384 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 5. — Correlations of adjusted zooplankton volumes (cc./lOOO m?) as the A'l variate, with A'2 variate the surface inorganic 



phosphate or yellowfin longline catch from same locality 



Xj variate 



Motor vessel and cruise No. 



Range o( latitude 



Inorganic phosphate, fig at/L. 

 Inorganic phosphate, Mg at/L. 

 Inorganic phosphate, /xg at/L. 

 Inorganic phosphate, Mg at/L. 

 Yellowfln catch pi-r 100 hooks 

 Inorganic phosphate, Mg at/L. 

 Yellowfin catch per 100 hooks 

 Inorganic phosphate, ttg at/L. 

 Inorganic phosphate, Mg at/L. 

 Yellowfin catch per 100 hooks 



Hugh M. Smith— 2... 

 Hugh M, Smith— 5... 

 Hugh M. Smith— 8-.. 

 Hugh M. Smith— 11.. 

 Hugh M. Smith— 11.. 

 Hugh M, Smith— 14.. 

 John R. Manning — 11 

 Hugh M. Smith— 15.. 

 Hugh M. Smith— 18.. 

 Hugh M. Smith— 18.- 



24° N.-S" S. 

 27° N.-5° S. 

 21° N.-14° S 

 19° N.-4° S. 

 15° N.-5° S. 

 9° N.-8°S.. 

 8° N.-8° S... 

 9° N.-7° S.., 

 9° N.-9° S... 

 9° N.-9° S.. 



<0.01 

 <0.01 

 <0.01 

 <0.01 

 0.05 

 >0.05 

 >0.06 

 <0.05 

 >0.05 

 >0.C8 



• In this instance zooplankton volumes obtained by Hugh M. Smith cruise 14 were correlated with longline catches of John R. Manning cruise 11, the two 

 cruises occurring during the same period of time. 



tween surface inorganic phosphate and zooplank- 

 ton volumes (table 5). With a short series of sta- 

 tions the correlation may be nonsignificant as 

 that for the Hugh M. Smith cruises 14 and 18, or 

 even be significantly negative as for cruise 15. 

 The latter is perhaps an example of an inverse 

 relation resulting from high utilization. The cor- 

 relation of zooplankton volume and yellowfin 

 catch was significant (P = 0.05) for Hugh M. Smith 

 cruise 11, but non-significant for cruise 11 of the 

 John R. Manning and cruise 18 of the Hugh 

 M. Smith. 



Within the equatorial "rich zone," from the 

 southern boundary of the Count ercurrent at about 

 5° N. latitude to 5° S. latitude, zooplankton and 

 yellowfin showed a gradient of increasing abund- 

 ance between 180° and 150° W. (fig. 20). The 



» — = ZOOPLANKTON VOLUME 



o -o SURFACE INORGANIC PHOSPHATE 



„ „ YELLOWFIN CATCH 



O 40 

 O 



o 



O 30 



o 

 o 



2 S 



o 



160 160 140 



WEST LONGITUDE 



130 



120 



FifitiRE 20. — Longitudinal variations in yellowfin longline 

 catch, zooplankton volumes (adjusted) and surface 

 inorganic phosphate for the South Equatorial Current 

 from the southern boundary of the Countercurrent, at 

 about 5° N. latitude to 5° S. latitude, with the data 

 segregated by 10-degree intervals of longitude. 



yellowfin catch continued high at 140° W. and 

 then dropped off sharply to the east, while zoo- 

 plankton volume varied somewhat irregularly to 

 the east but remained moderately high. The 

 variation in surface inorganic phosphate was 

 roughly just the reverse (fig. 20), with high 

 concentrations on the eastern and westernmost 

 longitudes and low values in between. We have 

 no empirical explanation at present for this 

 distribution of phosphate. It may possibly result 

 from differences in rate of utilization as the most 

 productive areas appear to be the mid-longitudes. 

 In the equatorial region of the central Pacific, 

 July, August, and September was the period of 

 best yellowfin catch (fig. 21). It was also the 

 period of highest zooplankton abundance, al- 

 though the quarter October, November, and 

 December was essentially of equal rank. Phos- 



ZOOPLANKTON VOLUME 

 SURFACE INORGANIC PHOSPHATE 

 YELLOWFIN CATCH 



2 S 



q 



JAN-Fee-MAR APR-MAY-JUN JUL-AUG'SEP OCT-NOV-OEC 



Figure 21. — Seasonal variations in yellowfin longline 

 catch, zooplankton volumes (adjusted) and surface 

 inorganic phosphate for the South Equatorial Current 

 from the southern boundary of the Countercurrent at 

 about 5° N. latitude to 5° S. latitude, with the data 

 segregated into quarterly periods of 3 months each. 



