Whale shark, though sometimes misunderstood as whales, are in fact sharks- the biggest ones in existence. It is also the largest fish alive. Whale sharks are found in oceans all over the world but are concentrated in tropical oceans. They are found in regions of The Indian Ocean and The Atlantic Ocean. These gentle giants are enormous and can be as long as 59 feet. On an average they weigh 15 tons. Their phenotype is very distinctive- white spotted colouration all over its body. This feature makes them easily recognisable to snorkelers and divers when they aggregate at the shores.
What makes the whale shark unique?
The whale shark is one of three filter feeding fish on the planet. They forage for food at the surface of the ocean. The sharks periodically appear at the top of the ocean with their mouths wide open, allowing large amounts of water to enter. They have almost 3000 tiny teeth lining the insides of their mouth, but they are vestigial, and do not play a role in feeding. The water that enters the mouth is filtered through gill slits, which act like a sieve, retaining small organisms like zooplanktons, small molluscs and fishes.
The filtered sea water returns to the ocean. The sharks close their mouths at regular intervals to swallow their prey. Another very interesting aspect is the fact that they do not pose danger to humans. This makes it easy for scientists to study their behaviour and physical adaptations underwater. Out of curiosity, they approach divers or boats but cause no harm to them.
After its discovery in 1828, for decades it was a shark that was not often seen. They were found off the South African coast initially and took almost a year to be described as the largest living shark by Dr. Andrew Smith. Whale sharks are highly migratory in nature. Their migratory patterns are understudied but so far, marine biologists have found that they migrate along the Gulf of Mexico and the north-eastern Yucatán Peninsula and the Caribbean between May and September every year.
Little is known about the Whale Shark
Migration patterns are being studied through tagging and satellite imaging. The objective of migration is probably better foraging landscape and suitable mating and birthing grounds. Natural events and geography impacts productivity. Warm waters though favourable are sometimes nutrient poor as compared to colder waters. This could be attributed to effects of climate change on the chemical content of the sea water and marine species present. Scientists still have a long way to go as far as studying their reproductive biology goes. There has only been one pregnant whale shark observed so far, therefore clarity on mating, birthing, calf size and characteristics are unknown.
What are some threats to whale shark?
Although there is no accurate population statistic on the whale shark, they were listed as endangered by the IUCN due to various reasons. What led to the decrease in their populations? Initially, whale sharks were mere by catches, but now the demand for whale shark meat has gone up. They are highly valued in the international market. Their meat, fins and oil continue to be exploited through illegal and unregulated fisheries. Their skin is used for bags. Unfortunately, whale shark tourism has also contributed to their decline.
Tourism proves problematic
Contrary to what we expect the tourism outcome to be, the whale shark tourism, prominent near the southern tip of Cebu Island of the Philippines, is an industry powered solely by man’s selfish interests. The island is not a natural habitat for the sharks and therefore they get fed by the locals and fishermen of the area, guaranteeing their arrival for sightings for tourists. Tourists are instructed not to come in close proximity of these sharks and not to touch them but more often than not, they are found to break these rules. This shark watching operation makes us question, have humans taken a little too much control over wildlife? Should wildlife tourism be banned?
Whale Shark Biology does not help their case!
With lifespans as long as more than 100 years, they are literally dying at a faster rate than they are reproducing. Why is the whale shark important to the ecosystem and what would happen if it disappeared from the face of Earth? Whale sharks or any of the larger sharks or whales are top or apex predators, meaning they occupy the highest position in the food web and do not get preyed on. Scientists have found that if apex predators go extinct, their prey population increases exponentially.
Prey species declining as well!
The prey population then ends up using up all its food resources. As far as the whale shark is concerned, their extinction could lead to increase in zooplankton population to detrimental levels. An overgrowth of zooplankton can be harmful to all marine organisms. It can lead to formation of algal blooms that have toxic affects on fishes, molluscs and humans that eat these fishes.
What is being done to save the whale shark?
Whale sharks have become a priority, with their numbers still on the decline, but there are ways in which both conservationists and the common man can help protect this species. Several research projects and programmes have been up and running, concentrating all efforts to conserve them. A conservation campaign was kickstarted by The Wildlife Trust of India in Karnataka on August 30th, 2022, which is celebrated as International Whale Shark Day.
There are other ways in which citizens can contribute to whale shark protection-first and foremost being educating yourself on whale sharks. Respecting the oceans and stopping single use plastic usage are also extremely important. Reducing seafood consumption helps as this ensures adequate feeding resource for marine fishes. This can be achieved through consumption of sustainable seafood as well. And if you are fascinated and want to go whale shark watching, make sure you do so in their natural habitats. With so many ways to help conserve these gentle giants, what’s stopping you?
Written by Manasa Ramesh
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References
1. https://www.jstor.org/stable/24333963?read-now=1&seq=7#metadata_info_tab_contents
2. https://www.britannica.com/animal/whale-shark
4. https://www.worldwildlife.org
6. https://www.gviusa.com/blog/international-whale-shark-day/
8. https://www.americanoceans.org/blog/why-are-whale-sharks-endangered/