-24~ given in Table 3 are based :ipon the calculated activity of the samples at the time of collection. Levels of strontium-90 The results of the Sr90 determinations of plankton and a shrimp sample are given in Table 4. The only pre- Wahoo plankton samples that contained detectable amounts of Sr9° were samples P-6 and P-7, collected on the same day the Cactus device was detonated. P-8 and P-12, Samples collected 19 to 80 hours later, contained no gr90, The plankton samples collected after Wahoo, however, contained levels of Sr9° that comprised from 0.0001 per cent to 0.04 per cent of the total beta radioactivity. anew source of Sr99 available Apparently the Wahoo detonation made to the plankton, Fish and other organisms Eight mid-water trawls were made during the survey, one of which was lost during the recovery operation. The following organisms were collected most frequently: euphausids, lantern fish, crab larvae, miscellaneous macroplankton species. were obtained in two hauls. and Eel larvae and small squid Silversides (fish of the family Atherinidae) and hatchet fish (Sternoptychidae) were obtained only once. The gross beta radioactivity of the organisms collected in the midwater trawlis givenin Table 5. There was no detectable radioactivity in the samples collected before Wahoo (T-1 to T-4), Post-Wahoo Ss