WILLASON ET. AL.: ZOOPLANKTON IN CALIFORNIA CURRENT 



The values of LA for Nematoscelis difficilis were 

 in the same range as those of Euphausia pacifica 

 (50 to 400), but showed a different distributional pat- 

 tern (Fig. 7). Regions of highest activity were located 

 in three small areas: adjacent to San Diego, in the 

 Santa Barbara Channel (just south of Point Concep- 

 tion), and in an area about 150 km off Monterey Bay. 

 Both males and females of N. difficilis had signifi- 

 cantly higher levels of LA in the southern portion 

 of the grid (Table 3). LA of AT. difficilis was not corre- 

 lated with chlorophyll a (Table 4). Nematoscelis dif- 

 ficilis with high LA were often found in areas with 

 very low phytoplankton biomass and vice versa. 



Euphausiid Size and Chemical 

 Composition 



Mean wet and dry weights, water content, and pro- 

 tein content (expressed as percent dry weight and 

 percent wet weight) of Euphausia pacifica and 

 Nematoscelis difficilis are presented in Table 5. 

 Female E. pacifica and both sexes oiN. difficilis had 

 significantly higher wet and dry weights in the north. 

 The water content of both euphausiid species ranged 

 from 76.5 to 81.7% and was very similar between 



species, sexes, and regions (Table 5). Protein content 

 was also very similar between species, sexes, and 

 regions. The protein values reported here (51 to 56% 

 of dry weight) are within the range of previously 

 reported values (Childress and Nygaard 1974). 



Copepod Distribution and Abundance 



Female and stage V copepodites of Calanus paci- 

 ficus were captured at all 81 stations sampled. There 

 were no significant differences between day and 

 night catches for either C. pacificus (P < 0.01, £-test). 

 For comparisons between regions, mean abundances 

 were calculated using both the log transformed and 

 nontransformed values (Table 6). The log transform- 

 ed values were used for statistical comparisons. The 

 overall abundances of females and stage V copepo- 

 dites were similar to one another in all regions (P 

 > 0.1, t-test, all cases). Both C. pacificus stages were 

 significantly more abundant in the two nearshore 

 regions (I and II) than in the two offshore regions 

 (III and IV) (Table 6). Figures 8 and 9 show that the 

 distributions of females and stage V C. pacificus 

 were patchy within regions. Copepods were particu- 

 larly abundant in the area close to and just south 

 of Point Conception. An extremely dense aggrega- 



Figure 1 —Nematoscelis difficilis lami- 

 arinase activity (LA). Expressed as 

 fig glucose per gram wet weight 

 per minute. 



Nematoscelis difficilis 



Laminarinase Activity. 



>300 



200-300 



100-199 



<100 



None 



Captured 



Point Conception 



San 

 Diego 



38 c 



36 c 



34 c 



32 ( 



124< 



122< 



120' 



118 c 



165 



