ash of tuna. that time, ‘This was less than one percent of the permissible level at Although the activities were too low for accurate radio- chemical analyses, the strontium-90 levels in the edible portions of fish were less than two percent of the permissible. level at that time. For these open ocean surveys, the radioactivity in fish was less by factors of 10 o¢ more than for fish at Eniwetok or Bikini Atolls, but was several to many times as much as for fish from Puget Sound, an area then considered to be free from fission product contamination. The next oceanic survey was conducted during June and September 1956 during the Redwing series. The cruise zig-zagged west of Bikini Atoll and Eniwetok Atoll to collect plankton samples (Hines, 1962, p. 223; and Lowman, 1958). layer. The fallout was found not to have penetrated the surface Since megaton explosions had occurred at Bikini Atoll, radioacLlivity was high. Although the greatest radioactivity found for plankton was 1.2 million d/min-g north of Bikini, the minimum level of 1,300 d/min-g was almost as high as the maximum level recorded in Operation Troll in 1955. Another cruise on the ship Marsh acted as a sequel to the Shunkotsu-Maru by covering approximately the same sea area in attempting to follow the Redwing contamination in September 1956. At these later times after nuclear explosions and at these greater distances, the radioactivity in plankton was lower. The. maximum was 21,000 d/min-g eighty miles north of Eniwetok. | For Operation Hardtack in 1958, the U.S.S. Rehoboth was used for radioactivity observations (Hines, 1962, p. 275). Plankton radioactivity was as high as 32 million d/min+g following the Wahoo underwater explosion on the ocean side at the south of Eniwetok Atoll. 20 Fish, shrimp, and