During the last two decades [1950s-1960s] a number of expeditions have worked in the eastern tropical Pacific Ocean, so that the general features of its circulation and biology have been described. (References to such investigations are to be found in the two reports of the Eastern Pacific Oceanic Conference - EPOC, cited below). However, the accumulated observations are too poorly arranged in time and space to describe, in an adequate fashion, the monthly or seasonal variation in the distribution of physical or biological properties. Large-scale changes in the atmospheric circulation clearly lead to changes in mass transport within major components of the circulation, as well as causing variation in the intensity of vertical motion on the equator and along the continental margin. In order to understand and to predict the nature of such variation it was evident from the data of previous studies in the eastern tropical Pacific Ocean that a more solid data base for modeling circulation and biotic production in this region was necessary.
          Many of the members of the EPOC are engaged in research in the eastern tropical Pacific, and a proposal for a detailed and comprehensive study of the upper ocean in this area originated in 1960 at the Seventh Annual Meeting of EPOC. The Conference appointed a Committee, chaired by Gerald V. Howard of the Bureau of Commercial Fisheries (BCF, now National Marine Fisheries Service) to consider the desirability, feasibility, and possible scope of a cooperative program of oceanic survey and research in the eastern tropical Pacific Ocean. This Committee reported the results of its study to the Eighth EPOC, held in September 1961, and published these as the Report of EPOC on a Cooperative Program of Study of the Eastern Tropical Pacific Ocean.
          The recommendations called for a $20-million oceanography program to begin in 1963 and run for a period of 8 years to encompass general survey work and special research in meteorology; physical, chemical, and biological oceanography (including fisheries); geology; and geophysics. It noted that such a program would not only greatly advance the marine sciences and provide opportunities for significant new understanding of the ocean, but would also be of value in providing the scientific basis for increasing the harvest of the fisheries of the region, forecasting weather, and improving shipping and navigation. It recommended that the U.S. Interagency Committee on Oceanography (ICO) and the individual agencies of the government should begin planning for support of the program. It also recommended that international participation and aid should be sought through appropriate international agencies and from Latin American institutions with oceanographic capabilities. The program then received the approval of the Intergovernmental Oceanographic Commission at its meeting in Paris in September 1961.
          However, for various reasons, 4 years elapsed and little progress was made before implementation of the EPOC plan. Between the fall of 1963 and the spring of 1964, a group of scientists from several agencies engaged in oceanography in the eastern Pacific met to consider the EPOC program in the light of developments, or lack thereof, towards its implementation during the intervening years. This ad hoc group agreed that two major factors were deterrents to the program. The funding agencies appeared to consider the proposed survey and research too costly, and some parts of the program had not attracted the scientists who would be required to carry them out.
          The ad hoc group decided to revise and trim the EPOC program as originally recommended in the hope of overcoming major obstacles apparently blocking its implementation. It took into consideration recent developments, especially in the fisheries of the eastern tropical Pacific and the present and potential manpower and facilities of the scientific community. It concluded that the geological-geophysical portion could be deleted because it dealt with time-independent properties not closely related to the rest of the program, and that the detailed meteorological program could be reduced. Also, it was decided that the research cruises and special research projects could be omitted from the basic plan since these would follow as people recognized their possibilities and importance. What remained of the original proposal, then, was the hard core of the field survey program for physical, chemical, and biological oceanography and essentials of the meteorological program, although even these efforts were reduced to coincide with reductions in research ship time. While trimming the overall oceanographic program as originally conceived, the ad hoc group recognized a need to include fishery surveys in the plan to insure that the fishing industries would obtain maximum benefit from the proposed work in descriptive oceanography. The revised program was now labeled EASTROPAC A Cooperative Effort Towards Understanding of the Oceanography of the Eastern Tropical Pacific Ocean.
          The ad hoc group prepared estimates of the total funds that would be required to launch the field operations associated with EASTROPAC, process the data collected, analyze the data, and prepare reports on the results. In making the estimates, the group took into account the existing capabilities - available scientific personnel and oceanographic programs underway in the laboratories already engaged in studies of the eastern tropical Pacific Ocean - that were available for the EASTROPAC expeditions. Thus, the major share of the budget prepared was for the support of ship operations and unmanned buoys.
          EASTROPAC finally became a reality with the first cruise scheduled for February-March 1967. The investigations were to be coordinated by the Bureau of Commercial Fisheries through its laboratory in La Jolla, and in June 1966 a Coordinator, Dr. Warren S. Wooster, Scripps Institution of Oceanography (SIO), was appointed; in May 1967, Dr. Alan R. Longhurst, then of SIO, replaced Dr. Wooster. As his first task, Dr. Wooster enlisted the support of various Federal agencies and scientific institutions in providing ships and personnel. Mexico and a number of South American countries were also asked to participate because of the importance of these expeditions to Latin American fisheries.
          By the time the first expedition was due to sail, an impressive number of agencies had pledged their support in one way or another; these included international and foreign organizations as well as United States universities and Federal agencies.

The organizations involved in EASTROPAC, and the nature of their involvement, were as follows:

  • Inter-American Tropical Tuna Commission (IATTC). La Jolla, California. Participation of biological and physical oceanographers and technicians aboard U.S. and Latin American research vessels. Performed analysis of meteorological data and sorting of zooplankton samples under contract to Bureau of Commercial Fisheries. Provided computer programming services and assistance in reduction and analysis of some Latin American data.

  • Chile - Instituto Hidrográfico de la Armada. Organization and manning of research cruises off Chile on Chilean research vessel Yelcho and through tropical area by Esmeralda.
  • Ecuador - Instituto National de Pesca. Organization and manning (with IATTC) of research cruises off Ecuador with Ecuadorian research vessel Huayaipe.
  • Peru - Instituto del Mar. Organization and manning of research cruises off Peru with Peruvian research vessel Unanue.
  • Mexico - Dirección General de Pesca e Industrial Conexas. Organization and manning (with IATTC) of research cruises off Mexico with Mexican vessels Yolanda and Tuxpan and a chartered U. S. vessel, Defiance (with IATTC and the U. S. Bureau of Sport Fisheries and Wildlife).

United States:
  • U.S. Coast Guard. Provision of USCG research vessel Rockaway for three major cruises off Central America and partial provision of her scientific party, the rest supplied by other agencies. Provided financial support for atlas publication.
  • U. S. Department of Commerce (ESSA). Provision on some of the major cruises of Weather Bureau personnel and equipment for taking surface and upper air observations. Designated one leg of the inaugural voyage of U.S. Coast and Geodetic Survey Ship Oceanographer for EASTROPAC participation.
  • U. S. Department of the Navy (ONR). Provision of funding in support of some of the university research vessels participating and of processing and analysis of data obtained. (NAVOCEANO). Designated a portion of a research cruise of the USNS Charles H. Davis for EASTROPAC participation.
  • National Oceanographic Data Center (NODC). Consultation and cooperation concerning standardization of observational and data-recording techniques. Sent one oceanographer to La Jolla for 6 months to assist in processing of physical oceanographic data. Provided financial support for atlas publication.
  • National Science Foundation (NSF). Funds in support of some university personnel and research ships.
  • Smithsonian Institution. Provision of ornithologists trained in seabird and fish-school observations for most of the major cruises.
  • Stanford University. Supplied data from research vessel Te Vega which operated concurrently in the survey area.
  • University of California (Scripps Institution of Oceanography). Provision of research vessels Thomas Washington and Argo, and partial provision of their scientific parties. Provision of two instrumented buoys to be moored in the survey area. Assistance subsequent to the expeditions in reduction and analysis of data.
  • Texas A & M University. Provision of research vessel Alaminos and partial provision of her scientific party. Supply of meteorological instruments for other vessels.
  • U. S. Department of the Interior (Bureau of Commercial Fisheries). Provision of coordination unit at La Jolla, of research vessels David Starr Jordan and Undaunted and their scientific parties; post-expedition reduction and analysis of data. Provided financial support for atlas publication.

          The EASTROPAC expeditions were unique in their scope and in the degree of coordinated planning of the cruises. In size of area and number of observations, EASTROPAC was comparable with such major international efforts as the International Indian Ocean Expedition, yet, unlike IIOE, all participating ships worked tracks designated prior to the expeditions to survey comprehensively the designated area in space and time; all participating ships undertook to perform a standard and basic suite of physical and biological observations, using standardized gear and conforming to standards laid down by the EASTROPAC Manual of Observations (Staff EASTROPAC, 1967) issued before the first cruise and modified only very slightly during the 14 months the expeditions occupied. Such routine observations formed a very large part of the effort of each participating ship and other scientific activities were performed only on a "not to interfere" basis.
          The expeditions were extremely fortunate in the small number of medical emergencies and ship breakdowns which disrupted planned observational patterns, and only minor modifications had to be made to planned cruise tracks. This was due in no small part to the enthusiasm of the individual participants aboard the expedition ships, whose dedication to the idea behind the series of expeditions must be recognized and acknowledged by those involved in its planning.
          It was decided by a meeting of the EASTROPAC Coordinating Committee in April 1968, that the data derived from the expeditions were so numerous as to render classical data reports impractical, and it was decided that all data should be archived on magnetic tape at the National Oceanographic Data Center after they had been used for production of a comprehensive atlas of the physical and biological results of the expeditions. It was also decided, in view of the volume of the data and the consequent number of sheets in the atlas, the preliminary data processing and chart analyses would be performed entirely by computer. Therefore only minimum hand computation and limited drafting were needed in this atlas. Only in this way could it have been produced in the short time available and as economically as it has been; the presentation may not be as aesthetically pleasing as in more classical atlases but it is hoped that our charts and sections will be equally as useful as hand-drawn ones.
          In accepting the role of coordinating agency for EASTROPAC, the Bureau of Commercial Fisheries recognized that the expeditions were a necessary preliminary to fishery development in the eastern tropical Pacific Ocean to the west of the present-day tuna fisheries. A second-phase operation was visualized after data reduction, analysis, and presentation were completed for the original series of EASTROPAC expeditions. This second phase would consist of (1) stock assessment of oceanic tunas and determination of their availability to a fishery, in areas and at seasons indicted by analysis of EASTROPAC data; (2) further investigations of phenomena, physical or biological, demonstrated by the initial data to be interesting yet improperly understood; and (3) a determination from the initial expedition data, what way these data and later monitoring operations (surface ships, buoys, or remote sensors) might be used to develop fisheries advisory services for the tropical tuna fleet.
          At the time of writing, in early 1970, the Bureau of Commercial Fisheries is moving towards these second-phase objectives.

Alan R. Longhurst, EASTROPAC Coordinator