Hey urban nomads, in our previous post, we spent some time talking about the benefits of whale shark tourism but as you can imagine, the bulk of this post will be on the issues that this form of tourism pose on the environment.
Ingestion of plastic
To find out how much plastic whale sharks ingest in an environment that has been heavily visited by humans, an experiment was done whereby researchers dragged a fine mesh net through the water, simulating how whale sharks swim with their mouths open. It was found that during the wet season, the sharks can ingest up to 63 pieces of plastic per hour (Thomsen , 2019).
Aside from experiments above which aim to estimate how much plastic sharks ingest, there are several photo evidence which can prove the point as well. Exposure and ingestion of plastic can disturb the regular function of the endocrine system, which affects the growth and reproduction of sharks (Thomsen , 2019). Given that sharks are endangered species, it is definitely not favourable if such human-induced activities affect the population of the sharks.
Propeller cuts & provisioning
Whale shark sustained injuries from propeller cuts
Well, look at the picture above and isn’t it shocking! Not sure about you but it definitely hit me hard and just can’t imagine the amount of pain and suffering the shark must be going through. Most sharks come and go in Oslob but around 4% of the sharks become year round residents and this poses problem for the sharks as they might take advantage of the free food and become less sensitive to dangers For instance, about half of the whale sharks in Oslob have propeller cuts on their bodies (Warne, 2018) which mean they might have approached a shark-fishing vessel since the whale shark tourism only uses hand-paddled vessels. This makes the sharks more prone to external dangers such as poaching since they equate that boats means there is the presence of food.
Reasons why feeding whale sharks does more harm
The sharks who become year-round residents are evidence of provisioning. The provision of food to increase sightings has been a controversial practice as provisioning has effects on increasing aggression, change in movement patterns, reduction in offspring survival rates and disrupt foraging especially during non-provisioned periods (Thomson et al., 2017).
Peak whale shark season at Oslob where whale shark tourism takes place coincides with times of the year when sharks are not present in other non-provisioned sites which means that the sharks are attracted by the supplemental food source. Provisioning of juvenile sharks has the ability to negatively influence the population as prolonged residency means less time foraging in nature and learning the patterns of prey distribution (Thomson et al., 2017). This increases the dependency on provisioning even in the later stages of their life.
Coral reef degradation
Detrimental impacts on coral reefs
Also, whale shark tourism causes reef degradation as coral community structure is likely to be affected by human activities and therefore lead to an overall reduction in coral species richness and diversity (Wong et al., 2019). Changes in coral composition also indicates environmental stressors. Tourism activities also lead to a decline in coral cover and increase in macroalgal cover. The prevalence of coral diseases are 15 times more common where there are tourists as compared to locations with no anthropogenic disturbance (Wong et al., 2019).
Wastewater disposal
Wastewater disposal and land use changes due to tourism cause water quality deterioration due to the increase in dissolved nutrients and depletion of dissolved oxygen (Wong et al., 2019). Human waste produced by tourists also cause localised nutrient spikes which promote algal production (Wong et al., 2019).
In conclusion, although there are rules and regulations to minimise the direct impact of humans on the sharks such as physical contact, often, it is the indirect impacts of humans that have devastating outcomes on the sharks. Hence, the scale of whale shark tourism should take into account much more deeper issues like whether the feeding of sharks cause more harm than good and also the assimilative capacity of the coral reef ecosystem. Furthermore, it is worth noting that although whale shark tourism brings about huge revenue, the long term impacts on sharks are not/ poorly understood and hence should be treated with caution.
References
Thomsen, M. (2019, November 19). Manta rays and whale sharks in Indonesia are consuming 63 PIECES of plastic pollution per hour. Retrieved October 26, 2020, from https://www.dailymail.co.uk/sciencetech/article-7703541/Manta-rays-whale-sharks-Indonesia-consuming-63-PIECES-plastic-pollution-hour.html
Thomson, J. A., Araujo, G., Labaja, J., McCoy, E., Murray, R., & Ponzo, A. (2017). Feeding the world’s largest fish: highly variable whale shark residency patterns at a provisioning site in the Philippines. doi:https://doi.org/10.1098/rsos.170394
Warne, K. (2018, August 30). Inside the Chaotic World of Whale Shark Tourism. Retrieved October 25, 2020, from https://www.nationalgeographic.com/animals/2018/08/whale-sharks-tourism-philippines-benefit-harm-news/
Wong, C. W. M., Conti-Jerpe, I., Raymundo, L. J., Dingle, C., Araujo, G., Ponzo, A., & Baker, D. M. (2019). Whale Shark Tourism: Impacts on Coral Reefs in the Philippines. Environmental Management, 63(2), 282-291. doi:10.1007/s00267-018-1125-3