are easily fragmented during sampling and 

 handling in the laboratory. Each fragment was 

 counted as an individual (following Welch, 1948: 

 p. 287). 



Although most phytoplankton passed through 

 the mesh of the net. one alga. Halosphaera 

 viridis Schmitz, was so common that it is in- 

 cluded in all the counts. 



The averages of the number of organisms 

 per 1.000 m.'' of water and the averages of the 

 percentage composition of the plankton are tab- 

 ulated for the CHG-24 and Smith cruises in 

 tables 9. 10, and 11. By number, copepods 

 makeup about half of the catch. King and Deniond 

 (1953) and Hida and King (1955) also found that 

 copepods were the most numerous zooplankters 

 in central Pacific areas. 



Numerically as well as in percentage of total 

 volume of the catch, the upper net in the three- 

 net series nearly always produced the most zoo- 



plankton and the lower net the least. This sit- 

 uation is clearly demonstrated if the data are 

 rearranged by rank (table 12). Ostracods were 

 the only organisms that were consistently more 

 abundant in the middle stratum. Siphonophores. 

 decapod crustaceans, pteropods, gastropod lar- 

 vae, pelecypods, appendicularians, and fish eggs 

 were uniformly most plentiful in the upper stra- 

 tum and least abundant in the lower stratum. 



Decapod crustaceans were consistently more 

 abundant in the windward than in the leeward 

 area in samples from the upper net (table 13). 

 Several other taxa--the euphasiids, amphipods, 

 and appendicularians-- were also more abundant 

 in the windward area, but the difference in num- 

 bers between the two areas was not as great. 

 In the middle net. amphipods were uniformly 

 more abundant on the windward side and hetero- 

 pods were more abundant on the leeward side 

 (table 14). In the lower net foraminifers and 



Table 10. --Percentage composition and average number of organisms per 1,000 m.^ of water 

 strained by the middle net on the Smith cruises 



Item 



Cruise 



HMS-32 



HMS-34 



HMS-35 



HMS-36 



Cruise period (1956) Feb. 



Number of samples 37 



Number of day hauls 16 



Number of night hauls 17 



Number of twilight 4 



hauls 



Avg. sample vol. 15.8 



(cc./l,000 m.3) 



May 



28 



17 



7 



4 



19.5 



Aug. 

 44 

 24 

 15 

 5 



16.1 



Nov. 

 29 

 15 

 11 

 3 



9.1 



Organism 



Number per 

 1,000 m.3 



Per- 

 cent- 

 age 



Number per 

 1,000 m.3 



Per- 

 cent- 

 age 



Number per 

 1,000 m.3 



Per- 

 cent- 

 age 



Number per 

 1,000 m.3 



Per- 

 cent- 

 age 



