II4°W. 112° 110° 108° 106° 



Figure 39. — Horizontal distribution of dissolved oxygen at 50-m. depth on part of CalCOFI cruise 6004-B and on TO-60-1. 



north of Mazatlan, and west from Cape Cor- 

 rientes. The 100 ml. /l, 000 m.^ contour of 

 zooplankton in figure 40 and the 17° C. isotherm 

 at 50 m. in figure 30 correspond rather well. 

 As mentioned above, the area off Cape False 

 was moderately rich in both inorganic phos- 

 phorus and chlorophyll, and the areas north 

 of Mazatlan and west of Cape Corrientes 

 were fairly rich in one or the other of these 

 properties . 



Standardized volumes of zooplankton from 

 night surface hauls (5 m. deep), made on cruise 

 TO-60-1 only, show a different distribution 

 (not illustrated here). Volumes over 300 ml./ 

 1,000 m.-' occur in two areas--one running 

 southwesterly from an area about halfway 

 between Cape Falso and Mazatlan, and the 

 other west of Cape Corrientes. The latter 

 area agrees and the former area does not 



agree with the distribution of highest volumes 

 from the oblique hauls (fig. 40), 



The micronekton (Blackburn and Associates, 

 1962) was sampled from the upper 90 m. 

 (approximately) at 14 night stations on cruise 

 TO-60-1 only. The highest concentration (137 

 ml. /l, 000 m.^) was at station 59, inshore of 

 Tres Marias Islands, and the next highest 

 (30 ml. /1, 000 m.3 ) at station 37, off Mazatlan. 

 Other values ranged from 1 to 13 ml./ 1 ,000 m.^ 

 Blackburn (1966) discussed the relations be- 

 tween the following standing crops from the 

 same or adjacent stations on cruise TO-60-1 

 and other cruises in the eastern tropical 

 Pacific: micronekton at to 90 m. (fish and 

 cephalopods combined), zooplankton at to 

 300 m. (total small organisms and copepods 

 only), and chlorophyll a at to 100 m. Crops 

 of zooplankton and micronekton tended to be 

 higher for the same amount of chlorophyll a 

 on TO-60- 1 than on other cruises. 



44 



