SUMMARY AND CONCLUSIONS 



At 30 stations in a series along 150 W. longitude from 12 N. to 7 S. latitude, 68 samples 

 were obtained at three depths--the surface, the level of the 70 F. isotherm, and at approxi- 

 mately 200 meters--by means of horizontal closing-net hauls with Clarke-Bumpus samplers. 



According to an analysis of variance, for surface hauls the volumes of the night samples 

 were significantly greater (P < 0.01) than the volumes of the day sannples. For intermediate 

 and deep levels the volumes of the day hauls exceeded those of the night hauls, but the differ- 

 ences were not statistically significant. 



Within the range of latitudes sampled, the area 2 S. to 8 N. contained the greatest amount of 

 zooplankton, with a peak in abundance near 1 S. latitude. 



The surface samples ranked considerably above the intermediate and deep samples in volume 

 and number of organisnns. There was no evidence of a concentration of zooplankton in the 

 region of the thermocline. 



The average size of organisnns in the collections increased with depth of sampling, and was 

 greater in the night hauls than in the day hauls except at the deep level, where the opposite 

 was true. 



The copepods were by far the nnost abundant group present in the sannples, followed by fora- 

 minifers, eggs, tunicates, gastropods, chaetognaths , radiolarians, crustacean larvae, 

 ostracods, euphausiids , siphonophores, and annphipods in that order. 



A detailed examination of collections obtained at two stations, one in the North Equatorial 

 Current and the other in the South Equatorial Current, provided little evidence of nnajor dif- 

 ferences in species composition between these two current sytems. 



Clarke-Bumpus sannplers equipped with 56XXX grit gauze nets retained large numbers of 

 small Copepoda, Foraminifera, and Appendicularia which passed through the coarser meshes 

 of 1 -meter nets of 30XXX grit gauze. The volunne of catch per unit of water strained was not 

 greatly different, however, for the two types of gear, indicating that with the larger net the 

 loss in small organisms was compensated by the less successful dodging of the larger 

 organisnns. 



