-14- The zn65 peak at 1.12 MEV occurred in every tissue sample tested, indicating the common occurrence of this isotope compared with other gamma emitters. This radioisotope has been observed in fish tissues by many authors, as summarized by Lowman et al. (1957). Additional data from this Laboratory are given in Table 4. ; The Coo? peak of 0.12 MEV was present in the liver of all fish tated. however, it appears to be rather omnivorous fish taken at Rongelap Island. low in the liver tissue of This radioisotope was not detected in goatfish gut or goatfish bone, but occurred in small amounts in goatfish muscle. No distinct peak at 0.12 MEV appeared in the muscle tissue of reef fish or in halfbeaks taken at Kabelle Island. The peak of Mn°4, at 0.84 MEV, was partially obscured by the Co58 peak at 0.81 MEV. One or both of these radioisotopes present in the muscle and liver of reef fish from appeared to be Enibuk Island, in muscle and liver of halfbeaks from Kabelle Island, the and possibly were present in the muscle of reef fish from Kabelle Island. Verification of the presence of both of these isotopes in Enibuk reef fish liver was later obtained by ion-exchange resin column analysis (see below). The Co0 peak at 1.17 MEV was obscured by the Zn§9 peak at 1.12 MEV; however, the C050 peak at 1.33 MEV was observed in the liver and muscle of Kabelle goatfish and in the liver of Rongelap omnivorous fish. The presence of Co60 was also later verified by ion-exchange analysis of Enibuk reef fish liver. . pry ou ( yy be 2K 2