TABLE A, — Baja California, third quarter, summary of correlation tests: tuna, mean baitboat catch 

 per standardized day, with mean surface temperatures and zooplaakton volumes from CalCOFI 

 cruises. 



(YF) Yellowfin 



(•) Coefficient significant (P ^ 0.05) 



(♦) Coefficient positive 



(SK) Skipjack 



(••) Coefficient highly significant (P ^ 0.01) 



(-) Coefficient negative 



[Months with data in less than 9 I-degree squares are not listed; none of these coefficients were significant.] 



scarcest during the warmest years in the 

 thermal-equatorial region, season for season, 

 although figure 5 has not been constructed to 

 show this. 



From this and the infornnation for Baja 

 California, it is apparent that the northern 

 area of the skipjack fishery was enlarged and 

 the middle area reduced in 1957 and 1958. 

 For yellowfin, the northern area was likewise 

 enlarged; the middle area was not reduced 

 but fish were possibly scarcer in it. The 

 southern area (South America) was also en- 

 larged for both species by extension toward 

 the south, as shown in figure 5; according to 

 workers in the Inter-American Tropical Tuna 

 Commission, this change also was tempera- 

 ture-connected. The fishery was therefore 

 concentrated at the northern and southern 

 ends of its normal area, and the middle region 

 (southern Mexico-Central America) received 

 less attention than usual. This redistribution 

 of fish and fishing effort affected the investi- 

 gation in the Middle America region, where. 



in the outcome, it was impossible to get 

 information on abundance of tuna for some 

 areas in which oceanographic work was done 

 on STOR cruises. 



Brandhorst (1958) drew attention to the 

 partial similarity between charts of distri- 

 bution of zooplcinkton standing crop and ther- 

 mocline topography on the one hand, and tuna 

 abundance on the other. Therefore all avail- 

 able zooplankton measurements for the Middle 

 America region were assembled and compared 

 with the mean abundance of yellowfin and 

 skipjack in the same 1-degree rectangles and 

 months. The zooplajikton data were scanty 

 because of the small number of oceanographic 

 cruises. There were respectively 15, 14, 33, 

 and 24 1-degree rectangles, with both kinds 

 of information for the same month, for the 

 following cruises: SHELLBACK Expedition 

 (May-August 1952), EASTROPIC (October- 

 December 1955), SCOT or TO-58-1 (April- 

 June 1958), and TO-59-1 (January- February 

 1959). Zooplankton data have not yet been 



40 



