During the suimner of 1952 the skipjack catch for the Hawaiian 

 Islands was about half that of the prerious summero The zooplankton 

 volumes on the other hand ( Smith cruise 17) ^ as previously stated^ v:ere 

 considerably larger in the late summer than in the year before (Smith 

 cruise 12 ) » The T-S curve representing data collected in September 1952j 

 on Smith cruise 17j, has not yet been worked outo 



COMPARISONS WITH ZOOPLANKTON ABUNDANCE OF OTHER REGIONS OF THE PACIFIC 



As previously stated (po 4)^ the Challenger expedition visit- 

 ed the Hawaiian Islands in 1875 o i<iualitative surface hauls were made 

 at intervals while enroute from Japan to Hawaii and from Hawaii to 

 Tahitio Although apparently no measurements v/ere made of the total 

 numbers of organisms nor the volumes of the samples to permit detailed 

 comparisons between areas » Tizard et alo (1885) reported that for the 

 portion of cruise from Hawaii to Tahiti "The tow-net gatherings were 

 very productive throughout the trip^ the abundance of life in the 

 Equatorial and Counter Equatorial Currents being verj"- remarkable both 

 for the number of species and individuals u" 



The Carnegie traversed the central pacific during the fall 

 of 192 9 o Vertical plankton hiauls from depths of 100 and 150 meters 

 were made v.'ith a ^meter net of Noo 15 silk bolting clotho Dry weights 

 of the plankton samples varied from 90 and 140 mg„ for tv/o stations 

 (stations 139 and 140) about 100 miles north of the Hawaiian Islands 

 to values as great as great as 520 mgo at about 5^ No latitude (station 

 155) and 450 mgo at about 2° So latitude (Graham 1941) » 



During the years 1950 to 1952 quantitative zooplankton 

 collections v;ere obtained by the Hugh Mo Smith on ten cruises in the 

 equatorial Pacific between 120*^ Wo and~180o Y.^o longitude o TAfhen the 

 resulting data are combined for this range of longitude and then 

 separated into 5° latitiadinal groups ^ they present the picture shoi/vn 

 in figtire 16 ^ It is evident that within this range of latitude the 

 greatest standing crop of zooplankton occurred in the region of the 

 Equator o This increased productivitj'' is the result of upwelling at 

 the Equator associated with the equatorial divergence » which replen- 

 ishes the supply of nutrients in the euphotic zone and creates es- 

 pecially favorable conditions for the growth of plant and animal 

 life (Graham 1941^ Sverdrup et alo 19429 Cromwell 1951;, 19535 King 

 and Demond 1953) o 



The amount of zooplankton in the Hawaiian area was greater 

 than in certain regions of the North Equatorial Current (10° to 15° 

 No latitude and 20° to 25° No latitude) and of the South Equatorial 

 Current (5° to 10° So latitude) ^ but was distinctly less than that 

 found in the "rich zone" from 5° So to 5° No latitude o We believe 

 that these differences in zooplankton abundance are indicative of 

 differences in basic productivity among these various regions of the 

 central Pacifico 



47 



