Mafia Island (Kisiwa cha Mafia) is an island and district of Pwani Region, Tanzania. The island is the third largest in Tanzanian ocean territory, but is not administratively included within the semi-autonomous region of Zanzibar, which has been politically separate since 1890. Mafia Island forms the major part of Mafia District, one of the six administrative districts in the Pwani coastal region. The local archipelago and the main island are sometimes called Chole shamba in Swahili, hinterlands of the former maintown of Chole on Mafia Bay. The island's population is over 40,000. The economy is based on fishing, subsistence agriculture and the market in Kilindoni. The island attracts some tourists, mainly scuba divers, birdwatchers, game fishermen, and people wanting relaxation. Geography Mafia Island, (), lies off the east coast of Tanzania opposite the delta of the Rufiji River. The wide stretch of water between the delta and the island is called the Mafia Channel. Mafia Island is part of a small archipelago with several much smaller islands, some of which are inhabited. The main town on Mafia is Kilindoni on the west coast. On the east coast is Chole Bay, Mafia's protected deep-water anchorage and original harbour. The bay is studded with islets, sandbanks and beaches, and is protected from the east by reefs and Juani Island. The northernmost point on the island is a coral cliff rising approximately above the sea called Ras Mkumbi, beyond the cliff the land gradually rises to . There is a lighthouse at Ras Mkumbi. Geology Mafia Island, and the associated archipelago were formed by rifting and uplift of part of the continental shelf during the Pleistocene. Ecology The main ecosystems on the island are mangrove swamps, coastal forests, scrublands, and grasslands. Birds A 115,000 ha area, encompassing Chole Bay, the southern coastline of Mafia and its associated smaller islands, along with the intervening marine waters, has been designated an Important Bird Area (IBA) by BirdLife International because it supports populations of western reef egrets, Terek sandpipers and crab plovers. Mammals Mafia Island is home to fruitbats (flying foxes) of the genus Pteropus. Climate Mafia Island has a tropical climate. This climate is classified as "Aw" by the Köppen-Geiger system. The average temperature in town of Kilindoni is . The average annual rainfall is 1,705 mm. The monthly average temperatures are usually between . There is one major rain season, with most rainfall coming