Most of the species selected were reef dwellers and more or less sedentary; however, a few which prefer open sandy bottom, as goatfish, such jacks and flatfish, were also taken and ashed for counting. The fish which best fulfilled the criteria listed above were the damsel fish (Pomacentridae), surgeon fish (Acanthuridae), groupers (Serranidae) and wrasse (Labridae). Appendix Table 3, which summarizes the material used in the analysis for redioactivity, shows that these four families were taken at all stations. Certain species such as the grouper, Epinephalus merra, the damsel fish, Abudefduf biocellatus, the surgeon fish, Acanthurus triostegus, and the wrasse, Halichoeres trimaculatus, were taken at a majority of the stations. A total of 237 specimens representing 58 species, 33 genera and 22 families of fishes were counted for radioactivity on 768 plates. The following organs of the large specimens selected were analyzed for radioactivity: gut (including contents). combined for analysis: and liver; muscle, skin, bone, liver, and In small fish the following were (1) muscle, skin, and bone; (2) gut or (3) entire fish. Omnivores and carnivores were selected in approximately equal numbers at each station. In order to compare the activity found in various samples of entire fish, the total activity per gram of an individual fish was calculated as the sum of the activity of tissues, the procedure followed in 1949 (AEFCD-3446). Sults are recorded in Table 10. - 44 - all The re- The tissues listed in this