SARDINE LARVAE 

 GRIDS I - V 



I - 6 

 7-60 

 61 - 600 

 over 600 



Figure 3. Sardine larvae: distribution and relative abundance on Grids I - V, April 18-23, 1952. 



and day stations, omitting the ones occupied 

 at or one-half hour before and after sunset 

 (Ahlstrom, 1954b). Final ratios on the grids 

 showed that 1.88 times as many Leuroglossus 

 stilbius larvae and 2.66 times as many 

 Lampanyctus mexicanus larvae were collected 

 at night than in the day (table 12). Collections 

 on drogue and anchor stations were either day 

 or night; none were omitted. Five-day ratios of 

 Leuroglossus stilbius larvae per haul showed 

 2.38 and 2.22 times as many collected at 

 night as in the day on the drogue and anchor 

 stations respectively (table 13). The 5-day 

 ratios for Lampanyctus mexicanus larvae per 

 haul on the drogue and anchor stations re- 

 spectively showed 1.82 and 1.44 times as many 

 collected at night as in the day (table 14). 



PLANKTON VOLUMES 



The plankton volumes reported in table 1 

 are based on milliters of "wet" plankton per 

 1,000 cubic meters of water strained. The 



procedures for measuring plankton were the 

 same as those described in the reports on 

 the annual collections by this laboratory al- 

 ready referred to above. 



Relative concentrations of plankton volumes 

 are depicted for the grids by light and heavy 

 shading (fig. 6). The categories of these vol- 

 umes are: (1) "very light", 33 ml, or less; 

 (2) "light", 33-100 ml.; (3) "moderate", 100- 

 300 ml,; (4) "heavy", 300-900 ml,; and (5) "very 

 heavy", more than 900 ml. Histograms are used 

 to show the plankton volumes of successive 

 samples taken at drogue and anchor stations 

 (fig. 7). 



Plankton volumes in the grids were generally 

 in the light category. When very light concen- 

 trations occurred they were usually in the 

 eastern half of each day's pattern. Greater 

 concentrations, in moderate to very heavy 

 categories, usually occurred in the western 

 sections. The exception was the fifth day when 

 only two stations showed moderate plankton 



21 



