The 4th International Whale Shark Conference

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.

Background 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.

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.