The source of 60K for the tuna must be Bikini Atoll and not worldwide fallout because we analyzed tissues from 214 tuna, including 75 yellowfin tuna, taken from the Japanese tuna fishery during 1968 and 1969, and found no 6006 (NVO-269-7, Annual Report). In contrast, the 5° Fe concentrations in the dark muscle of the tuna from the Japanese fishery ranged from 3.3 to 1600 pCi/g dry, most of the values fell in the range of 101 to 500 pCci/g dry. ' of the 55 It appears, therefore, that a major amount Fe in the Bikini tuna is from worldwide fallout. One of the principal sources of radionuclides at Bikini is Bravo Crater in the reef adjacent to and southwest of Nam I. Figure 1 shows a gamma-ray spectrum of sediment taken from a depth of 160 feet. Clearly, 6000 and 20755 predominate among the gamma emitters. In most soils, 1374, is the most abundant radionuclide. An intermediate condition exists at the southwestern end of Eneman I., where a low area is occasionally overwashed by seawater, and at the high tide line, where the 137a5 is being leached from the soil. The retention of 066 and 207 54 by the sediments is reflected in the fact that the bottom-feeding goatfish in the vicinity of the craters contain ten times more 6005 than the herbivorous convict surgeonfish and plankton feeding mullet. However, some 60K is” being transported eastward by the bottom current in the lagoon either in solution or associated with fine (colloidal?) particles, because the difference in 6006 con- tent between convict surgeonfish and mullet in the vicinity of Bravo Crater and 16 miles eastward near Bikini I. 5001390 is only by a a factor less than two. at of Enetay MRECHIVES pepartme u's office