Tuna fishing activity in post WW II in Micronesia was remarkably different. Much of the fishery infrastructure and tuna vessels were destroyed by war activity and the Japanese and Okinawan fishermen had been repatriated. Under a United Nations trustee arrangement, the United States assumed control of the area, but had much less interest than Japan did previously in economic development, including fisheries. As part of the terms of surrender, geographic restrictions known as MacArthur Lines, were placed on the movements of Japanese vessels, which effectively prevented their tuna fishing in Micronesia. These lines were extended four times and finally the last MacArthur Line was lifted in April 1952, at which time the Japanese government began encouraging the construction of large longline and pole-and-line tuna vessels (Peatie, 1988; Matsuda, 1987). Nine Japanese longline/mothership expeditions took place in Micronesia in 1950 and 1951 under temporary permission of the USA military (Felando, 1987). Although Japanese fishing activity in what were then high seas areas gradually returned to the Micronesian region, USA government restrictions on economic activity ashore were held in place until the mid-1970s and precluded any return to the fish processing bases developed before the War.
In the early 1950s the activities of the Japan-based pole-and-line vessels were limited to fishing close to Japan by their need to carry live bait, but later improvements in technology allowed those vessels to increase their range from their Japanese bases. By the early 1960s Japanese pole and line vessels were fishing in the areas near the northern Marianas and Palau during their near-Japan off-season (Rothschild and Uchida, 1968; Skipjack Programme, 1984) and during the next ten years were fishing well south of the equator. Longline vessels also expanded their range; in 1952 their fishing area included most of Micronesia and by 1962 most parts of the Pacific between 40o north and south latitude had been explored by Japanese longline fishermen (Matsuda, 1987). Significant American tuna initiatives were also under way. During World War II the USA government commandeered 49 California-based tuna pole-and-line vessels for service in the Pacific. Over 600 tuna fishermen served on these vessels. This activity was apparently quite instrumental in creating awareness in American tuna fishermen of the size and fishery potential of the western Pacific region, and for the first time introduced them to previously unheard of places like the Marshall Islands, Micronesia, the Solomon Islands and Palau.
During the late 1940s and early 1950s exploratory cruises were carried out by USA tuna vessels. These expeditions used pole-and-line, longline, and purse-seine vessels that were both privately and government sponsored to do exploratory tuna fishing in the Line Islands of Kiribati, the Society Islands of French Polynesia and from the Marshall Islands to Palau (Felando, 1987). This was followed by other major American initiatives: the establishment of the Van Camp Seafood Company tuna cannery in Pago Pago, American Samoa in 1953 (see section below on canning), followed by the StarKist cannery in Pago Pago in 1963 and the Van Camp pole-and-line base in Palau in 1964. That base had from 8 to 15 pole-and-line boats and a freezing facility (Skipjack Programme, 1984).
The Japanese were also active in establishing facilities in the Pacific Islands area. Between the early 1950s and the early 1960s, tuna longline bases were established in Pago Pago (American Samoa), Santo Island (Vanuatu), Noumea (New Caledonia), Papeete (French Polynesia) and Levuka (Fiji). In most cases these facilities supplied raw product, mainly albacore, to canneries in Hawaii and the USA mainland (Doulman, 1987). At the same time, the Japan-based pole-and-line vessels continued to expand their range, with fishing operations eventually reaching even the southern parts of the Pacific Islands area, with 300 pole-and-line vessels participating seasonally in the fishery.
Quasi-government foundations played a major role in both the Japanese and American tuna ventures in the Pacific Islands. To promote Japanese foreign-based tuna fisheries, the Overseas Fisheries Cooperation Foundation (OFCF) and the Overseas Cooperation Foundation (OCF) provided technical and economic assistance. OFCF and OFC loans cover 70 percent of the capital required by joint ventures (Matsuda 1987). American tuna initiatives in the Pacific Islands region received support from the Reconstruction Finance Corporation (late 1940s), the Pacific Oceanic Fisheries initiative (1949–1959), and Pacific Tuna Development Foundation (starting in 1974).