These were probably constructed from Arab information. The first European to visit the inland Zambezi river was the Portuguese degredado António Fernandes in 1511 and again in 1513, with the objective of reporting on commercial conditions and activities of the interior of Central Africa. The final report of these explorations revealed the importance of the ports of the upper Zambezi to the local trade system, in particular to East African gold trade. The first recorded exploration of the upper Zambezi was made by David Livingstone in his exploration from Bechuanaland between 1851 and 1853. Two or three years later he descended the Zambezi to its mouth and in the course of this journey found the Victoria Falls. During 1858–60, accompanied by John Kirk, Livingstone ascended the river by the Kongone mouth as far as the Falls, and also traced the course of its tributary the Shire and reached Lake Malawi. For the next 35 years very little exploration of the river took place. Portuguese explorer Serpa Pinto examined some of the western tributaries of the river and made measurements of the Victoria Falls in 1878. In 1884 the Scottish-born Plymouth Brethren missionary Frederick Stanley Arnot traveled over the height of land between the watersheds of the Zambezi and the Congo, and identified the source of the Zambezi. He considered that the nearby high and cool Kalene Hill was a particularly suitable place for a mission. Arnot was accompanied by the Portuguese trader and army officer António da Silva Porto. In 1889 the Chinde channel north of the main mouths of the river was seen. Two expeditions led by Major A. St Hill Gibbons in 1895 to 1896 and 1898 to 1900 continued the work of exploration begun by Livingstone in the upper basin and central course of the river. The population of the Zambezi river valley is estimated to be about 32 million. About 80% of the population of the valley is dependent on agriculture, and the upper river's flood plains provide good agricultural land. Communities by the river fish it extensively, and many people travel from far afield to fish. Some Zambian towns on roads leading to the river levy unofficial 'fish taxes' on people taking Zambezi fish to other parts of the country. As well as fishing for food, game fishing is a significant activity on some parts of the river. Between Mongu and Livingstone, several safari lodges cater for tourists who want to fish for exotic species, and many also catch fish to sell to aquaria.