of these conditions are just the reverse of that 

 found for the zooplankton as a whole. 



GEOGRAPHICAL AND TEMPORAL VARIATIONS 



Oceanographic observations have shown 

 that Hawaiian waters provide a comparatively 

 homogeneous environment both in time and 

 space in respect to surface temperature, sa- 

 linity, and inorganic phosphate. The surface 

 current pattern, however, is of con^plex nature 

 (fig. 5) and is characterized, particularly to 

 the leeward of the islands, by large cyclonic 

 or anticyclonic vortices (McGary 1955, Seckel 

 1955). A comparison of sigma- t and inorganic 

 phosphate cross-sections has indicated that en- 

 richment of the surface layers through lateral 

 mixing associated with these eddies is insigni - 

 ficant (McGary 1955). There are, therefore, 

 no a priori reasons to expect large variations 

 in plankton abundance either geographically or 

 seasonally. The relatively slight but consistent 

 variations that do occur are noteworthy, however. 



In figure 6 we have attempted to show 

 areas of similar zooplankton concentration for 

 the two cruises of the Smith which employed 

 oblique hauls to 200 meters depth and afforded 



general coverage of the area. Although the 

 results indicate conditions of remarkable uni- 

 fornnity throughout the island waters, there were 

 certain localities which, in agreement with past 

 sampling, were generally richer or poorer than 

 other areas. For example, stations southwest 

 of Oahu produced volumes higher than average, 

 and the eastern portion of the survey area again 

 produced consistently low catches. The area 

 north to northeast of Kauai, which was consider- 

 ably above average on two earlier cruises (King 

 and Hida 1954), yielded only one unusually large 

 sample. 



From an analysis of variance of com- 

 pletely randomized design, employing the zoo- 

 plankton volunnes from cruises 20 and 21, we 

 conclude that there were no statistically signi- 

 ficant differences (P > 0.05) between cruises, 

 between windward and leeward areas, or annong 

 the 6 subareas with boundaries as shown in fig- 

 ure 2. In an analysis of earlier data we found 

 significant differences (P < 0.05) among cruises 

 but no significant differences among areas or 

 subareas (King and Hida 1954). Despite the lack 

 of statistically significant differences among sub- 

 divisions of the region, the repeated occurrence 

 of low catches to the east or just upstream of the 



Figure 5. --Dynamic height anomalies (dynamic nneters) at the 

 surface relative to 500 m. , Hugh M. Smith cruise 21, August 

 1953, Contour interval 0.02 dynamic meters. [From Seckel 

 1955, fig. 29] 



