ZOOPLANKTON VOLUMES OFF 

 THE PACIFIC COAST, 1958 



by 



James R. Thrailkill 



Since 1949, information on zoo- 

 plankton volumes obtained on CalCOFI 

 cruises has been published annually. 

 Eight papers have appeared in this 

 series, six published under the author- 

 ship of "Staff of the South Pacific 

 Fishery Investigations" and tvi^o (1957 

 and 1959) under the authorship of 

 James R. Thrailkill. Thrailkill (1956) 

 illustrated monthly plankton distribu- 

 tions for 1949 through 1955. Distribu- 

 tion charts have been included in sub- 

 sequent reports. 



The investigation of zooplankton 

 volumes off the Pacific coast is a 

 part of the California Cooperative Oce- 

 anic Fisheries Investigations (Cal- 

 COFI). This research is sponsored by 

 the Marine Research Committee and 

 carried out cooperatively by the Scripps 

 Institution of Oceanography of the Uni- 

 versity of California, the Pelagic Fish 

 Investigations of the California De- 

 partment of Fish and Game, the Cali- 

 fornia Academy of Sciences, the 

 Hopkins Marine Station of Stanford 

 University, and the U.S. Bureau of 

 Commercial Fisheries Biological Lab- 

 oratory, La JoUa, California. The 

 plankton collections are obtained on 

 oceanographic-b i o 1 o g i c a 1 survey 

 cruises made on vessels operated by 



Note,- -James R. Thrailkill, Fishery Research 

 Biologist, Bureau of Commercial Fisheries, U. S. Fish 

 and Wildlife Service, La Jolla, California. 



Scripps Institution of Oceanography 

 and the U.S. Bureau of Commercial 

 Fisheries, Biological Laboratory, La 

 Jolla. 



The plankton samples are used 

 by the Bureau of Commercial Fish- 

 eries in studying the early life history 

 of commercially important, or poten- 

 tially important fishes, including their 

 distribution, abundance and rate of 

 survival. Scripps Institution of Ocea- 

 nography also makes use of the samples 

 in studies of productivity and zoo- 

 geography. 



Vessels participating in CalCOFI 

 cruises of 1958 (table 1) included five 

 operated by the Scripps Institution of 

 Oceanography and one, the Black 

 Douglas, operated by the Bureau of 

 Commercial Fisheries. The stations 

 occupied during 1958 are shown in 

 fig. 1. A chronological list of the 

 survey cruises made in 1958, including 

 the area covered and the number of 

 stations occupied on each, is given in 

 table 2. 



The plankton collecting equipment 

 and the procedures employed in taking 

 hauls were standard on all vessels. 

 The nets, constructed of No. 30xxx 

 grit gauze (a heavy-duty grade of 

 silk bolting cloth) were 1 meter in 

 diameter at the mouth and about 5 

 meters in length. All plankton hauls 

 w^ere taken obliquely from a depth 



