FISHERY BULLETIN: VOL. 70, NO. 1 



.90[— 

 SO- 

 TO- 

 .60- 

 50- 

 .40- 

 30- 

 20- 

 .10- 



1 



LONGITUDE 140* W 

 r--.754 



a LEG I 

 o LEG 2 

 X LEG 3 

 Q LE6 4J 



HMS 15 



3. 



< 

 I 

 0. 



I/) 

 o 



X 



a. 





 90 



.80 



.70 



.60 



.50 



.40 



30 



20 



10 





 .90 



60 



.70 

 .60 

 .50 

 .40 

 .30 

 .20 

 .10 

 



Table 3. — Relation of temperature to phosphate in the 

 zone of lat 1° to 5°N\ 



LONGITUDE I69'-I72»W 

 r«-.809 



HMS 2 

 X HMS 5 

 o HMS 8 

 » HMS 14 



_L 



25" 



26" 27° 



TEMPERATURE 'C 



28* 



Figure 27. — Relations between temperatures and inor- 

 ganic phosphate between lat 1° and 5°N. 



and also providing single or closely adjacent 

 longitudes are considered. 



Unfortunately, there is not enough material 

 available for a rigorous examination of surface 

 temperature-phosphate ratios. The available 

 data (Figure 27) between lat 1° and 5°N behave 

 in a manner consistent with the hypothesis. 

 Along each longitude is the expected negative 

 regression with respect to temperature. The 

 heterogeneity among longitudes is indicated by 

 the reduced value of r (Table 3) when all data 

 are considered together. 



Zoopkinkton. — The relation between temper- 

 ature and zooplankton should theoretically be a 



1 Data from Cromweill (1954), Austin (1954a, b), and Stroup (1954). 

 Each temperature and phosphate measurement is from the Nansen bottle 

 immediately below the surface bottle, generally at about 10 m. 



curve skewed to the right, for time should elapse 

 between enrichment and peaking of the copepods 

 that form the bulk of the catches. We already 

 know, however, that the peak of zooplankton is 

 coincident or nearly so with the center of up- 

 welling, and since we have restricted ourselves 

 to the zone north of the upwelling (lat 1°-5°N), 

 we should expect to find only the descending limb 

 of the curve. 



The plots in Figure 28 indicate a significant 

 negative relation between temperature and zoo- 

 plankton, though the relation is not as striking 

 as that between temperature and phosphate. 

 Some of the variability may be attributable to 

 sampling errors and some to systematic errors, 

 such as day-night variation. As in the instance 

 or the phosphate, the values of the correlation co- 

 efficients are higher (except for long 140°W) for 

 the individual sections than for the data as a 

 whole (—0.472, —0.718, —0.679 versus —0.567 

 for all data). 



Yellowfin tuna. — We have shown that matur- 

 ity of the water, as indicated by the temperature 

 of the mixed layer, appears significantly related 

 to the amount of dissolved nutrients (phosphate) 

 and the amount of zooplankton. It remains to 

 project this reasoning up the trophic levels to 

 yellowfin tuna. Probably one or more trophic 

 levels must intervene between the zooplankton 

 sampled and tuna, for King and Demond (1953) 

 showed the zooplankton to be mainly copepods, 

 and Reintjes and King (1953) showed that, al- 

 though yellowfin tuna consume a variety of or- 

 ganisms, the bulk of their diet is composed of 

 squid and fish. 



898 



