(0 to 5°N. lat.) suggests that If 1 t were possible to consider quantitatively the 

 higher vertebrate fauna as a whole, there might be better agreement In the hori- 

 zontal distribution of the groups of organisms at different trophic levels. 



However, the question still remains: Why does the zone with low numbers of 

 surface skipjack schools coincide with the zone of high numbers of deep-swimming 

 yellowfin tuna? Sampling is, of course, always suspect, particularly in this in- 

 stance, when the critical region (0° to 5°) is represented by only 16 days, though 

 these were well distributed In time and space. The possibility of competition with 

 other species was inferred above. An alternative hypothesis is that the vertical 

 distribution of food organisms In the region of low surface sightings differs in 

 such a way that the fish do not spend as large a fraction of their life at the svir- 

 face as they do In the adjacent areas to the north. Or, even if differences in the 

 vertical distribution of food organisms do not affect fish, the differences might 

 affect the density of aquatic birds, thus altering the apparent abundance of surface 

 schools of fish. 



STMMARY 



1. During the period October 17, 1950, to April 4, 1953, there were 546 days during 

 which surface trolling and bird and fish watches were maintained on POPI vessels 

 in the central Pacific. These observations have been separated into "Island" 



(0 to 60 miles from land), "semloceanlc" (60 to 180 miles from land), and 

 "oceanic" (more than 180 miles from land) provinces. 



2. The seasonal pattern of frequency of daily sightings in the Hawaiian Islands 

 area closely resembles the seasonal pattern of Ismdings of the commercial tiuia 

 fishery. The frequency of fish sightings appears to be a function of the abun- 

 dance of birds. 



3. The seasonal patterns in the Hawaiian, Line, and Phoenix islands are similar, 

 with greater frequency of sightings during the period June to November. 



4. Skipjack dominate the surface schools in the Hawaiian area, and yellowfin 

 dominate in the Line and Phoenix Islands. 



5. The frequency of sightings In semloceanlc areas Is approximately the same as in 

 the Island areas. 



6. The frequency of sightings in the oceanic areas in general was lower than in 

 island sind semloceanlc areas. 



7. Skipjack are evidently the dominant surface tuna in the oceanic and semloceanlc 

 areas, and surface yellowfin, if not dominant, at least are relatively more 

 abundant close to land. 



8. There Is an indication of seasonality in the abundance of surface schools In 

 the oceanic area, probably differing from the seasonal pattern in island and 

 semloceanlc areas. 



9. Trolling indicated a relatively high abundance of tunas, particularly yellowfin, 

 in the near proximity of Islands, with a uniformly low abundance in the seml- 

 oceanlc and oceanic areas. 



10. The evidence Indicates that the abundance of surface schools near islands In 

 the central Pacific Is a function of the standing crop of plankton. In the 

 oceanic area the abundance of surface schools and birds does not closely paral- 

 lel the abundance of plankton. 



16 



