BLACKBURN and WILLIAMS: DISTRIBUTION AND ECOLOGY OF SKIPJACK TUNA 



I20°W 



II5"W 

 _i 1 1 1_ 



FORAGE 

 ml/ lOOOm^ 



IO°N- 



< 25 

 .25-5 

 5 -10 

 >l 



5'N- 



5"S 



I20*W 



Figure 25.-Day standing stock of skipjack forage (ml/1,000 m') 

 (combined Part I and II data), cruise Jordan 60, March-April 

 197L 



I20°W 



15-N I5"N 



II5"W 



lO'N lO'N 



5*N 5'N 



FORAGE 

 ml/ 1000 m^ 



<25 



25-50 

 50-10.0 

 >I00 



5«S 



IB'N 



IO*N 



■5*N 



-4-5*S 



I20»W 



Figure 26.-Night standing stock of skipjack forage (ml/ 1,000 

 m^) (combined Part I and II data), cruise Jordan 60, March-April 

 1971. 



the lower coefficient could have been so high with 

 no correlation, and a corresponding chance of only 

 about one in 200 for the higher coefficient. There 

 seems no reason to presume nonsignificance, at 

 least for the higher coefficient. 



Significant correlations were not obtained for 

 any data from the March-April cruise. Only two 

 degrees of freedom are available to test the sig- 

 nificance of correlations corresponding to the sig- 

 nificant correlations in the November-December 

 data. In any case the meager forage data for 

 March- April seem not to have adequately depicted 

 the actual conditions, as noted above. Relations of 

 skipjack to forage are discussed later. 



CRUISE 116 OF 



RV CHARLES H. GILBERT, 



OCTOBER-NOVEMBER 1969 



In October-November 1969, the RV Charles H. 

 Gilbert of the Honolulu Laboratory of the National 

 Marine Fisheries Service made a cruise to collect 

 samples of skipjack and other tunas for a sub- 

 population study. The main fishing operations 

 were located in the same area as the combined 

 cruise Jordan bl-Cromwell 51, though approx- 

 imately 1 yr earlier. The fishing and environmen- 

 tal data are analyzed here in more detail than by 

 Hida (1970). Figure 27 shows the cruise track of 



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