This report contains the biological and oceanographic data collected during five cruises in the central North Pacific by the Bureau of Commercial Fisheries research vessels Hugh M. Smith and Charles H. Gilbert. Participating scientists collected oceanographic and biological data designed to determine the distribution of surface water types and the associated biota, particularly skipjack tuna Katsuwonus pelamis (Linnaeus). The area investigated was bewteen longitudes 155° and 170° W, at latitudes 15° to 26° N.