feeding habits are assessed by means of fatty acid (FA) signature analysis, a biochemical non-destructive technique widely applied in trophic ecology studies. Sub-dermal tissue biopsies of 68 whale sharks and samples of their potential prey (zooplankton) were collected during 2010 and 2011 in two areas with high R. typus abundance. Zooplankton samples (n?=?17) were divided in two categories: mixed zooplankton (several groups of zooplankton) and fish eggs (> 95% of sample components were fish eggs). FA profiles of whale shark tissue sampled between years showed significant variability; while there was no intraspecific differences in FA signature related to sex, size and location. FA profiles of whale sharks and their potential prey were dominated by saturated fatty acids (SFA). R. typus FA signature was significantly different from that of mixed zooplankton; on the other hand, whale shark and fish egg FA profiles formed groups with overlapping values and registered high levels of oleic acid. PUFA average ω3/ ω6 ratio on whale shark FA profiles for both years was below 1. Arachidonic acid (ARA) percentage was higher in whale shark biopsies (13.2% in 2010, 6.8% in 2011) compared to values observed in fish eggs (2.0%) and mixed zooplankton (1.4%). Similarity between FA profiles of whale sharks and fish eggs, low levels of bacterial FA found in R. typus biopsies, as well as whale shark feeding behavior observations in the study area, suggest that R. typus is feeding mainly on surface zooplankton in Mexican Caribbean; however, elevated ARA percentages in whale shark samples may indicate that this species has complementary feeding sources, such as demersal zooplankton, which has been reported in other aggregation sites. Results obtained contribute to the knowledge of the whale shark trophic ecology in the area, but are inconclusive. Further studies are recommended to evaluate whale shark FA profiles from different tissues (muscle or blood); also, broader information is needed about zooplankton FA signature in the study area.     

Movement and behaviour patterns of the critically endangered common skate Dipturus batis revealed by electronic tagging

Understanding animal distributions and habitat utilisation is vital for the management of populations, especially those of endangered species. However, this information is not available for the majority of marine species and is difficult to obtain for those with low population densities. The common skate, Dipturus batis, was once abundant and widespread in the North-East Atlantic but is now thought to be locally extinct in the Irish Sea and in the central and southern North Sea, and is listed as Critically Endangered on the IUCN Red List. The constraints of skate body morphology on locomotory mode assume low levels of activity with long periods spent resting on the seabed, therefore predicting a high degree of site fidelity. To investigate this hypothesis we tagged 8 common skate (two male and six female, mass range: 10.9–63.5 kg) with depth and temperature-logging data storage tags off the west coast of Scotland in May 2008. All 6 tags attached to females were recovered after 1–9 months at liberty. All 6 individuals exhibited pronounced site fidelity to highly localised areas. Within these local areas however, time-depth profiles were dominated by periods of high activity, with vertical movements of > 100 m being conducted on a regular, sometimes daily, basis. Intra-individual plasticity was observed in vertical activity patterns with individuals switching between low and high activity patterns. Smaller skate were generally less active and occupied deeper depths. Limited short-term horizontal movements in preferred habitats supporting apparently high foraging activity highlights the need for spatial management of ‘refugial’ populations of this once widespread fish, that appears now largely extirpated from European waters.     

Biomarkers of Whale Shark Health: A Metabolomic Approach

In a search for biomarkers of health in whale sharks and as exploration of metabolomics as a modern tool for understanding animal physiology, the metabolite composition of serum in six whale sharks (Rhincodon typus) from an aquarium collection was explored using ¹H nuclear magnetic resonance (NMR) spectroscopy and direct analysis in real time (DART) mass spectrometry (MS). Principal components analysis (PCA) of spectral data showed that individual animals could be resolved based on the metabolite composition of their serum and that two unhealthy individuals could be discriminated from the remaining healthy animals. The major difference between healthy and unhealthy individuals was the concentration of homarine, here reported for the first time in an elasmobranch, which was present at substantially lower concentrations in unhealthy whale sharks, suggesting that this metabolite may be a useful biomarker of health status in this species. The function(s) of homarine in sharks remain uncertain but it likely plays a significant role as an osmolyte. The presence of trimethylamine oxide (TMAO), another well-known protective osmolyte of elasmobranchs, at 0.1–0.3 mol L⁻¹ was also confirmed using both NMR and MS. Twenty-three additional potential biomarkers were identified based on significant differences in the frequency of their occurrence between samples from healthy and unhealthy animals, as detected by DART MS. Overall, NMR and MS provided complementary data that showed that metabolomics is a useful approach for biomarker prospecting in poorly studied species like elasmobranchs.     

Observations on Abundance of Bluntnose Sixgill Sharks,Hexanchus griseus,in an Urban Waterway in Puget Sound, 2003-2005

The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed but poorly understood large, apex predator. Anecdotal reports of diver-shark encounters in the late 1990’s and early 2000’s in the Pacific Northwest stimulated interest in the normally deep-dwelling shark and its presence in the shallow waters of Puget Sound. Analysis of underwater video documenting sharks at the Seattle Aquarium’s sixgill research site in Elliott Bay and mark-resight techniques were used to answer research questions about abundance and seasonality. Seasonal changes in relative abundance in Puget Sound from 2003–2005 are reported here. At the Seattle Aquarium study site, 45 sixgills were tagged with modified Floy visual marker tags, along with an estimated 197 observations of untagged sharks plus 31 returning tagged sharks, for a total of 273 sixgill observations recorded. A mark-resight statistical model based on analysis of underwater video estimated a range of abundance from a high of 98 sharks seen in July of 2004 to a low of 32 sharks seen in March of 2004. Both analyses found sixgills significantly more abundant in the summer months at the Seattle Aquarium’s research station.     

Telemetry and Satellite Tracking of Whale Sharks, Rhincodon Typus, in the Sea of Cortez, Mexico, and the North Pacific Ocean

We used satellite-linked radio telemetry to document the geographic and vertical movements and thermal habitats of whale sharks in the Sea of Cortez and as they migrated into the north Pacific Ocean. Of 17 sharks tagged between 1994 and 1996, six dispersed widely in the Sea of Cortez during 12–39 days of tracking. Four others left the Sea of Cortez and ranged extensively in the north Pacific Ocean. Indeed, one whale shark migrated to the western north Pacific Ocean, covering over 13000km in 37 months of tracking. The sharks generally occupied areas where sea surface water temperatures were between 28 and 32°C, though several ranged to depths of 240m or deeper where water temperature reached 10°C or colder. Whale sharks may segregate by size and sex, and their movement patterns appear to be related to oceanographic features, such as sea mounts and boundary currents, where primary productivity may be enhanced. These results have important implications for the global conservation of the world's largest yet least known fish. We think that satellite telemetry is a exceptionally promising tool for learning more about the ecology of whale sharks, especially when combined with conventional methods of telemetry and molecular biology.authorship arranged alphabetically     

Aggregation behavior of the grey reef shark, Carcharhinus amblyrhynchos, at Johnston Atoll, Central Pacific Ocean

Free-ranging female grey reef sharks, Carcharhinus amblyrhynchos, were observed forming daily aggregations offshore Sand Island, Johnston Atoll between March and late May from 1992 to 1995. Daily water temperatures were recorded at the aggregation area from 1993 to 1995. The annual aggregation cycle did not coincide with maximum or minimum annual water temperatures. During the 1994 aggregation, temperatures were recorded at least every hour at 7 sites in the Atoll. The sharks aggregated most frequently and in highest numbers at the largest and shallowest site, which also contained the fewest underwater structures. The water temperature at this site was 1–2 °C warmer than at neighboring sites and at a reef channel between the lagoon and the open ocean. The pattern of movement of sharks to and from the aggregation area was correlated with daily fluctuations of water temperature (r=0.38; p < 0.001), tide (r=0.30; p < 0.001) and light level (r=0.21; p < 0.001) after adjustment for autocorrelated errors. The daily maximum number of aggregating sharks coincided with the daily maximum water temperature. However, the number of aggregating sharks did not necessarily increase during days of higher water temperature. During the 1994 aggregation period, four sharks were fed ultrasonic telemetry tags, and telemetry stations were deployed at three sites within the aggregation area. Individual sharks were tracked returning to the aggregation area for durations of one to five days. The end of detection of tagged sharks is thought to be due to the regurgitation of the indigestible tags, rather than the sharks permanent departure from the aggregating area. Sharks aggregated only during the day; none of the tagged sharks were recorded and no sharks were ever seen at the aggregation area during night time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Unexpected Positive Buoyancy in Deep Sea Sharks,Hexanchus griseus,and a Echinorhinus cookei

We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200–300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200–300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.     

Intraspecific variation in vertical habitat use by tiger sharks (Galeocerdo cuvier) in the western North Atlantic

Tiger sharks (Galeocerdo cuvier) are a wide ranging, potentially keystone predator species that display a variety of horizontal movement patterns, making use of coastal and pelagic waters. Far less, however, is known about their vertical movements and use of the water column. We used pop‐up satellite archival tags with two data sampling rates (high rate and standard rate tags) to investigate the vertical habitat use and diving behavior of tiger sharks tagged on the Puerto Rico–Virgin Islands platform and off Bermuda between 2008 and 2009. Useable data were received from nine of 14 sharks tagged, tracked over a total of 529 days. Sharks spent the majority of their time making yo‐yo dives within the upper 50 m of the water column and considerable time within the upper 5 m of the water column. As a result, sharks typically occupied a narrow daily temperature range (~2°C). Dives to greater than 200 m were common, and all sharks made dives to at least 250 m, with one shark reaching a depth of 828 m. Despite some similarities among individuals, a great deal of intraspecific variability in vertical habit use was observed. Four distinct depth distributions that were not related to tagging location, horizontal movements, sex, or size were detected. In addition, similar depth distributions did not necessitate similar dive patterns among sharks. Recognition of intraspecific variability in habitat use of top predators can be crucial for effective management of these species and for understanding their influence on ecosystem dynamics.     

Segregation and foraging ecology of whale sharks, Rhincodon typus, in the southwestern Gulf of California

Sharks segregate by sex and size, but few studies have attempted to explain such behaviors. To address this, we examined aggregations and the foraging ecology of whale sharks in Bahía de La Paz (BLP) with aerial and ship surveys and direct observation. Zooplankton abundance and composition, and hydrographic conditions were analyzed in relation to whale shark occurrence to explore underlying factors causing segregations. We observed large aggregations of juveniles (<9 m total length, TL) inshore, comprised by 60 % male individuals, and small aggregations of adults (>9 m TL) offshore, composed of 84 % females. Juvenile sharks were associated to turbid shallow waters in BLP, where they performed stationary and dynamic suction feeding on dense copepod swarms. Adults occurred in oceanic waters and fed by ram-filtering on diffuse patches of euphausiids, with no association to oceanographic conditions. Such segregation may be advantageous to juvenile R. typus utilizing shallow coastal waters to find abundant preferred prey needed for their fast growth rates. Our studies suggest that the main driving forces of whale shark segregation by sex and size in BLP may be diet preference for juveniles and habitat preference for adult sharks.     

Do they stay or do they go? Acoustic monitoring of whale sharks at Ningaloo Marine Park,Western Australia

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.     

Whale Sharks,Rhincodon typus,Aggregate around Offshore Platforms in Qatari Waters of the Arabian Gulf to Feed on Fish Spawn

Whale sharks, Rhincodon typus, are known to aggregate to feed in a small number of locations in tropical and subtropical waters. Here we document a newly discovered major aggregation site for whale sharks within the Al Shaheen oil field, 90 km off the coast of Qatar in the Arabian Gulf. Whale sharks were observed between April and September, with peak numbers observed between May and August. Density estimates of up to 100 sharks within an area of 1 km² were recorded. Sharks ranged between four and eight metres’ estimated total length (mean 6.92±1.53 m). Most animals observed were actively feeding on surface zooplankton, consisting primarily of mackerel tuna, Euthynnus affinis, eggs.     

Multi-Year Impacts of Ecotourism on Whale Shark (Rhincodon typus) Visitation at Ningaloo Reef,Western Australia

In-water viewing of sharks by tourists has become a popular and lucrative industry. There is some concern that interactions with tourists with ecotourism operations might harm sharks through disruption of behaviours. Here, we analysed five years of whale shark (Rhincodon typus) encounter data by an ecotourism industry at Ningaloo Reef, Western Australia, to assess the impact of ecotourism interactions on shark visitation, within the context of the biological and physical oceanography of the region. Our data base consisted of 2823 encounter records for 951 individual whale sharks collected by ecotourism operators between 2007 and 2011. We found that total encounters per whale shark and encounters per boat trip increased through time. On average, whale sharks re-encountered in subsequent years were encountered earlier, stayed longer and tended to be encountered more often within a season than sharks that were only encountered in a single year. Sequential comparisons between years did not show any patterns consistent with disturbance and the rate of departure of whale sharks from the aggregation was negatively correlated to the number of operator trips. Overall, our analysis of this multi-year data base found no evidence that interactions with tourists affected the likelihood of whale shark re-encounters and that instead, physical and biological environmental factors had a far greater influence on whale shark visitation rates. Our approach provides a template for assessing the effects of ecotourism interactions and environmental factors on the visitation patterns of marine megafauna over multiple years.