Gulf of Mannar, arm of the Indian Ocean extending east to west between India and Sri Lanka at a width of 160 to 200 km (100 to 125 mi). The gulf receives the Tambraparni River from the coast of India and the Aruvi Aru from the coast of Sri Lanka. 117 hard coral species have been recorded in the Gulf of Mannar. Sea turtles are frequent visitors to the gulf as are sacred sharks, dugongs, and dolphins. However, the combined effects of 47 villages, with a total population of around 50,000 has meant that overharvesting of marine species has become a problem. Fish catches have declined, as have pearl oyster, gorgonian and acorn worms populations. Local fishermen rely on the reef to feed their families however destructive fishing methods combined with the stress of pollution and coral mining have meant both nearshore and offshore catches have decreased. Located on the southeastern tip of the subcontinent, the Gulf of Mannar is known to harbour over 3,600 species of flora and fauna, making it one of the richest coastal regions in Asia. Among the species that figure in the endangered list include dolphins, sea cow (Dugong Dugon), whales and sea cucumbers.