Other than those in the Red Sea, the only pearl resources in Africa which have received attention are on the eastern coast, south of the Gulf of Aden. Little information exists as to the origin of these fisheries. In a paper published by the Lisbon Geographical Society, January, 1903, Señor Ivens Ferranz states that, according to tradition, in remote times the Ibo Archipelago, on the northeast coast of Portuguese East Africa, was inhabited by a Semitic colony, which located there to fish for pearls, and these were carried through the Red Sea to King Solomon. He adds that there is little doubt that, after the great emigration which started from the Persian Gulf in 982 and founded Zanzibar, Kilwa, and Sofala on this coast, some Arabs engaged in fishing for pearls about the islands near Sofala. In 1609 Joao dos Santos wrote that on the sandy sea bottom about the Bazaruto Islands, which are about 150 miles south of Sofala, there were many large oysters which bore pearls, and the natives fished for them by diving in practically the same manner as in the Persian Gulf.[182] In a personal memorandum, Sir Robert Edgcumbe states that in the very early times of Portuguese exploitation on the eastern coast of Africa, pearl fishing was carried on in these waters. For a long period the tenure of power exerted by the Portuguese was of a feeble character; they practically occupied no position of importance on the mainland, but seized upon stations on the islands which offered decent harbors. Thus their chief settlements, such as Mozambique and Ibo, were on islands lying off the coast, and until recent years they made no serious attempt to occupy the mainland. Arabs and Banyans carried on the commercial traffic of the country, as they still do, and they were more truly the masters of this coast than were the Portuguese, who were little more than nominal rulers. Trading to and from India in their small dhows, the Arabs and Banyans had full knowledge of the value of pearls, and undoubtedly secured all that were obtainable. But they observed no restrictions, and without doubt—for a time, at any rate—greatly impaired the productive power of the fisheries. The principal pearl reefs of East Africa, so far as known at present, extend along the coast of the German East African territory from the Province of Uzaramo to the Rovuma River, the southern limit of that territory, and also into Portuguese East Africa as far south as Pemba Bay, a total distance of about 300 miles. Along much of this coast, there are islands lying from one to two miles off shore, and between these islands are barriers of reefs, which create a series of lagoons. In these lagoons, protected by the islands and the reefs from the influence of the surf formed by the Indian monsoons, there are large patches of coral rock and groups of living coral, which form excellent attachments for the pearl-oysters.