24° 

 N. 



22° 



20° 



_L 



MEXICO 



CAPE 

 CORRIENTES 



II4°W. 

 Figure 38.— 



112° 



110° 



108° 



106° 



Horizontal distribution of dissolved oxygen at the sea surface on part of CalCOFI cruise 6004-B and on cruise 

 TO- 60-1. The contour interval is 0.5 ml./l., here and in the next figure. 



where (Scripps Institution of Oceanography, 

 1967). 



Zooplankton and micronekton 



The standing crop of zooplankton was the only- 

 biological property which was routinely nneas - 

 ured on both cruises TO-60-1 and 6004-B. The 

 same net (described by King and Demond, 

 1953) was used in oblique hauls at similar 

 hauling speeds on both cruises, and displace- 

 ment volumes of catches from both cruises 

 were standardized in milliliters per 1,000 m. 

 of water strained. The data for TO-60-1 

 (Scripps Institution of Oceanography, 1967) 

 and for 6004-B* give such standardized vol- 

 umes for both total zooplankton and small 

 organisms; the following observations refer 



■^ Unpublished data. Bureau of Commercial Fisheries, 

 Fishery-Oceanography Center, La Jolla. Cal. 92037. 



to the small organisms, which were less 

 than 5 cm. in greatest dimension or less than 

 5 ml. in volume. 



The depths sampled by the oblique hauls 

 differed on the two cruises; the range was 

 about to 300 m. on TO-60-1 and about to 

 140 m. on 6004-B. A regression given by 

 Blackburn (1966) was used to estimate stand- 

 ardized volumes in the to 300-m. layer from 

 the standardized volumes measured in the to 

 140-m. layer on 6004-B, to make the two sets 

 of data as closely comparable as possible; 

 they were then combined to construct figure 40. 

 Contouring was done without regard to time 

 of day, the effect of which is probably small 

 on volumes from the 0-300 m. water layer. 



The areas with highest zooplankton volumes 

 broadly correspond to the areas of upwelling 

 or shoal thermocline which were recognized 

 in previous sections - -namely south from the 

 parts of the coast near Magdalena Bay and 

 Cape Falso, west from the part of the coast 



43 



