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All You need to know about the biggest epic fish: The whale shark

International whale shark day is celebrated every 30th of August across the globe. It has been designed so that we can celebrate and increase awareness about these amazing sea-dwelling creatures. WWF Tanzania has been engaged in the conservation of whale sharks for more than 10 years. Joan Itanisa gives an interesting overview of these epic individuals and the conservation efforts in the Mafia Island

Whale shark with researcher
© Chris Rohner
Whale shark with researcher

Reputed for being among the ugliest creatures of the deep sea many will assume that they are ferocious and dangerous, scary even! Well you are in a big surprise! Everything about them is intriguing, fascinating and totally the opposite of what many would have thought.
Let’s start with their name; Whale Sharks. Are they whales? Sharks? Truth is these giants are actually sharks. Many of us when we hear shark we see danger, but surprise, surprise these sharks are among the many species of sharks that are not dangerous at all, these sharks are actually called the gentle giants of the seas. They are the biggest fish to ever grace the waters of the seas around the world. Although they are sharks, they have a lot of similarities with the whales. They are huge like whales and feed just like whales instead of their shark relatives.
Confused? Hold on a while longer, more fascinating facts are listed below

Lets go back to being ugly, this also remains to be a 50/50 thought as some see these gentle giants as among the most beautiful see species with their epic lines and dots that are unique foe each individual. 
An adult whale shark can measure between 12 to 18 meters. The biggest individual found a few years ago was 18.8 meters long, more speculation says they can grow even up to 20 meters! This is almost as big as a big school bus! 
Although they have thousands of small teeth, they never use them to chop, bite or chew their food. They are called filter feeders. They feed on planktons and small shrimp and fish. Their feeding is laborious. Because of their size they eat large amounts of plankton and the small fish. It is estimated that a juvenile whale shark will eat around 21 kilograms per day. For them to be able to feed they have to swim long distances with their mouths open to collect their food through filtering and uses their gills to process about 6,000 litres of water in the process.  
Longevity: It is thought that less than 10% of whale sharks born survive to adulthood but those who survive can live up to 70 years! They mature for reproduction at 30 years 
Due to their humongous size, they are slow swimmers, they are said to swim at least 4.8 kilometers per hour. Surprising they have stamina to swim long distances, they can migrate thousands of miles to different feeding grounds 
There is very little literature around the reproduction in whale sharks. The little information we have is whale sharks are ovoviviparous which means their eggs are hatched in the female’s womb and they can produce around 300 younglings at a time. The baby whale sharks are usually left to fend for themselves while very young. 
Whale sharks can be found in all temperate and tropical oceans around the world, except the Mediterranean Sea. They are migratory and will usually move to where the food is or where there are good conditions for their reproduction.
Did I tell you about their weight? Of course, a fish as big as this will definitely weigh a lot, it is estimated that a grown-up female whale shark can weigh up to 26 tonnes even more.
 

Whale shark
© WWF UK
Whale shark

Whale sharks as ugly as some will perceive them, they are key tourism attractions in some of the areas in the world. Apart from being gentle whale sharks are also playful and this will usually make swimming with them really easy and interesting. Tanzania is also a home to whale sharks. Found only in the Mafia Island the whale sharks will usually grace the Mafia waters through the months of October to February, with November and December being the best months for a swim with these gentle giants. Whale shark tourism has become a key source of government income through Marine Wildlife tourism in Mafia bringing in more than 80 million Tanzania shillings per annum. They also help in creating jobs to thousands of community members in Mafia including tour guides, boat riders, hoteliers etc.
 
One may wonder why the whale sharks chose the Mafia Island as their home, truth is being giants they need a lot of food, and this is plenty in the Mafia Island. There is a  high food production off the Mafia channel. When food production is low the sharks move slightly off Mafia and a bit deeper. Whale sharks in the South Western Indian Ocean are known to stay longer in Mafia Island waters and acoustic tracking proves that the population is resident in the area, meaning they do not migrate completely outside Mafia waters. Some individuals have been spotted to come back to Mafia for decades.

Whale shark
© Joost Van Uffelen
Whale shark

Sadly, these gentle giants have been in danger of extinction in many areas in the world Tanzania included. They are hunted for their gills, blood especially by fishermen to paint their vessels and sometimes for their meat which is plenty unfortunately. Most especially this happens in the Asia region but indeed affects the whole world.
The exact number of whale sharks available today is not quite clear with some estimating to be around 200,000 globally. But one sure fact is that in the last 75 years, the number of these gentle giants has declined to about 50%. In Tanzania back in 2012 there were less than 100 individuals in the waters of the Mafia Island. The International Union for Conservation of Nature (IUCN) has identified whale shark as endangered species and indeed strategic actions and management need to be taken to protect the gentle giants. In Tanzania whale sharks are protected by law and today even fishers take great care of the whale sharks by making sure they are not caught by their nets and when this accidentally happens, they are fast to disentangle them and set them free
 
WWF Tanzania has been working in collaboration with the government to improve the management of the whale sharks while working to increase their numbers. This has included awareness raising about the importance of protecting these iconic species of the Mafia Island among different groups including school children, fishers, boat riders, tour operators, tour guides, district authorities, hoteliers and other investors on the island. This resulted into the development of whale shark management strategy and the code of conduct for whale sharks in 2018.
 
WWF is also supporting the study of the whale sharks in the Mafia Island to monitor trends during low season when whale sharks migrate off the Mafia nearshore. Working with a group of researchers from the Marine Megafauna Foundation facts on the life of the whale sharks in Mafia is undertaken once every year during the peak season. And this year as we celebrate the whale shark day, we are excited to report that whale shark numbers has increased to 215 in 2021!
Now that you know will you be ready to swim alongside these epic controversial giants? Remember to keep a respective distance as you two swim together so they are not getting nervous and leave you alone. But most importantly become a partner in the protection of the whale sharks by taking just a few actions: Reducing the use of plastics especially single use plastics as these usually end tin the ocean, take time to share and raise awareness with your colleagues and join us in the celebration of whale shark day which is celebrated every 30th of August.
Happy Whale Shark Day!
 

Quick Whale shark facts
© WWF Tanzania
Quick Whale shark facts