Diving into the world of whale sharks

It has been a very long time since my last blog post. I thought my PhD took all my free time, but it turns out post-PhD paper writing while trying to run a postdoctoral research gig, consumes even more of my life. Nevertheless, I have finally been able to write another blog post! and this time it is very ocean-centric, specifically, I’m delving into the world of whale sharks. These majestic creatures have captivated me for years and have always been at the top of my “things I want to see while diving” list. Unfortunately, I have not had the opportunity to swim with these creatures, however, I do have a friend that has, and it is his story that I am going to tell.

Ben D’Antonio is currently completing his PhD at the University of Western Australia where he is monitoring whale shark migratory behaviour. Ben and I met through volunteering at the Forktree project and got acquainted on a rainy day fixing broken fences and shooing kangaroos out of the property. Ben expressed his dreams to conduct research on whale sharks and had spent time in Indonesia working for conservation international, where he assisted in monitoring and tagging of whale sharks. Now that he is in Western Australia, undertaking his dream research project, shows what you can achieve when you put your mind to it.

His research will be fundamental to protecting whale sharks in Western Australia. These beautiful creatures generate tourism and income for the region as they congregate at Ningaloo reef from March to August each year. Whale sharks have been officially listed as endangered on the IUCN red list and therefore, we have a duty of care to protect these creatures. By looking into migration patterns and more importantly, the drivers of these patterns, Ben’s research will inform key locations for whale sharks that can then be protected. Temperature, prey movement and thermal regulation are all possible reasons as to why whale sharks may migrate and understanding these patterns can help to prevent decline in whale shark populations as our climate changes (Braun et al. 2019). Furthermore, Ben will be looking into the fine scale movements of whale sharks in conjunction with their prey to observe whether any patterns develop. The more we can understand about whale sharks the best chance we have of protecting them.

The biggest threat to whale sharks is us. We, as humans, cause significant damage to whale sharks through our way of life. These are docile, gentle creatures, which is a trait that we take advantage of. In a study that looked at whale shark data from 2006-2018 spanning 338 individuals, 80% of these had some form of injury and 26% were observed to be injured multiple times (Allen et al., 2021). Majority of these injuries were boating accidents, but entanglement in fishing lines has also been observed to cause injury (Speed et al., 2008). The feeding behaviour of whale sharks brings them into shallow waters to thermoregulate (warm up after deep ocean diving), which is normally in proximity to a reef edge or ocean slope that leads to deeper waters containing prey (Copping et al., 2008). Coming into shallower waters makes them vulnerable to boats and humans but despite this, boating accidents do not appear to affect whale shark behaviour as they are known to return multiple times to the same site, even if injured (Araujo et al., 2019). Whale sharks have only been known to alter their behaviour when returning to sites if there has been an extreme weather event such as a tropical storm or cyclone which impacts their food availability (Valsecchi et al. 2021). Thus, if we don’t physical kill whale sharks, our ongoing impact on the climate will result in changed availability of resources for these creatures.

Whale sharks are the teddy bears of the sea that we don’t deserve, unless we radically change our behaviour by preventing fishing in whale shark migration sites, and imposing protection laws for these areas, then we are likely to lose these creatures. Work such as Ben’s will provide new information on whale shark movement, understanding how and why they migrate, and patterns of behaviour in key sites such a Ningaloo, will mean government bodies can be informed of locations to impose restrictions on boat movement. In addition, we can also better predict how whale sharks will respond to future climate change if their migratory behaviour is found to be linked to ocean currents or prey. Our oceans are an interconnected web of species, that all rely on, and impact, one another. Unfortunately, our place in this web is a destructive one, but we can turn this around. We can begin to be a positive force in the oceans’ cycle of life by raising awareness of the damage we are causing and adhering to restricted areas, so let’s start now.

**All photos were taken by Ben D’Antonio while on a field trip and he has given permission for these to be used as part of this blog.

References

Allen HL, Stewart BD, McClean CJ, Hancock J, Rees R. Anthropogenic injury and site fidelity in Maldivian whale sharks (Rhincodon typus). Aquatic Conserv: Mar Freshw Ecosyst. 2021;31:1429–1442. https://doi.org/10. 1002/aqc.3524 

Araujo, G., Agustines, A., Tracey, B. et al. Photo-ID and telemetry highlight a global whale shark hotspot in Palawan, Philippines. Sci Rep 9, 17209 (2019). https://doi.org/10.1038/s41598-019-53718-w

Braun, CD, Gaube, P, Sinclair-Taylor, TH, Skomal, GB, Thorrold, SR (2019) Mesoscale eddies release pelagic sharks from thermal constraints to foraging in the ocean twilight zone. Proceedings of the National Academy of Sciences 116, 17187.

Copping, J.P., Stewart, B.D., McClean, C.J., Hancock, J. and Rees, R., 2018. Does bathymetry drive coastal whale shark (Rhincodon typus) aggregations?. PeerJ6, p.e4904.

Speed, C.W., Meekan, M.G., Rowat, D., Pierce, S.J., Marshall, A.D. and Bradshaw, C.J.A. (2008), Scarring patterns and relative mortality rates of Indian Ocean whale sharks. Journal of Fish Biology, 72: 1488-1503. https://doi.org/10.1111/j.1095-8649.2008.01810.x


Reyes-Mendoza, O., Cárdenas-Palomo, N., Herrera-Silveira, J., Mimila-Herrera, E., Trujillo-Córdova, J., Chiappa-Carrara, X. and Arceo-Carranza, D., 2021. Quantity and quality of prey available for the whale shark (Rhincodon typus, Smith 1828) at the Mexican Caribbean aggregation site. Regional Studies in Marine Science43, p.101696.

S. Valsecchi, C. Lanfredi, A. Azzellino, A. Savini, V. A. Bracchi, F. Marchese, J. Hancock, R. Rees & C. Cánovas Pérez (2021) Analysis of the temporal and spatial variability of whale shark (Rhincodon typus) aggregation in the South Ari Marine Protected Area, Maldives, Indian Ocean, The European Zoological Journal, 88:1, 684-697, DOI: 10.1080/24750263.2021.1922523 

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