Date for the several years are only roughly comparable since the coverage 

 was somewhat different in each year. Only a portion of the spawning range of 

 the jack mackerel is surveyed on CCOFI cruises, and it is likely that a variable 

 portion of the population is within the survey area in successive seasons. The 

 most striking change in distribution of jack mackerel larvae In 1957 was the 

 marked decrease in abimdance off central and southern Baja California. Nearly 

 30 percent of jack mackerel larvae were taken in the area off central Baja Cali- 

 fornia (station lines 110-137) in 1956, and over 20 percent in 1955, while only 3 

 percent occurred in this area in 1957, The northward shift in distribution of jack 

 mackerel larvae Is probably related to the warmer water temperatures prevail- 

 ing In 1957. 



The seasonal distribution of larger jack mackerel larvae (6.26 mm. and 

 larger) during 1957 is compared with the distributions of the preceding five 

 years in the following tabulation: 



Seasonal abundance of larger jack mackerel larvae (6,26 mm, 

 and over), 1952-1957 (standard haul totals) 



Months 



Total 



1952 



620 



1953 



1954 



1955 



620 



417 



730 



1956 



392 



1957 



779 



There was a marked peak in the abundance of larger larvae in June, 1957. A 

 similar pattern of seasonal abundance was found in 1952 through 1954. The seasonal 

 distributions In 1955 and 1956 were bimodal, however; peaks in abxmdance of larger 

 larvae occurred in April and July during 1955 and in March and June of 1956. The 

 numbers of larger larvae taken in June 1957 were markedly greater than during any 

 other one month, but the season total was not much larger than that for 1955, 



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