Acknowledgements Operation Troll was conceived by Mr. Merril Eisenbud, Director of the Health and Safety Laboratory. The basic idea was confirmed and elaborated by Dr. Allyn C. Vine of Woods Hole Oceanographic Institution, and the project presented to the Division of Biology and Medicine for approval. The general concepts of the operation were discussed at an ad hoc meeting in Washington on January 12, 1955, The following were present: Dr. A.C. Vine, Woods Hole Oceanographic Institution Dr. J. Isaacs, Scripps Institution of Oceanography Dr. T. Folsom, Scripps Institution of Oceanography Mr.F. Jennings, Scripps Institution of Oceanography Dr. J. Smith, Office of Naval Research Mr. J. Kane, Office of Naval Research Mr.H.D. LeVine, US Atomic Energy Commission. Drs. Vine and Isaacs were of the opinion that there was a probability that the radioactive water was still contained in the currents and, although reduced in intensity, might well be on the way to Japan. They also expressed the belief that there must be a concentration of activity by the plankton and an additional concentration in the tuna which feed on the plankton in this stream. For this reason, they recommended that the investigation proceed. The detailed planning was worked out among Mr. James W.Smithand Mr. John J. Kane of the Office of Naval Research, Dr. Warren S. Wooster of the Scripps Institution of Oceanography, Mr. Howard Brown and Dr. Willis R. Boss of Biology and Medicine, and Mr. Eisenbud and Dr. Harley of HASL. , Work at sea was carried out by the following personnel, under the leadership of Dr. Harley: New York Operations Office, US Atomic Energy Commission John H. Harley, Chief, Analytical Branch, HASL Robert S. Morse, Chemist, HASL Rudolf Anker, Electronics Technician, HASL