Variations from the calculated depths for the 

 single-net hauls were considered to be minor; 

 therefore, corrections were not applied. Depths 

 given in the tables in the appendix for the single- 

 net hauls are to the nearest 5 m. 



COMPREHENSIVE SERIES 



The comprehensive series was an investiga- 

 tion of vertical, horizontal, and seasonal fluc- 

 tuations in abundance of zooplankton throughout 

 the waters adjacent to Oahu. 



Forty-eight stations were established initially 

 (fig. 1), but their spacing proved to be unsatis- 

 factory during CHG-24, the first cruise. For 

 subsequent cruises, the stations were reduced 

 from 48 to 45 and were spaced more evenly 

 (fig. 2). The stations were visited every 3 

 months to obtain a measure of seasonal varia- 

 tion. At each station, three nets were towed 

 simultaneously at three levels, an open net at 

 to 60 m., and closing nets at 70 to 130 m. and at 

 140 to 200 m. to determine vertical differences. 



This procedure in' which three nets were used 

 was followed exactly on HMS-32, 34, and 35, 

 but not on the other two cruises of the compre- 

 hensive series. On CHG-24 (before the closing 

 nets were available), all hauls were made with 

 single open nets; alternate tows were made be- 

 tween the surface and the top of the thermocline 

 (at odd-numbered stations), and between the 

 surface and 200 m. (at even-numbered stations). 

 On HMS-36, owing to the loss of equipment at 

 the first sampling station, only two nets were 



used: an open net at to 60 m. and a closing 

 net at 70 to 130 m. (here considered the middle 

 net of HMS-36). 



Figure 1. --Stations for collecting zooplankton 

 on CHG-24. 



Figure 2. --Stat ions for collecting zooplank- 

 ton for comprehensive series. The division 

 between windward and leeward stations is 

 shown by a dotted line. 



Vertical Distribution 



The catches made on the Hugh M. Smith 

 cruises yielded information on vertical and diel 

 variations in the distribution of zooplankton. 

 Since the volumes of catches in the middle and 

 lower nets of this series did not show a signifi- 

 cant regression on the sine curve, they were 

 not adjusted for diel variation. The samples 

 from these three hauls were classified as day, 

 night, or twilight,^' according to the time of 

 hauling, and unadjusted volumes were averaged 

 for the samples from each time group (table 4). 



The catch of zooplankton decreased with in- 

 creasing depth regardless of the time of day. 

 The single discrepancy was for HMS-34, when 

 the average catch in the middle net was greater 

 than that in the upper net during the day but 

 about equal to it at night. 



The quantities of zooplankton in the different 

 strata of water during different light periods 

 were compared on the basis of pooled data from 

 the four cruises (table 5). In night hauls the 

 middle stratum yielded an average of about 2.9 

 times, and the upper stratum about 4.4 times, 



3/ 



— The hours of each time interval were deter- 

 mined from the American Nautical Almanac. 



