The Division of Biology and Medicine has assigned the Applied Fisheries Laboratory the following opera- tions during and following the forthcoming test series: 1. Conduct two marine biological open sea surveys, beginning June 10 and September 1. The primary ascertain mission of these two surveys is to (a) the levels of introduced radio- activity resulting from the tests in the water, plankton, and fish, and (b) how far the activity extends westward in the North Equatorial current. — It has been recommended to the Task Force, (a) that the ship should operate from the area of highest average fallout to the westward fringe of the detectable introduced radio- activity in the water, and (b) that you or Allyn Seymour-and the ship's captain be briefed as to the location where fallout from each shot fell into the sea, prior to each survey. Each cruise should include the following: (a) (>) (c) (d) continuous water monitoring throughout the cruise. The New York Operations Office will construct and install the necessary instrumentation. water samples should be taken at 0, 25, 50, 75 and below 100 meters at selected stations. Plankton tows should be made in areas of both high and low activity. Fish should be collected wherever and whenever feasible. Preparations for undertaking these missions were made during April and May, when equipment was assembled and shipped to the Pacific Proving Ground and a schedule of staff assignments was worked out. The field group, which departed for Eniwetok early in June, included Lauren R. Donaldson, Allyn H. Seymour, Edward E. Held, Frank @. Lowman, Arthur D. Welander, Paul R. Olson, and Neal QO. Hines.