S80 EIGHTH PACIFIC SCIENCE CONGRESS 



In operation the nets were drawn obliquely through the water 

 mainly from a depth of 70 or 150 meters to the surface. 



Results. There is usually a large northern area of high plankton 

 production within the California Current (Fig. 1) and along the coast as 

 indicated by total zooplankton volume (displacement volume after re- 

 moval of large forms) per thousand cubic meters of water strained by 

 the 1-meter net. 



In Figure 2 is shown the volume distribution for cruise No. 3 which 

 provided a good geographic coverage with rather typical results. In 

 Figure 2 the average for 70-Om hauls for the whole area was 208cc/ 

 lOOOm^ of water, but for 64 northern stations the average was SOOcc/ 

 1000m3 as contrasted with an average of 75cc/1000m3 for 43 southern 

 stations. The larger northern volumes consisted mainly of the northern 

 copepods Calanus cristatus, C. tonsiis and Eucalanus bungii of both 

 northern and southern varieties. 



There is also usually a marked decrease in volume at the offshore 

 stations, particularly in the southern section. For example, in Figure 2, 

 the outer 2 to 5 stations of the seven southern lines yielded an average of 

 23.6cc/1000m3 for 26 stations. Commonly there is an increase in volumes 

 along the coast in the vicinity of central Baja California. 



For three successive years, April and May have yielded volumes 

 somewhat above the average for the year. October and November are 

 somewhat below average. The other months sampled were less con- 

 sistent though June and July catches may be relatively high and Septem- 

 ber and December low. 



Contributing to the enrichment of the plankton are certain areas 

 of upwelling along the coast where the water is characterized by lowered 

 temperatures and oxygen content and increased salinity and phosphate 

 content. This upwelling is associated with periods of northwest winds, 

 usually occurring during spring and summer. The coastal areas most 

 affected from north to south are Cape Mendocino, Soberanes Point, 

 Point Conception and the region off central Baja California. 



The coastal area is devisable also on a qualitative basis which out- 

 lines more or less clearly adjoining northern and southern pelagic faunal 

 areas. These are separated roughly by the 13°-14°C isotherms for the 

 30-meter depth. In spring the isotherms cut obliquely from offshore at 

 35-40' North latitude towards the coast of Baja California at 30 °N 



(P^g- 2). 



Conspicuous in the plankton of the northern area are especially 

 the copepods Calanus cristatus, C. tonsus, and Eucalanus bungii. Can- 

 dacia columbiae, Epilabidocera aniphitrites, while rare, are indicative 

 of the northern fauna. Other planktonic crustacean groups with species 



