WILLASON ET AL.: ZOOPLANKTON IN CALIFORNIA CURRENT 



Table 2— Mean surface water temperature and mean surface chlorophyll a. Chlorophyll 

 a expressed as mg/m 3 . The numbers in parentheses are one standard deviation. 



indicates value(s) significantly different from those of other regions (P < 0.05, t-test). 



Surface Temperature (°C) 



9.0- 9.9 



10.0-10.9 

 11.0-11.9 

 12.0-12.9 

 13.0-13.9 

 14.0-14.9 

 15.0-16.0 



Figure 2 — Surface water temperatures 



(°C) along the California coast. L 



124 c 



122' 



120 c 



118 c 



this region two areas of very high chlorophyll a (up 

 to 14.7 mg/m 3 ) were found: near Point Conception 

 and just south of San Francisco Bay. These areas 

 were located just south of the areas of coldest sur- 

 face waters. 



Euphausiid Distribution and Abundance 



Euphausia pacifica adults were captured at 43 of 

 the 81 stations sampled and Nematoscelis difficilis 

 adults were captured at 38 stations. As there was 

 no significant difference between numbers of males 

 and females captured of either species (P > 0.3, 

 Wilcoxon test), the abundances shown in Figures 4 

 and 5 represent the sum of both sexes. Both the 

 number of specimens ofN. difficilis captured at each 



station (P < 0.01, t-test) and the proportion of sta- 

 tions where individuals were caught (P < 0.01, x 2 

 test) were greater at night. For E. pacifica, there 

 were no significant day-night differences in the num- 

 bers of animals captured (P > 0.2, £-test), however, 

 like N. difficilis, the proportion of stations where 

 individuals were captured was greater at night (P 

 < 0.05, x 2 test). The day-night differences may 

 represent net avoidance by euphausiids or under- 

 sampling during the day because of vertical migra- 

 tion. Thus, the data presented in Figures 4 and 5 

 represent general trends and are intended to show 

 relative differences between areas. Because euphau- 

 siids were captured at only about one half of the sta- 

 tions, statistical comparisons were made only 

 between the north and south (i.e, nearshore and 



161 



