tudes along the northern edge of the North 

 Equatorial Countcrcurrent (Wyrtki, 1964, 

 1965). We have observed elsewhere (Blackburn 

 et al., 1970) that night micronekton does not 

 show a clear maximum in these latitudes, al- 

 though such a maximum might be expected, 

 and zooplankton shows one. The data m this 

 paper show a moderate maximum of skipjack 

 forage, especially in day samples, although we 

 do not know why day samples should give a 

 different picture. Possibly the distribution of 

 organisms is more even within the sampled 

 water column by day than by night. If the or- 

 ganisms that occur at night were restricted to 

 a thin layer of water (e.g., above the thermo- 

 clinc ) and occurred there in patches, oblique 

 hauls would sometimes under-sample them. 

 The forage maxima in the northwestern part 

 of the EASTROPAC area occur in an area of 

 relatively thick mixed layer (Wyrtki, 1964) 

 and low biological production (Blackburn, 

 1966). They represent occurrences of red 

 crabs, Pleiironcodcs phinipcs, that may have 

 been transported from the upwclling off the 

 coast of Baja California by the California Cur- 

 rent (Longhurst, 1967; Longhurst and Seibert, 

 1971). 



Regarding the relations of forage maxima 

 and minima to physical features and processes 

 in waters between 92 W and the coast, we 

 refer the reader to our observations published 

 elsewhere on maxima and minima of EASTRO- 

 PAC micronekton (Blackburn, et al., 1970). 



Three successful attempts have been made 

 to demonstrate the abundance of skipjack in 

 the EASTROPAC area since results described in 

 this paper were first announced. Hida (1970) 

 made a meridional crossing of the equator at 

 about long 119 W in October 1969 between 

 lat 6 S and 5 N. Skipjack were caught by 

 trolling or live-bait fishing along most parts of 

 the track, especially at three locations from 

 lat 2 to 5 N where over 100 fish (including 

 large ones) were caught with little effort at 

 each location. Trolling also gave very promising 

 results between lat 6 and 9 N at long 122 - 

 125 W. A few fish were taken by live-bait 

 fishing at about lat 4 S on long 119 W. Thus, 

 skipjack were reasonably abundant at lat be- 

 tween 4 S and 9 N, a range which normally 

 includes the northern equatorial forage maxi- 



mum, part of the southern equatorial maxi- 

 mum, and part of the zonal maximum that 

 occurs between lat 6 and 14 N. Williams 

 ( 1971 ) reported on skipjack caught by troUing 

 at various latitudes broadly along long 119 

 W in November and December 1970. The skip- 

 jack were most abundant in the region of the 

 northern equatorial forage maximum, specifi- 

 cally at lat 1 -5 N. One of us ( M. Blackburn) 

 led a similar cruise broadly along long 119 W, 

 in March and April 1971. On that occasion the 

 abundance of trolled skipjack was highest at 

 lat 9-11 N, and next highest at lat 1 -3 N; 

 skipjack forage was more abundant in both 

 those zones than elsewhere. Further informa- 

 tion about the cruises in 1970 and 1971 will 

 be published later. 



LITERATURE CITED 



ALVERSON, F. G. 



1963. The food of yellovvfin and skipjack tunas in 

 the eastern tropical Pacific Ocean. Inter-Am. 

 Trop. Tuna Comm., Bull. 7: 293-396. [English 

 and Spanish.] 



BLACKBURN, M. 



1965. Oceanography and the ecology of tunas. 

 Oceanogr. Mar. Biol. Annu. Rev. 3: 299-322. 



1966. Biological oceanogi'aphy of the eastern tropi- 

 cal Pacific : summary of existing information. 

 U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 540, 

 18 p. 



1968. Micronekton of the eastern tropical Pacific 

 Ocean: family composition, distribution, abun- 

 dance, and relations to tuna. U.S. Fish Wildl. 

 Serv., Fish. Bull. 67: 71-115. 



1969. Conditions related to upwelling which de- 

 termine distribution of tropical tunas off western 

 Baja California. U.S. Fish Wildl. Serv., Fish. 

 Bull. 68: 147-176. 



BLACKBURN, M., R. M. LAURS, R. W. OWEN, 

 and B. ZEITZSCHEL. 



1970. Seasonal and areal changes in standing 

 stocks of phytoplankton, zooplankton, and micro- 

 nekton in the eastern tropical Pacific. Mar, Biol. 

 7: 14-31. 



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