the development of the industry in the islands. The Japanese entrepreneur Haruji Matsue arrived on Saipan in 1920 and formed the South Seas Development Company, which became the largest commercial enterprise in Micronesia. He significantly expanded the quantities of sugar cane produced in the islands, with over under cultivation by 1925. By the early 1930s the sugar-related industries accounted for more than 60% of the mandate's revenues. At its peak the company maintained over of sugar plantations using tenant farmers, as well as operating sugar mills on Saipan, Tinian and Rota. Bananas, pineapples, taro, coconuts, manioc, coffee and other tropical farming products were also grown, putting the islands on a par with Taiwan. The islands also provided bases for the Japanese fishing fleet which was centred at Koror. Fishing formed one of the most profitable industries in the islands. Large fleets of boats were used and fish processing plants were set up on many islands. Harbour improvement works were undertaken at Tanaha (Japanese: 棚葉) in Saipan and Malakal Island in Palau in the late 1920s. By the end of the 1920s the mandate became self-sufficient, no longer needing subsidy and financially contributing to the Japanese Empire. The phosphate resources of the islands were exploited by Japanese mining companies, which took over the German phosphate mines on Angaur island and expanded them. Smaller phosphate mines on neighbouring islands were also opened. Total exports to Japan eventually reached around 200,000 tonnes per year. Angaur island alone produced some 60,000 tonnes per year. The phosphates were used for farming. Bauxite was another mineral product of the colonial economic structure, although the mineral was only present in the Palau group. In 1937 the mother-of-pearl industry became lucrative and large quantities of pearls, both natural and cultured, were extracted from the islands. The South Seas Trading Company had an exclusive contract from 1915 with the IJN to provide freight, passenger, and mail services to the Empire as well as between the islands. The route between the Empire and the islands was subsequently taken over by the Japanese Mail Steamship Company (Nippon Yusen Kaisha), the largest steamship line in the Empire. The luxurious amenities offered on board some of the company's vessels brought about the beginning of Japanese tourism to the islands. The flying boat was the principal type of aircraft used for commercial aviation due to the shortage of flat land available for airfields. Imperial