RADIOACTIVITY IN THE REEF FISHES OF BELLE ISLAND, ENIWETOK ATOLL, APRIL 1954 TO NOVEMBER 1955 Introduction Previous studies of the radioactivity in the fishes in the Marshall Islands have been confined to single surveys made soon after &8n atomic detonation, occasionally followed by one to three resurveys a few months up to three years later (UWFL-7, UWFL-16, UWFL-19, UWFL-23, WT-616 (UWFL-33), and UWFL-43 ). Trends in the levels or decline of radioactivity in the fish populations could only be estimated by basing assumptions on physical decay. The purpose of this investigation was or decline of radioactivity in the fish, in different species, the environment and to measure the to compare the decline in some of the organs or tissues, to compare trend the decline with the and in physical decay of radioactivity. Materials and Methods Continuous, sequential studies of the amounts of radioactiv- ity in the reef fishes of Belle (Bogombogo) Atoll, 1954, were made from April 14, Island, Eniwetok through November 1, 1955, during and after the weapons testing program at Eniwetok and Bikini Atolls. The Nectar important in these studies, shot of May 14, 1954, wag the most since the detonation occurred but