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Whale Sharks: The Iconic Species of Mafia Island, Tanzania

A Pristine, peaceful coastal tourism destination, Mafia Island is the only home for the whale sharks in Tanzania. Located 20 kilometers offshore from the eastern extent of the Rufiji delta on the southern coast of Tanzania. The 822 km2 Island’s Marine Park, provides an ideal and calm environment for a vast range of marine species. Mafia is one of the administrative districts in the Coast Region in Tanzania mainland. The size of the island is 435 km2 with a population of 46,850 as of 2012. 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.

Whale sharks, the underwater gentle giants of the sea, are neither typically whales nor sharks. They do not have proper teeth, they are social, calm and are not predators. This is what makes whale sharks popular for marine wildlife tourism. They are the biggest recorded fish in the ocean globally. Swimming alongside the whale sharks is amusing. A respectful distance is required during swimming in order not to annoy the whale sharks and make them nervous. They are born at 40-65 centimetres and reach adulthood at up to about 22 metres. An adult whale sharks can measure up to around 20 meters long, weigh around 20 tonnes with some reaching up to 34 tonnes and have a potential to live up to 70 years. The current population is recorded to be 206 in December 2019 compared to approximately 100 individuals in 2012. Can we add here how individual whale sharks are recognized?
The best season for whale shark sighting is from October to February each year. November and December is the most reliable time for whale sharks sighting at Mafia Island. During peak season whale sharks can be easily seen nearshore. The Rufiji River feeds the Mafia Channel with nutrients and planktonic organisms on one side while the Mafia Island Marine Park do the same from the other side. Together they make the channel productive with abundant of food which attracts and feeds the whale sharks. As filter-feeders, whale sharks swim with the mouths open consuming multiple kilograms of planktons and small aquatic organisms each day. Some individual sharks have been spotted each year since 2012. Many sharks spend years, or even decades, close to the island.
Whale sharks are iconic species for Mafia District. They are the major attraction of tourism and one of the key sources of income for the community and Mafia District Authority. Whale sharks are protected and are listed in the IUCN red list of Endangered, Threatened and Protected species. They were categorized as endangered species 2016. Their vulnerability is mainly due to slow growth where they become mature at the age of 30 years, and therefore if not well managed they may become extinct. Communities engage in whale shark tourism as tour operators, tour guides and boat riders. A network of whale shark tour operators (WATONET) has been established and is going to be an important contact point on whale shark tourism. The local authority oversees implementation of polices and legislations and collects tax from tourism.

WWF in collaboration with the Government Authorities supports the effective management of this species and joint measures are being promoted to safeguard the whale sharks of Tanzania. Since early 2012 WWF facilitated awareness raising to the stakeholders about the importance of coordinated management of whale sharks in Mafia. This included fishers, boat riders, tour operators, tour guides, district authorities, hoteliers and other investors on the island. This resulted into development of whale shark management strategy and the code of conduct for whale sharks in 2018. Further actions are needed to advance management and monitoring of whale sharks including implementation of the management strategy. More research is needed to monitor trends during low season when whale sharks migrates off Mafia nearshore. During the same year WWF Tanzania commissioned a study in collaboration with a group of researchers from the Marine Megafauna Foundation to find the facts and monitor the life of the whale sharks in Mafia. Monitoring is undertaken once every year during the peak season to report the trends.
Threats that put whale sharks at risk include entanglement in fishing nets; injuries caused by boat rides and hunting for meat and fins. However, the Mafia community do not have a record of hunting whale sharks but rather there is some conflict between sharks and fishers. The Lucifer shrimps that attract the whale sharks are also important prey for small anchovies and mackerel which are targeted by fishers.  During the season fishers and the whale sharks meet at the fishing ground and that is where conflicts occur. Even if fishers are not trying to catch the sharks, but their large ring-nets can trap, entangle and injure the whale sharks. Sharks can get amputated especially the fins during untangling from fishing nets.
The whale sharks are protected by law in Tanzania. They are seasonal at the surface and their feeding grounds are generally predictable. It is proposed that a management zone be created where sharks can feed safely with minimum interactions with the local fishing and boating activities. High whale sharks’ residency in Mafia has boosted tourism to double since 2012; more people are employed by the coastal tourism industry. There is excellent potential for the island to develop as a marine ecotourism destination.
Commemoration of the International Whale Shark Day for this year 2020 will be celebrated in Mafia Island where WWF and partners have organized a series of events from 28-30 August.
© Clare Prebble - Marine Megafauna Foundation
Whale shark in the Mafia Island

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