Zooplankton Volumes off the Pacific Coastj 19^3 



This report, the fourth in a series, contains a record of the volumes 

 of zooplankton collected on the survey cruises of the California Cooperative 

 Oceanic Fisheries Investigations off the Pacific coast of California and 

 3a ja California. Regular survey cruises viere nsde at monthly intervals, 

 except in September and November. An area off southern California (station 

 lines 83-87) was occupied more frequently, including cruises in September 

 and November. The vessels participating in cruises during 19^3 included the 

 CREST, E, W. SCRIPPS, HORIZON, PACLINA To and Sc F„ BAIRD, of the Scripps 

 Institution of Oceanography, and the YELLOViTFU'J of the California Department 

 of Fish and Game. 



The plankton samples are used in studying the early life histories 

 (particularly the distribution and abundance of spawning and the rate of 

 larval survival) of the sardine and other commercially important or poten- 

 tially important fishes, and also in studying the productivity of sardine 

 spavming areas. The former problem is being investigated by the South 

 Pacific Fishery Investigations of the United States Fish and Wildlife Ser- 

 vice, the latter by the Scripps Institution of Oceanography of the Univer- 

 slty of California. 



The nets used on these cruises were the same as those used on all 

 cruises since 19U9. They were made of No. 30xxx grit gauze Can extra-strong 

 silk bolting cloth), conical in shape, with a 1-meter mouth opening, and 

 about 5 meters long. The last kO cms. of the cone, and the cod-end bags 

 were made of No. 56xxx silk grit gauze. 



The procedure for taking net tows was suandard for all cruises. Each 

 haul was made with 200 meters of wire out (approximately lUO meters deep) 

 v/herever depth of water permitted. The estimated depth of each haul is 

 given in column 8 of the following tables . 



The volume of plankton measured for each station is the "wet" volume. 

 Each sample was filtered from its preserving fluid and its volume determined 

 by displacement. The volumes listed in the following tables are (1) the 

 total wet volumes standardized to the amount in 1000 cubic meters of water 

 strained (column 9), and (2) the volume of smaller organisms after the 

 removal of larger ones such as jellies, fish, larger mollusca, crustaceans 

 and squid (column 10). 



A different system of numbering cruises than that used in preceding 

 reports, is now in effect. The cruise number is composed of four digits, 

 the first two of which refer to the year, the other tvio to the month. Thus, 

 Cruise 5301 is the January cruise of 1953, Cruise 5310 the October cruise of 

 1953 • Formerly, consecutive numbers were given to cruises of the California 

 Cooperative Fisheries Investigations. If the earlier system were followed, 

 the 1953 cruises ivould be numbered UU (January) through 55 (December). 



