REPORT ON OCEANOGRAPHY 5 



and antarctic and it sinks by day and rises at night. This deep plank- 

 ton layer contains many sizable forms of euphausiids and small fishes, 

 and it is suspected that some of the tuna feed there. If the plankton 

 rise above the thermocline into the warm layers, it would be invading 

 the habitat of the tuna, and they could feed on it. If the plankton 

 rose only to the thermocline, but not through it, it is possible that the 

 tuna would find it. They could make forays into the colder waters, 

 and return to the upper warm waters between feedings. But if the 

 plankton is always well below the thermocline it may be doubtful if 

 the tuna would find it, 



Oceanographic data should designate the areas where the deep 

 plankton rise to or through the thermocline. Echo sounders reveal the 

 depths at which the plankton layer exists and also indicate the possible 

 presence of tuna. New types of gear for deep fishing need to be devel- 

 oped or some method devised for luring the fish within the range of 

 existing gear. 



This is the oceanographic method. To learn the requirements of 

 the fish; to determine when, where, and how these occur; and then to 

 seek the fish in the most likely places, at most suitable times, and where 

 necessary develop methods of detection and fishing. The last steps are 

 simple, when the biology and oceanography are complete, as shoAvn by 

 the investigations of the Conseil Permanent pour I'Exploration de la 

 Mer, in the North Sea. 



This reasoning would be sufficient if extensive knowledge of the 

 plankton were known as well as many details concerning the properties 

 and characteristics of the waters. For most of the Pacific this knowl- 

 edge is very incomplete. One is confronted with the threefold task of 

 exploring the ocean for tuna, solving the living habits of plankton and 

 charting the properties and characteristics of the water masses. 



During the span of the Pacific Science Association, since 1924, the 

 Pacific Ocean has been explored. Many oceanographic expeditions have 

 defined the water masses, charted the currents, recognized the properties 

 of the water, and studied the fish and the plankton. The major water 

 masses, the principal currents, and the generally productive and unpro- 

 ductive areas are known. However, detailed knowledge is very meager. 

 The cycles of temperature, salinity, and productivity, the variations in 

 currents, the migration routes and fluctuations of the fisheries are the 

 present concern. 



Research in oceanography is expensive. It requires expensive ships, 

 expensive equipment, highly-trained personnel and a large operational 

 investment. The specialized agencies of the United Nations have real- 

 ized this and the Food and Agriculture Organization has during the 

 past five years sponsored the Indo-Pacific Fisheries Council, an associa- 



