PRELIMINARY REPORT ON EXPEDITION EASTROPIC 



By 



Joseph E. King, Thomas S. Austin, and Maxwell S. Doty 



The EASTROPIC Expedition was a 

 cooperative oceanographic survey of the central 

 and eastern tropical Pacific conducted during 

 the period September -December 1955. Five re- 

 search vessels took part in the survey, r e p r e - 

 senting five agencies: Scripps Institution of 

 Oceanography, Inter -American Tropical Tuna 

 Commission, California Department of Fish 

 and Game, Pacific Oceanic Fishery Investiga- 

 tions (POFI) of the U. S. Fish and Wildlife 

 Service, and the Peruvian Navy. 



Personnel of the Scripps Institution of 

 Oceanography and the Inter -American Tropical 

 Tuna Commission aboard the Scripps' vessels 

 Spencer F. Baird and Horizon operated south- 

 ward from San Diego as far as northern Peru 

 and from the Central American Coast westward 

 to about 120°W. longitude. These vessels 

 studied the currents and productivity of the 

 Equatorial Countercurrent, the Equatorial 

 Undercurrent, and the region along the northern 

 boundary of the Peru Current between Ecuador 

 and the Galapagos Islands. The Peruvian 

 vessel B. S. P. Bondy occupied hydrographic 

 stations and made bathythermograph observa- 

 tions along the latter current boundary and then 

 worked southward into the Peru Current itself. 



The California Department of Fish and Game 

 vessel N. B. Scofield conducted longline fishing 

 in all three current systems. 



As POFI's participation in EASTROPIC, 

 the Hugh M. Smith (cruise 31) completed an 

 86 -day, 14,000-mile cruise (fig. 1), obtaining 

 information on east-west gradients in tempera- 

 ture, salinity, phosphate, zooplankton, and 

 forage fish abundance along the northern bound- 

 ary of the Equatorial Countercurrent and along 

 the Equator between IICW. and 156*W. longi- 

 tude. In collaboration with the University of 

 Hawaii, carbon fixation and chlorophyll mea- 

 surements were made on the westbound leg of 

 the cruise. A survey of tuna baitfish was con- 

 ducted in the Marquesas Islands. 



The purpose of this report is to list the 

 results -- without analysis -- obtained on the 

 cruise of the Hugh M. Smith , in order to make 

 these data available, without further delay, for 

 the joint benefit and use of all collaborating 

 scientists and other agencies interested in the 

 oceanography of the central and eastern Pacific. 

 More definitive reports will follow. 



Figure 1. --Track of the Hugh M. Smith (cruise 31) on the EASTROPIC 

 Expedition, September 23 to December 17, 1955. 



