suggest, confirm, or deny hypotheses about re- 

 lationships of biological properties to each 

 other and to the physical environnnent. The 

 boundaries of the eastern tropical Pacific 

 Ocean are defined as lat. 30° N., long. 130° 

 W., lat. 40° S., and the American coast. 



Wooster and Cromwell (1958) called the 

 eastern tropical Pacific "almost completely 

 unknown from a scientific point of view." They 

 pointed out that the first comprehensive ocea- 

 nographic survey covering a large part of the 

 region was not made until 1952. Biological 

 oceanography (zooplankton only) formed part 

 of this 1952 survey ("Shell back" expedition, 

 see table 1). In the same year the Galathea 

 measured primary productivity at a few sta- 

 tions. The biological oceanography of the 

 region at large may therefore be said to date 

 from 1952, although significant work of this 

 kind was done on one much earlier expedition 

 to a particular area [the 1931 cruise of the 

 William Scoresby in the Peru Current (Gun- 

 ther, 1936)]. The first comprehensive expedi- 

 tion in which biological oceanography played a 

 large and diversified role was "Eastropic" in 

 1955. In 1955-61 activity in this field was con- 

 siderable (table 1). 



Much of the impetus for this biological 

 oceanography was generated by biologists who 

 were concerned with the ecology, especially 

 trophic relationships, of commercially valu- 

 able pelagic fishes of the eastern tropical 

 Pacific, These fishes include: yellowfin tuna, 

 Thunnus albacares ; bigeye tuna, Thunnus 

 obesus; skipjack tuna, Euthynnus pelamis ; and 

 the Central American anchoveta, Cetengraulis 

 mysticetus , which was formerly important as 

 a tuna baitfish. Thus the Bureau of Commercial 

 Fisheries and the Inter -American Tropical 

 Tuna Commission played a major role in de- 

 veloping biological oceanography in the eastern 

 tropical Pacific; from 1957 onwards, most of 

 the Bureau's work in this field was done under 

 contract by the Scripps Tuna Oceanography 

 Research (STOR) Program of the Institute of 

 Marine Resources, Scripps Institution of Ocea- 

 nography, University of California. The con- 

 centration of most of this activity on the epi- 

 pelagic community of organisms reflected the 

 interest in the fishes mentioned above. Prac- 

 tically no work has been done on the benthic 

 communities. 



Southern Californian institutions (Scripps 

 Institution of Oceanography, Inter- American 

 Tropical Tuna Commission, and California 

 Department of Fish and Game) provided the 

 staff and equipment for most of the biological- 

 oceanographic expeditions from 1952 onwards, 

 including (in part) two foreign expeditions, 

 those of the Chilean Esmeralda in 1962 and the 

 Japanese Shoyo Maru in 1963-64. The arrange- 

 ment resulted in reasonable standardization of 

 methods in biological oceanography on these 

 cruises. Data from certain other expeditions in 

 or after 1952 are generally not comparable 



methodologically with those mentioned above 

 and are not nearly as plentiful (for the eastern 

 tropical Pacific) either; therefore they have 

 not been used in this paper. These expeditions 

 are: four cruises of the BCF (Bureau of Com- 

 mercial Fisheries) Biological Laboratory at 

 Honolulu ( Hugh M. Smith and Charles H. 

 Gilbert ) including the part of "Eastropic" ex- 

 pedition which was based on Honolulu; the 

 Danish Galathea cruise of 1952; a cruise by 

 Yale University in 1953; and cruise 29 of the 

 Soviet Vityaz in 1958-59. All operations are 

 listed in table 1 and are henceforth referred 

 to by their numbers in that table. 



Table 1 does not include some long series 

 of biological oceanographic cruises made off 

 Baja California by CalCOFI (California Co- 

 operative Oceanic Fisheries Investigations), 

 and in the Gulf of Panama and the sea off 

 Ecuador by the Inter- American Tropical Tuna 

 Commission, although some of the data and 

 conclusions are mentioned later. Nor does it 

 include cruises made by South American 

 organizations (e.g., Institute del Mar del Peru) 

 in waters close to their own coasts because I 

 have seen no tabulated data from them. 



A few errors in published values of chloro- 

 phyll a and primary productivity from opera- 

 tion 16 have been discovered and are cor- 

 rected in the Appendix. 



MATERIAL AND METHODS 



The principal kinds of biological properties 

 measured have been: standing crop of chloro- 

 phyll a, primary productivity (rate of primary 

 production), standing crop of zooplankton, 

 and standing crop of micronekton. Standing 

 crop of phytoplankton has not often been re- 

 ported in terms of biomass or numbe r of cells. 



The methods of making these measurements 

 were reasonably comparable, and the work was 

 done to a large extent by the same persons 

 using the same equipment, in all operations 

 except those marked with an asterisk in table 

 1. The methods used in the operations included 

 here may be summarized as follows. 



Chlorophyll a 



The well-known method, which involves 

 filtration, extraction with acetone, and spec- 

 trophotometric measurement of optical density 

 of the extract, was used. Full details were 

 given by Holmes et al. (1957), Holmes and 

 Blackburn (I960), Forsbergh and Joseph ( 1964), 

 and Holmes (MS.^). The concentrations, 

 in milligrams per cubic meter of water .fil- 

 tered, were calculated from the equation of 



' Holmes, Robert W. A contribution to the physical, 

 chemical, and biological oceanography of the northeastern 

 tropical Pacific. (Scripps Institution of Oceanography, 

 University of California, 1964). 



