Zooplankton Volumes off the Pacific Coast, 1952 



This report contains a record of the volumes of zooplankton taken on 

 the survey cruises of the California Cooperative Sardine Eesearch Program 

 during 1952, along with information on the plankton hauls. The survey 

 cruises, made monthly except during December, were numbered 33 through 43» 

 Participating vessels included the CREST, E.W. SCRIPPS, HORIZON, PAOLINA T. 

 and S.F. BALED of the Scripps Institution of Oceanography, the YELLOWFIN 

 of the California Department of Fish and Game, and the BLACK DOUGLAS of 

 the U. S. Fish and Wildlife Service. Two to four vessels took part in 

 each cruise. 



The plankton samples are used in studying the distribution and abun- 

 dance of the eggs and larvae of the pilchard or sardine (S ardinops caerulea ). 

 and also in studying the productivity of pilchard spawning areas. The 

 former problem is being investigated by the U. S. Fish and Wildlife Ser- 

 vice, the latter by the Scripps Institution of Oceanography. Both inves- 

 tigations are directed toward determining the factors affecting the success 

 or failure (good or poor survival) of year classes of pilchard. 



The plankton hauls were made obliquely from approximately 140 meters 

 deep (200 meters of wire out at greatest depth) to the surface. The hauls 

 were made at a vessel speed of 1.5 to 2 knots. In taking a haul, the net 

 was lowered to a depth of approximately 140 meters in about 4 minutes and 

 then brought upward at the rate of 14 meters per minute (20 meters of wire 

 retrieved). 



The same type of plankton net has been employed since 1949. The net 

 measures 1.0 meter in diameter at the mouth, by approximately 5 meters in 

 length. The anterior section of the net, approximately a meter in length, 

 is cylindrical; the longer posterior section conical. A cod-end bag is 

 attached to the end of the net by a bronze coupling device. The body of 

 the net is constructed of No. 30xxx grit gauze (a rugged grade of silk 

 bolting cloth), the posterior 40 cms. of the cone and the cod-end bag of 

 No. 5&xxx grit gauze. 



Each plankton net is provided with an Atlas-type current meter, held 

 rigidly in the center of the mouth opening. The current meter consists 

 of a rotator and a revolution counter housed in a cylindrical casing. 

 Current meters were calibrated before and after each cruise on which they 

 were used. 



