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The 4th International Whale Shark Conference
- Conference date: 16-18 May 2016
- Location: Doha, Qatar
- Volume number: 2016
- Published: 15 May 2016
51 - 67 of 67 results
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Caught in the net: A small, resident group of whale sharks feeding among fishing boats
Background Off Mafia Island, Tanzania, whale sharks are seen in a small bay that also boasts one of the country's largest coastal fisheries. We set out to determine the population structure of whale sharks here, examine their feeding behaviour and residency, and investigate the interaction between the sharks and fishers. Approach We conducted 261 boat-based surveys at Mafia Island between Oct 2012 and Dec 2015, recording all whale shark sightings as well as counting the numbers of tourist and fishing boats in the survey area during each trip. We estimated shark size visually and with laser photogrammetry and recorded sex, scars and behaviour of each shark. To examine residency, we deployed 67 acoustic tags on whale sharks and 19 receiver stations within the bay, and analysed recapture probability (both visual- and acoustic-based) with generalised additive mixing models. To investigate feeding plankton biomass and community structure, we collected 20 plankton samples when whale sharks were feeding and 202 background samples for comparison. We interviewed fishers and they recorded their fishing locations using a GPS. Results We identified 129 different whale sharks at Mafia Island, 54% of which were resighted in two or more years. Tagged sharks were acoustically detected throughout the year even though sightings were largely limited to Oct-Mar. Sharks ranged in total length from 2.5–9.7 m, were mostly male (87%), and were usually seen feeding (75%) at or near the surface. Dense patches (25 mg m–3) of large sergestids Lucifer hanseni prompted feeding, while background plankton tows were dominated by small copepods (2.5 mg m–3). Small and medium-sized planktivorous fishes also fed on the same patches of sergestids, often together with whale sharks. These smaller species were the main target of the local fishers. Fishing boats operated in the survey area on 90% of the time, but also made catches further afield. Fishers reported a conflict between whale sharks and their fishing operations on 36% of the time, although sharks were usually released from the nets without injury. A mean of 2.6 tourist boats per day searched the same survey area for whale sharks. Conclusions This small, resident group of whale sharks is routinely exposed to tourists, boat traffic and high fishing pressure. Whale sharks are commonly encircled in fishing nets and released, but scars indicate that they do occasionally get injured during this process. Mortalities are rare, based on interviews with fishers and long-term observers. Whale sharks at Mafia Island are unusually resident and face clear local threats. No defined management measures are currently in place, but we present some potential strategies for mitigating threats to whale sharks here.
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Djibouti – a kindergarten for whale sharks?
Background An aggregation of juvenile whale sharks were first reported off Arta, Djibouti, in 2003 and formally investigated in 2006. Standardised monitoring started in 2009 to establish the demographics of this aggregation and how it relates to the broader Red Sea and Indian Ocean whale shark population. Approach Photo-identification images have been collected from 2003 to present. Satellite relayed archival tags have been deployed to show longer term movements and tissue samples have been collected for DNA. Plankton and environmental information are routinely recorded. For the last two years digital Photo-IDs were collected by volunteers at the local dive operation to enable a longer annual study period to help establish seasonality and sighting trends. Results During 2003–2015, a total of 503 individual sharks were identified by photo-identification from more than 6300 in-water encounters; a maximum of 181 individuals were recorded in a single year. Overall 85% of sharks identified were males and mean body total length ranged from 3.5–4.3 m among years, with no significant difference between sexes. Sharks which were sighted in more than one year had a mean period of inter-annual residency of 4 years (maximum 11 years, n=3). Using data from 2003–2015, mark and recapture models estimated a gross population of 660–777 with 53–78% of individuals being re-sighted in any one year. Satellite tag data showed tagged individuals left the immediate area and travelled into the Red Sea and Northern Indian Ocean; however, 2 of the 3 PAT tagged sharks were seen off Djibouti in subsequent years. Diving depth data showed all sharks made short duration dives to depths greater than 400 m (maximum 832 m) but that all spent at least 45% of the time within 10 m of the surface and an average of 73% of the time shallower than 40 m. Comparison with plankton and environmental data showed that sharks were associated primarily with high plankton concentrations and swimming crab (possibly Charybdis erythrodactyla) spawning events. Conclusions The Arta area off Djibouti is host to a regular and significant aggregation of whale sharks. The average size of the sharks is smaller than those found in other Indian Ocean coastal aggregations suggesting that this may be an intermediate or kindergarten group from which the sharks will leave as they grow to join other juvenile aggregations. Satellite tracking and photo ID support the movement of sharks into Red Sea aggregations.
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Increasing numbers of whale sharks along the Andhra Pradesh coast, India – the conservation and management initiatives taken by EGREE Foundation
Authors: P. Sathiyaselvam, P. Prashanthi, Tarun Kathula, M. Ravi Kumar, Ramesh G. Kalghatgi and S.B.L. MishraBackground The whale shark conservation programme along the East Godavari River Estuarine Ecosystem (EGREE) region, of Andhra Pradesh, east-coast of India, was started in June 2012 under the direction of the Government of India, the United Nations Development Programme, the Global Environment Facility and the Government of Andhra Pradesh Godavari Project. It was started for the conservation and management of globally threatened species protected under the Indian Wildlife (Protection) Act of 1972, and employing cross sectoral mechanisms among various stakeholders, namely enforcement departments (state and central governments), production sectors (industries), fishermen and the public. Approach Questionnaire surveys are conducted to learn the present status of whale sharks along the Andhra Pradesh Coast, and literature surveys are done to understand the past and present whale shark distribution along the east coast of India. Major fish landing centres are monitored to record whale sharks landings, including seasonality, size and sex ratio. Massive awareness programmes and campaigns are conducted to improve the knowledge levels of various stakeholders. A whale shark conservation action plan is being prepared for the Andhra Pradesh coast by cross sectoral mechanisms. Results Fishery experts, researchers and local fishermen opined that until late 2007, the whale shark was a rare visitor to the EGREE region, but the number of sharks has increased in recent years. According to fishermen, whale sharks are seen at a depth of 20–40 m and sometimes come close to shore where they become entangled in shore seine nets. The fishermen revealed that whale sharks are seen mostly solitary or in small groups of 3 to 5 individuals, but sometimes over 200–300 individuals will aggregate in the open sea near the EGREE Region. As per the available literature, the total number of whale sharks killed as bycatch was 20 along the Andhra Pradesh coast between 1889 and 1998 (110 years). But surveys by the EGREE Foundation that between June 2013 and January 2016, 79 individual whale sharks were killed. The whale shark landings happened in all months except during the fishing ban from 16th April to 15th June. In September of 2014, 22 whale sharks were brought to the landing center. Of these 22 sharks, four were alive after being caught in a shore-seine fishing net. Both questionnaire and field surveys revealed that coastal and marine areas of the EGREE region have become a hot spot for whale sharks in recent years. The size of the whale sharks brought to the landing centers ranged between 2.1–6.68 m (mean 3.71±SD 1.04, n=44), and males (58%) outnumbered females. Based on the study, conservation and management measures are being taken by the EGREE Foundation through 1) massive awareness programmes to sensitize the fishermen and local public, 2) education and awareness applied to students and elected representatives of state and central governments, and 3) training of enforcement staff such as the Indian Coast Guard, Marine Police, Fisheries, Forest and Customs and Central Excise. A whale shark conservation action plan is being prepared for the Andhra Pradesh Coast by involving various state and central government departments, production sectors like oil & gas operators, and private port operators, local fishermen and policy makers. Conclusions This study indicated that whale shark numbers have increased and a globally significant aggregation of whale sharks is happening in the coastal and marine areas of EGREE region. Long-term research and monitoring is needed in this region.
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Long-term husbandry and physical observation of the whale sharks in Okinawa Churaumi Aquarium
Authors: Keiichi Sato, Rui Matsumoto, Kiyomi Murakumo and Kiyoshi AsahinaBackground Okinawa Churaumi Aquarium has established a long-term husbandry program for whale sharks since 1980. Currently, three individuals (1 male and 2 female) are housed in the 7,500 m3 capacity main exhibit tank. The male shark was caught by a set-net on March 11, 1995, and it measured a total length (TL) of 460 cm; a subsequent measurement in December 2015 revealed the TL had increased to 865 cm. The corresponding TLs of the female sharks that have been housed in this facility for nine and eight years were 762 cm and 787 cm, respectively. The growth rate, hormonal trends, quantity of food ingested, behaviors, and other physical changes along with maturation of these sharks are presently monitored. Approach The total length of each whale shark was estimated by measuring the length between the snout tip and the first dorsal fin using an equation formulated by us. Periodic measurements of the girth at the posterior margin of the pectoral fin have been recorded since May 2014. For measuring hormonal levels, blood was collected underwater from free-swimming individuals and plasma samples were extracted. The plasma concentration of steroid hormone was measured using time-resolved fluorescent antibody analysis. This data has been collected since May 2008. The quantity of food consumed and the feeding behavior of the whale sharks are recorded each day. Results The TL of the male whale shark increased from 460 cm to 744 cm by March 2005, at an average annual growth rate of 28 cm/year. Since 2005, there has been a decrease in the growth rate, to 12.5 cm/year. The two females have been growing at an annual rate of 33 cm/year (TL = 762 cm) and 37 cm/year (TL = 787 cm). Our data shows that the rate of change of girth appears to be associated with calorie intake. The plasma concentration of steroid hormone of the male shark increased from June 2011 to June 2012 (21.49 ng/ml; TL: 850 cm). This appears to be in synchrony with the rapid elongation of the claspers. Additionally, since April 2012, we have been observing the male shark rotating its entire body laterally crossing both claspers, which is a behavioral indication that the male has reached maturity. Conclusions From our long-term study on captive whale sharks, details on direct observations on the maturity process, growth rate, required food consumption, behavioral patterns, and proportional measurement changes are available. Based on these details, we expect that future attempts for reproduction in captivity would be successful and would allow us to unravel many mysteries of whale shark reproduction.
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Whale shark genetics: Where are we now and where should we be going?
More LessBackground Classic ecological approaches can reveal only glimpses of the behavioral spectrum of a longlived migratory species. Genetic analysis has the potential to inform the migratory behavior and reproductive habits of animals that are difficult or impossible to observe in the wild. Although studied primarily as juveniles at seasonal feeding aggregations, whale sharks are believed to be capable of extensive migrations. The frequency and magnitude of these movements is unknown, as is the degree to which they mediate gene flow between populations. Recent studies have asked whether the sharks observed at different aggregation sites show evidence of genetic structure, or whether they constitute a single breeding population. We published a preliminary study in 2009, based on microsatellite analysis of animals from numerous globally distributed aggregation sites, with a finding of minimal genetic differentiation. Approach Our genetic study is ongoing, and now encompasses hundreds of whale sharks representing all major aggregations worldwide. Other groups have also performed genetic analyses of whale shark population structure, focusing on both regional and global scales. Particularly for studies using microsatellite markers, direct comparisons across laboratories and platforms are not possible. Synthesizing the overall conclusions from aggregate genetic studies, however, provides additional power to understand species behaviors. Results Initial analysis of broadly distributed whale sharks found only low levels of genetic differentiation across geographically distinct populations. While sharks from the Western Atlantic Ocean showed slightly greater differentiation from Pacific/Indian Ocean animals than these populations did from each other, this result was not statistically significant. An expanded data set has now provided stronger analytical resolution between populations, revealing subtle yet statistically significant levels of genetic differentiation of Atlantic sharks. Conclusions Our previous analysis suggested gene flow between whale shark populations at a level sufficient to normalize genetic differentiation. Combined with satellite tracking and other data, these results confirmed that whale sharks can and do migrate between oceans. An expanded study, however, along with data published by other groups, now indicates reduced mixing between Western Atlantic and Indian/Pacific sharks. A significant body of evidence therefore indicates that whale sharks do not have strong population structure, nor do they represent a single panmictic population. Rather they occupy a more biologically realistic intermediate, with varying degrees of isolation by distance and by ecological features. Future genetic characterization should focus on the addition of yet unstudied whale shark populations, on building a robust mitochondrial haplotype dataset with broad applicability, and on technical standardization that could allow comparisons between microsatellite data sets across laboratories and platforms.
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Global shark protection
More LessBackground Sharks have been exploited over decades with very little or no management at all. This had devastating effects on many shark populations around the world. A recent report published by the IUCN Shark Specialist Group in 2014 showed that globally close to 25% of sharks and rays are threatened with extinction. They face more threats today then ever before in history. Primary drivers for this overfishing, as well as much of the bycatch related mortality, is the demand for shark fins used in shark fin soup, the demand for cheap shark meat and other traditional products, as well as the lack of management control along the whole trade chain. Approach In this respect CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) is a good instrument to help in achieving a more sustainable use of sharks and a more species specific management. Another global convention to adress this issue is the Convention on the Conservation of Migratory Species (CMS) and the associated “Sharks MoU.” However, one of the arguments used against further listing of shark species in these conventions is the difficulty of implementation and enforcement. To address this issue, many governments were approached with the offer to do implementation workshops by different NGO's. An important aspect of these workshops is the training of the participants to identify protected species or parts, especially fins, of these animals. Results Whale sharks were among the first two species which got some international protection through their listing on App 2 in CITES in 2002. This has been followed by a rising awareness and additional protection in CMS, different regional fishery regulations or national regulations. This was supported by a whole series of workshops organized by different NGOs, governments and CITES. This has led to a better understanding of the issue and subsequently to additional listings of sharks and manta rays during the last CITES conference in 2013 in Bangkok. Conclusions Since then, aditional workshops have been held and will hopefully lead to better data collection, a more species specific management and ultimately enhanced protection of sharks. They will hopefully help officials in fishery and customs to implement and enforce these new regulations to better manage sharks. First results show positive effects especially in the Middle East and aditional species are proposed to be listed in the above mentioned conventions. This talk informs about international protection of whale sharks and about the recent new CITES and CMS listings of sharks – what they mean and the efforts and global cooperation between NGOs and governments to get there.
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Vertical movement patterns of juvenile whale sharks Rhincodon typus at a seasonal aggregation in Saudi Arabian Red Sea
Background Large marine species have been a focus of scientists and public for their unique role in the ecosystem as well as in conservation. To study the behaviors of large marine species, electrical tagging is a direct and reliable method. Researchers have been utilizing technology advances in biologging tags on multiple spatiotemporal scales. This study provides a detailed insight into the vertical movement of whale sharks in a newly described seasonal aggregation off the coast of Al Lith, Saudi Arabia. Approach In the aggregation season of 2015, two biologging tags were fitted on two juvenile whale sharks and lasted over a period of 22 hours each. Fine-scaled diving behavior was recorded with a sampling rate of 10 Hz and energy consumption was generated from acceleration sensory data. Results Tagged whale sharks exhibited intensive and consistent diving behaviors throughout the day except a prolonged surface swimming in the morning and a brief surfacing around sunset. Deep dives from the two tagged sharks reached 80 meters, which is the depth of this aggregation habitat. In multiple stages of the diel cycle, whale sharks utilized different depths in the water column. Diving speeds also varied among diel stages and between two individuals, most possibly as a strategy of optimizing energy consumption from forage efforts. Combining with previous study on horizontal movement of whale sharks in this aggregation, this study portrays movement behaviors of juvenile whale sharks comprehensively. Conclusions Whale sharks in this aggregation showed a distinct diel vertical movement pattern which also effectively utilizes energy. We hope this study will benefit the management of this hot spot of whale sharks and even larger scale ecosystems, revealing potential excessive human activities (e.g. ecotourism, aquaculture) and global climate issues.
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Photo ID-based assessment of the whale shark (Rhincodon typus) population in Kwatisore, Wondama Bay, West Papua, Indonesia
Authors: Sampari Suruan, Bayu Pranata, Casandra Tania and Mohammad M. KamalBackground The presence of whale sharks (Rhincodon typus) in Wondama Bay has long been known and the species is an icon of this region. In addition to their enormous size, these sharks are not dangerous to or fearful of humans, so there has been growing interest in utilizing this animal for eco-tourism. Within Wondama Bay, whale sharks distribute in several regions, including Kwatisore waters. Since biological information on this species is lacking, the present study aimed to investigate the whale shark population using photo identification, frequency of appearance, sex, and scars on the body. The information obtained from this study is important for species conservation and management. Approach The research was performed in Kwatisore waters of Wondama Bay during 2010–2013, and continued from April to June 2014. Whale shark identification was based on photos taken by divers by plotting three reference points, i.e. the top of the fifth gill slit, the posterior-most point where the pectoral fin meets the body, and the bottom of the fifth gill slit (Brooks et al., 2010). During each encounter, the animals were length measured, sex was identified through the presence or absence of claspers, and the position of scars and wounds were determined on the body. Results The total number of whale sharks encountered in Kwatisore waters were 120 and 19 animals for the period of 2010–2013 and 2014, respectively. Based on ID pictures, the population was composed of 126 sharks consisting of 122 males and 4 females. With regard to 2014 observations, the animals were all males and were immature, as the average body length was 4 m. The greatest number of sharks was observed between 0600–1200 hours, during which time 80 individuals were seen on the surface. It was found that 58% of the population had scars and wounds, of which 34% were on the lips and 25% on the fins. Conclusions Data on IDs and body length of each individual, as well as sex composition, are important information for understanding whale shark population structure, and will benefit the conservation and management of these animals.
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Characteristics of whale sharks (Rhincodon typus) in Teluk Cenderawasih National Park, Indonesia
Background The whale shark (Rhincodon typus) is an iconic species for Teluk Cenderawasih National Park (TCNP), West Papua and Papua. They appear regularly near lift-net fisheries (bagans) year round in some areas, especially near Kwatisore in West Papua, resulting in the development of limited tourism since 2009. The objective of our study was to document the characteristics (i.e., number, size, sex) of whale sharks that occur in TCNP. Approach We used photographs to identify whale sharks from natural patterns and other body markings that periodically appeared near operational bagans in southern Cenderawasih Bay. The photo ID technique was used to identify each individual based on the white body spot pattern. We also made subjective estimates of the relative sizes of each shark and determined whether they were male or female from the presence or absence of claspers. Results We obtained 8,530 photos of sharks from February 2010 through June 2015. From that database we tentatively identified 126 sharks, 83% of them male, 14% female and 3% undetermined. The estimated length of the sharks averaged 4.4 m (± 1.25 m, range = 2 m to 8 m). Around 40% of the individuals had scars, mostly around their mouths and fins. Most (59%) of the sharks were seen in one year, while only 3% were seen over more than one year during the five year study. Some exceptions were one shark that was seen 32 times over four years, and another that was seen 29 times over five years. Conclusions Juvenile male whale sharks appear to be transient and highly mobile in Cenderawasih Bay. Whether adult males or adult females occur here is not known, as they may not be attracted to the fishing bagans or do not otherwise approach the sea surface where they can be observed. Because of the increased tourism for whale sharks and the interactions of whale sharks with the fishing bagans, we recommend continued systematic observations of whale sharks and vigilant surveillance for understanding the dynamics of interactions among tourist activities, fishing operations, and whale sharks.
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Whale shark behavior with swimmers and boats present during tourism activities in the northern Mexican Caribbean
More LessBackground Whale shark watching and swimming are two of the most popular activities for tourists in the northern Mexican Caribbean. Each year since 2002, these activities have had an exponential growth, which could represent a hazard for whale sharks. It is important to monitor the tourism effect on whale shark behavior to take sustainable management measures concerning the use of this natural resource. Approach Whale shark behavior monitoring was conducted from June to September in 2014 and 2015. In order to know the effects of tourism activities and their influence on feeding behaviors and diving paths shown by whale sharks, we conducted surveys to observe whale shark behavior with and without tourism activities (swimmers and boats). Results The monitoring effort in 2014 and 2015 for whale shark surface behavior includes 571 minutes on video, of which 414 minutes include whale shark behavior during tourism activities, and 157 minutes without tourists present. In 2014, 26 whale sharks were observed without tourism activity, and 56% of these sharks showed ram feeding behavior near the surface from the beginning to the end of the observation. 42 whale sharks were observed with tourism; at the beginning of the observation 48% of these sharks presented ram feeding behavior near the surface, but this behavior decreased to 29% to the end of the observation. In 2015, only 7 whale sharks were observed without tourism interactions; 57% had ram feeding behavior from the beginning to the end of the observations. 51 whale sharks were observed with tourism interactions, where 31% of these sharks had ram feeding behavior at the beginning of the survey, but it decreased to 27% by the end of the survey. For 2014, the main behavior was ram feeding behavior. In 2015, the main behavior showed by whale sharks during tourism interactions was diving path behavior (37%). Conclusions Tourism activity might have an effect on whale shark behavior and on surface sightings, indicating a decrease in the surface feeding time in one of the most important feeding aggregations for whale sharks in the northern Mexican Caribbean. Precautionary measures are necessary for adaptive management of tourism activities and the whale sharks in this area.
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Horizontal and vertical movements of the whale shark, Rhincodon typus, in the southern waters of Japan
Background Conservation of whale sharks is making remarkable advances through many studies ongoing in tropical and sub-tropical oceans. However, there have been few studies in the North Pacific Ocean. Some whale shark appearances, as well as by-catch by set-net and purse seining in the southern waters of Japan are reported every year. These waters are important for the conservation ecology of whale sharks because they are the northern limit of the whale shark's distribution and have high productivity influenced by the Kuroshio and Oyashio Currents. However, the habitat and movement of whale sharks around Japan in the North Pacific Ocean are poorly understood. Approach To investigate the habitat and movement of the whale shark, two whale sharks were tagged with PAT-tags (MK-10, Wildlife) and released off the coast of Kouchi, Japan in October 2013 (WS13: 4.2 m in total length) and June 2014 (WS14: 7.2 m). For biological studies and rearing trials, WS13 had been reared for 6 years and 4 months in the Osaka Aquarium of KAIYUKAN, Osaka, and WS14 had been reared for 4 months in the Osaka Aquarium Biological Research Institute of Iburi Center (OBIC) of KAIYUKAN, Kochi, Japan before tagging. The PAT-tags recorded ambient temperature, swimming depth and light level data for 30 and 90 days, respectively, until the detached from the whale shark. After the PAT-tag detachment, the tag floats to the surface and transmits the sampled data via the Argos satellite system. Geolocations of tagged sharks were estimated using light measurement data from the tag and sea surface temperature from the satellite. The horizontal and vertical movements were examined in relation to oceanographic conditions. Results The two sharks moved in the same direction to the east along the Kuroshio Current after being released, despite being released in different seasons. However, WS13 remained in the eddy in the south of the Kuroshio Current, while WS14 crossed the Kuroshio Current to north and remained in the eddy near the Kuroshio-Oyashio transitional area. The total distance WS13 traveled was 1,407 km over 30 days (48.5 km/day), and WS14 traveled 3,022 km over 90 days (29.0 km/day). The mean daily speed while moving along the Kuroshio Current was higher than while remaining in the eddy for both sharks. The primary swimming depth was surface mixed water where the temperature was above 20 °C. The two sharks spent most of their time near the surface above 10 m depth. Diving over the mesopelagic zone (>200 m depth) was rarely observed while the two sharks were traveling along the Kuroshio Current, and wasn't observed while the sharks remained in the eddy. The maximum swimming depth for WS13 was 632 m, and for WS14 was 1560 m, and lowest temperature recorded was 7.1 °C for WS13 and 2.4 °C for WS14 when the sharks were at their maximum depth. Conclusions In southern waters of Japan, horizontal movements of whale sharks are influenced by the Kuroshio Current and the eddy. Their vertical movements are regulated by the thermocline and the threshold temperature was around 20 °C
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Applications for genetic inference to characterise a cryptic life-stage in the whale shark
Background Research efforts on whale sharks have so far been limited to sub-adult males which make-up the vast majority of aggregations around the world. The movements of mature sharks, their reproductive techniques and key habitats remain poorly understood, whilst details of this demographic group are the most important to mitigate current threats. This quandary qualifies the use of indirect analyses such as genetic inference to characterise cryptic life-stages of the species. Approach Tissue samples will be collected from free-swimming whale sharks from locations around the WIO with past biopsy efforts providing additional tissue from every tropical ocean. Photographic identification, approximate visual size and gender information will be recorded for each individual. Microsatellite markers will be extracted from the samples using species-specific primers from previous studies. Additional open access sequences will be obtained via GenBank for appropriate locations. Software packages simulating modes of inheritance such as GERUD will be used to reconstruct parental genotypes. Results This is an outline of potential results of the study. Parental genotype reconstruction can provide information on: 1) Number of parents per litter – maternal genotypes will be reconstructed first as the likelihood of sampling littermates is higher than sampling offspring from different females who happened to mate with the same male. Paternal genotypes can be determined once the maternal genotypes are removed from the progeny sequences. 2) Juvenile recruitment – survival rate of individuals per litter, considering however that juvenile female whale sharks are underrepresented in the majority of sampling areas. Incomplete reconstruction of a parental genotype suggests incomplete offspring sampling. 3) Reproductive mode – i.e. monoor polyandry, demonstrated by single or multiple male genotypes per litter (respectively), which may confirm or refute the single only other demonstration of reproductive mechanism, monandry, in the species. 4) Breeding site fidelity – common and complete parental genotypes of either or both parents within an aggregation or in associated areas (assuming monandry) suggests that whale sharks return to or remain in a common area to pup whereas multiple incomplete genotypes may suggest random dispersal from any given pupping site. Conclusions The reproductive patterns of mature sharks, as inferred by these analyses, will define whale shark movements within their circumglobal range and may highlight important habitats such as breeding or pupping grounds. Resources for protecting the species will be limited and so must target these groups and areas to be most effective at mitigating threats and conserving the species.
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Improving laser-photogrammetry precision for estimates of whale shark total length and applying them to a previously unstudied aggregation of whale sharks at St. Helena Island
Authors: D. Harry Webb, Elizabeth Clingham, Alex Collier, Taylor Stoll and Dr. Alistair DM DoveBackground Laser-photogrammetry is a non-invasive technique used for size estimation in applications where traditional methods to determine length are either impractical or unreliable. Laser photogrammetry provides greater precision for measuring free-swimming whale sharks when compared to previous methods that compare whale sharks to objects of known size such as boat length, diver height, and rope length. These estimates are subject to the effects of water movement and visual distortion from refraction. Laser-photogrammetry uses a known reference distance projected onto a surface using pre-calibrated lasers to standardize measurements and utilizes ratios of pixel-counts to calculate a length estimate. Approach Laser-photogrammetry has been demonstrated as a useful technique for determining body length estimates in free-swimming whale sharks, Rhincodon typus (Rohner et al. 2011), but measures of variance have been lacking because repeat measurements on the same individual animals are rarely obtained. Georgia Aquarium houses 4 juvenile whale sharks that can be unequivocally identified and photographed repeatedly, and therefore provided an opportunity to refine the techniques described by Rohner. We then applied them to an aggregation of whale sharks at St. Helena Island. Results Using a similar laser-photogrammetry apparatus and body proportion equations for determining total length prescribed by Rohner, we observed relatively high variance on repeated measurements made on the same animal, such that confidence intervals for any given individual measurement estimate were unacceptably high. Using measures of central tendency from multiple measurements, rather than relying on single images, provided measurement estimates with acceptable confidence intervals for determining total length. We applied the central tendency technique to characterize lengths in a previously unstudied whale shark aggregation in the southern Atlantic Ocean off of St. Helena Island in 2015 and 2016. We used the mean of 4–27 repeated measurements to determine total length estimates of the individuals photographed in St. Helena during these time periods, instead of relying on single-point photos to determine length estimates for the study. Conclusions At 8.4–10.6 m total length, St. Helena animals are larger than those found in juvenile-dominated coastal aggregation sites like Yucatan, Mexico, but smaller than the large solitary females found in Galapagos. The central tendency approach represents a significant improvement to the photogrammetry method, but it increases workload significantly, so there is still a need to develop non-invasive measurement methods that are accurate, precise, and quick.
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Scarring instance and healing capabilities of whale sharks and possible implications
Authors: Freya C. Womersley, Savinien T. Leblond and David R.L. RowatBackground With increasing levels of tourism and other anthropogenic activities around whale shark aggregations globally there is an increased risk of physical damage to sharks from boat collisions. As such, documenting the occurrence of injuries to sharks can be a useful method of recording the impacts of tourism and other marine based activities as well as the effectiveness of management efforts. The seasonal whale shark aggregation off Djibouti has seen an increase in both physical scarring and tourism and is used here as a case study. Approach Scarring records and photos in the Djibouti whale shark database from 2009 to 2015 were reviewed to establish instance and effects of injury on the viability of whale sharks. To calculate the level of injury, in-water sighting data, which recorded scarring, were sorted into major or minor scar categories after the methods of Speed et al. (2008). Major scars were classified as being potentially life threatening and include fin amputation and lacerations penetrating the sub-dermal layer. The probable origin of the scars was also attributed where possible. To avoid overestimation of population scarring and to make results comparable across aggregations, minor scars (such as abrasions, small bites and nicks) were omitted. To quantify medium-term effects of injury, photographic evidence from returning whale sharks was reviewed to estimate healing rates. Healing rates were obtained using the maximum number of years between observing a fresh injury and a fully healed scar. A fully healed scar was defined as an injury with no non-skin/sub-dermal tissue visible. Results The incidence of major scarring recorded in the Djibouti aggregation varied during the study period from a minimum of 15.6% in 2011 to 27.3% in 2015. Of these, 57.9% were attributable to boat strikes in 2011 compared to 40% in 2015. Lacerations to fins showed the quickest healing rates. Sharks observed with fresh lacerations to the first dorsal fin indicative of propeller strikes showed scar-tissue growth on subsequent re-sighting and fully healed scars within a year. Lacerations to the main body of the sharks showed healing rates of a maximum of two years. Amputations showed a maximum healing time of one year but little capacity for tissue regeneration. However, one case of a partially amputated first dorsal fin showed full re-growth of the fin after five years, an instance that is exceptional and has not been recorded before. Conclusions When reviewing scar photos it is clear that whale sharks have the ability to tolerate major injuries through their extraordinary regenerative capabilities. This suggests that whale sharks can recover from boat strikes; however, sharks that did not survive strikes will not be re-recorded and would show as a loss from the dataset. Similarly, the long-term hindrances to normal behavior that are caused by major injuries remain largely unknown. The study reinforces the need for a series of regulations including speed limits to be implemented and enforced within the study site, Arta Marine Protected Area, Djibouti. This approach of recording scars can be applied to other shark populations to improve understanding of shark healing capabilities and the species as a whole.
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Stable isotope analysis for the whale shark in the waters off Taiwan
Authors: Chi-Ju Yu, Shoou-Jeng Joung, Kwang-Ming Liu, Hua-Hsun Hsu and Chia-Yen LinBackground The whale shark, Rhincodon typus, was utilized extensively in Taiwan before 1996. A quota management measure was put in place in 2002, and the whale shark fishery was completely banned in 2008. Biological studies including age and growth, and migration/ movement have been conducted. However, the feeding ecology of whale sharks in different life history stages and sexes in Taiwan waters (Northwest Pacific Ocean) is still unknown. Approach The stable isotope technique was used to analyze the tissue of whale sharks to understanding their feeding ecology. The ´13C value can be used to indicate the foraging habitat of fish, and the ´15N value can be used to estimate the relative position of the consumer in the ecosystem. The specimens (tissue) were taken from individuals entangled in set nets during the period 2008 – 2013 in Taiwan. Results In total, 66 tissue samples from 42 males and 24 females, ranging from 2.84 to 11.90 m TL (total length) were used in stable isotope analysis. Among these specimens 50 and 16 were from the eastern and western waters off Taiwan, respectively. The value of ´13C was from –13.68 to –18.42%, and the value of ´15N was from 5.17 to 13.01%. There was a positive relationship between ´13C and ´15N, and both ´13C and ´15N increased with body size. No gender or geographic difference was found in this study, but the range of stable isotope values of whale shark tissue was wider in eastern Taiwan waters. Conclusions In this study, ontogenetic changes in the diet of whale sharks were found. More specimens are needed to examine the differences in stable isotope values among different genders, seasons, and regions. The results derived from this study can provide useful information on the husbandry of whale sharks, which can help ecotourism operators become more knowledgeable about the ecology of whale sharks. In addition, the results can also be used as an important reference for ecosystem-based management in the future. Future work should focus on discussion on the habitat partition, utilization, and adaption in various marine environments for whale sharks.
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Intraspecific variability in diet and implied foraging ranges of whale sharks at Ningaloo Reef, Western Australia
Background The whale shark (Rhincodon typus Smith 1828) is the largest of the filter-feeding sharks and inhabits tropical and sub-tropical oceans worldwide. Evidence from anecdotal observations of feeding events and stomach content analysis have identified a wide range of planktonic and nektonic organisms including copepods, krill and small fish as whale shark prey. However, recent studies based on biochemical analysis (e.g. signature fatty acids (FA)) indicated that whale sharks in the western Indian Ocean had a wider foraging range than previous studies suggested, with important contributions from meso- and bathypelagic sources. However, it remains unknown if these results characterize the diet of whale sharks over the wider Indian Ocean. Here, we investigate the feeding ecology of whale sharks in the eastern Indian Ocean at Ningaloo Reef, Western Australia, by identifying differences in whale shark diet according to time of collection, sex and size-class and by examining likely food web linkages. Approach To examine whale shark feeding ecology we used signature FA analysis of both whale shark subdermal tissue and an extensive set of potential prey collected at Ningaloo Reef (Western Australia) in 2013 and 2014. Compared to other methods such as stomach content analysis, signature FA analysis provides both longer-term (up to months) dietary information and an assessment of spatial and temporal changes in the diet of predators. This is possible because some FA in animal tissues (e.g. long-chain (≥C20) polyunsaturated FA, LC-PUFA) can be used as biomarkers as they pass relatively unchanged from the low trophic levels where they are biosynthesized up the food chain. Results Whale shark sub-dermal tissue was low in lipid content (4 mg g–1 dry mass) which was dominated by phospholipids (72% of total lipid) with an energy density of 18.66 kJ g–1 dry mass. A significant intraspecific variability in whale shark FA profiles was observed resulting in four distinct groups of sharks in 2013 and five in 2014. As this variability was not related to sex or size-class, we suggest that it may be attributed to differences in the feeding habitats and thus different prey consumed by these groups of whale sharks. Variation in dietary patterns was also observed between years likely due to changes in the primary and secondary producers. Overall, examination of food web interactions showed that fatty acid profiles of whale sharks and their presumed collected prey were significantly different, suggesting that sharks fed over a wider range of habitats, including deeper waters, than we were able to access. Conclusions A significant component of whale shark diet may originate from benthic and deeper water habitats. High intraspecific variation in diet indicates that whale sharks are likely to forage over a range of distances and depths due to the challenge of inhabiting the patchy prey habitats of tropical and open ocean waters. Future studies should seek to combine signature FA analysis with other techniques such as stable isotopes, genetic and longterm tagging data to help better elucidate the feeding ecology of this iconic species.
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Human dimensions of whale shark provisioning in Oslob, Philippines
Authors: Jackie A. Ziegler, Joshua N. Silberg, Alessandro Ponzo and Philip DeardenBackground Whale shark tourism can provide an incentive to protect whale sharks and their habitats by making them worth more alive than dead. However, the sustainability of these tourism activities is critical to the long-term success of this approach. Whale shark tourism in Oslob is one of only two places in the world where tour operators feed whale sharks to facilitate tourist interactions. To date, no comprehensive studies have assessed tourists' attitudes towards whale shark provisioning. This study assesses tourists' support for whale shark provisioning, as well as their satisfaction with the tour experience in Oslob. Approach TripAdvisor comments of the Oslob whale shark watching experience (n=216) were thematically coded and analysed in NViVO 10. Tourist surveys were collected during the 2014 whale shark watching season in Oslob (n=761) in order to measure attitudes towards interactions with whale sharks. Survey results were coded and analysed in SPSS Version 21. Results TripAdvisor analysis identified four main issues with the experience in Oslob: crowding, provisioning, impacts on sharks, and pricing. Survey results suggest that foreign tourists were significantly more likely to feel crowded compared to national tourists, both in terms of number of other snorkelers (37% vs. 19%; χ2(1, N=629)=23.475, p=0.000, Cramer's V = 0.193) and number of boats (50% vs. 28%; χ2(1, N=623)=30.919, p=0.000, Cramer's V = 0.223), despite the fact that both groups reported encountering the same number of people. Both the survey and TripAdvisor analyses found no significant difference in overall satisfaction with the tour between foreign and national tourists. However, the TripAdvisor analysis did identify a foreign tourist segment termed ‘guilty pleasure’, which exhibited negative feelings towards the ethics of whale shark feeding and an unwillingness to return to Oslob, but still recommended the tour to others. These findings were reflected in the survey results. Foreign tourists were significantly less likely to be willing to participate in whale shark tourism in Oslob again (62%) compared to national tourists (90%; χ2(1, N=632)=67.686, p=0.000, Cramer's V = 0.327), but the vast majority of both foreign (93%) and national (99%) tourists would still recommend the tour (χ2(1, N=632)=18.153, p=0.000, Cramer's V = 0.169). Foreign tourists were also significantly less likely to support the feeding of whale sharks than national tourists (35% vs. 65%; χ2(2, N=635)=55.209, p=0.000, Cramer's V = 0.295), with a further 35% and 22% neutral on the topic, respectively. Although the majority of both groups felt the price of the tour was appropriate, foreign tourists were willing to pay significantly more for the whale shark experience than national tourists (US$63 vs. US$33; t=–6.020, p=0.000, rpb=0.245). Foreign tourists were willing to pay the most for an experience where sharks were not fed, but there was 100% chance of seeing a shark (US$64), followed by sharks fed with 100% chance of seeing sharks (US$43). National tourists on the other hand were willing to pay US$17 for an experience where there was 100% chance of seeing a shark regardless of whether the sharks were fed. Conclusions Few participants perceived the feeding of whale sharks as a negative activity, although foreign tourists were less supportive than national tourists. Most foreign tourists would recommend the tour to others despite their stated intention to not return and misgivings regarding the ethics of provisioning or potential impacts on whale shark health. More in-depth interpretation is necessary to inform tourists of the conservation status and threats facing whale sharks, as well as the potential impacts of tourism activities, both positive and negative. Furthermore, the number of boats and swimmers should be controlled in the whale shark viewing area to address crowding issues.
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