the more nutritious zooplankton per unit of 

 water strained. 



The night hauls yielded volumes averaging 

 1.49 times the volumes of day hauls. A 

 method of adjustment was ennployed to re- 

 duce these differences associated with the 

 hour of hauling. 



A short series of experimental hauls indi- 

 cated the superiority of night over day and 

 0- to lOO-nneter over 0- to 200-meter hauls 

 in the catch of zooplankton and of fish larvae. 



The distribution of zooplankton was remark- 

 ably uniform throughout the island waters. 

 Fronn an analysis of variance we concluded 

 that there were no significant differences 

 between cruises, between windward and 

 leeward areas, or annong six subareas. 



Although the physical and chemical environ- 

 ments are also quite uniform in general re - 

 spects, the surface currents are exceedingly 

 complex and are characterized, particularly 

 on the leeward side of the islands, by large 

 vortices or eddies. We found no evidence 

 that the eddies had any influence on the vol- 

 ume of zooplankton. Also evidence of the 

 effects of upwelling, land drainage, or other 

 littoral influence was obscure or lacking. 



There was a trend of increasing zooplank- 

 ton abundance from March to July; our data 

 are not adequate, however, to provide a 

 complete seasonal picture. Although sur- 

 face temperature and the catch of the 

 Hawaiian skipjack fishery also increase 

 during the spring and early summer nnonths , 

 we doubt that there is a direct relationship 

 among these variables. 



KING, J. E. , and T. S. HIDA 



1954. Variations in zooplankton abundance 

 in Hawaiian waters, 1950-52. U. S. 

 Fish and Wildlife Serv, , Spec. Sci. 

 Kept. --Fish. No. 118, 66 p. 



, and I. 1. IKEHARA 



1956. Comparative study of food of bigeye 

 and yellowfin tuna in the central 

 Pacific, U. S. Fishand Wildlife Serv,, 

 Fish. Bull. 57(108): 61-85. 



McGARY, J. W. 



1955. Mid-Pacific oceanography, Part VI, 

 Hawaiian offshore waters, Decen-iber 

 1949 - November 1951. U. S. Fish 

 and Wildlife Serv. , Spec. Sci. Rept. -- 

 Fish. No. 152, 138 p. 



REINTJES, J. W. , and J. E. KING 



1953. Food of yellowfin tuna in the central 

 Pacific. U. S. Fish and Wildlife Serv. , 

 Fish. Bull. 54(81): 91-110. 



SECKEL, G. R. 



1955. Mid-Pacific oceanography, Part VII, 

 Hawaiian off shore waters, September 

 1952-August 1953. U, S. Fish and 

 Wildlife Serv., Spec. Sci. Rept. -- 

 Fish. No. 164, 250 p. 



YAMASHITA, D. T. 



195 7. Statistics of the Hawaiian skipjack 



fishery. U. S. Fish and WildlifeServ, , 

 Fish. Bull. (In press) 



9. Zooplankton volumes were not significantly 

 correlated with water temperature, salin- 

 ity, inorganic phosphate, thermocline depth, 

 or skipjack catch. This lack of correlation 

 between zooplankton and those factors con- 

 sidered most likely to have biological sig- 

 nificance may indicate that other, nnore 

 fundamental factors of the environment may 

 be the causative agents for the variations 

 observed. 



LITERATURE CITED 



KING, J. E. , and JOAN DEMOND 



1953. Zooplankton abundance in the central 

 Pacific. U. S. Fish and Wildlife 

 Serv., Fish. Bull. 54(82): 111-144. 



15 



