^JC UNSTON I . 



Figure 2. — Map of the central Pacific Ocean showing the demarcation Into "Island," 

 semloceanic," and "oceanic" provinces. Each dot represents the noon position 

 for a day's observation In the semloceanic and oceanic areas. The number of 

 days' observations In each Island area Is shown by the figures. 



These three groupings were made to correspond roughly with elements In the 

 habits of the birds and the fish which might affect their occurrence. We wished to 

 ascertain whether waters in the immediate vicinity of land might not afford an en- 

 vironment of a special character, perhaps supporting denser populations of tuna 

 than the offshore waters, for Relntjes and King (1953) have shown that the food of 

 yellowfin tuna captured near islands differs qualitatively from that of yellowfin 

 taken in the open ocean. The semloceanic zone (60 to 180 miles from land) is be- 

 yond the immediate influence of islands, judging by the stomach contents of the 

 yellowfin, but is within reasonable flight range for island-based birds. And fi- 

 nally, since birds are the chief indicator of fish, it was thoxight that some dif- 

 ference in apparent abundance might be noted between the semloceanic zone and the 

 truly oceanic areas beyond the possible daily flying range from islands, i.e., more 

 than 180 miles from land. 



Island Observations 



The observations from the vicinity of Islands were subdivided by Islands or 

 Island groups (fig. 2) and tabulated by four periods of the year roughly correspond- 

 ing to the temperate -zone seasons (table 1). The Hawaiian Islands group Includes 

 Hawaii, Lanai, Molokal, Maul, Oahu, Kauai, and Nilhau. The balance of the Hawaiian 

 Archipelago is designated as the Leeward Islands in table 1. For the purposes of 

 this discussion the Line Islands comprise Christmas, Fanning, Palmyra, Washington, 



