SMITH; SPAWNING BIOMASS OF NORTHERN ANCHOVY 

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Figure 9. — A time-series comparison of the annual quarterly average standard haul summation (Ahlstrom, 

 1968, double cross-hatch) and the annual quarterly average regional census estimate ("C", clear bar in- 

 cluding line C if any). 



and the major portion of increase of northern 

 anchovy is ascribed to the "central" subpopu- 

 lation which spawns off southern California. 



The seasonal contribution of anchovy larva 

 abundance from 1951 to 1966 is illustrated in 

 Figure 12. From 1951 through 1959, winter- 

 caught larvae dominated the total. Beginning 

 in 1960, spring larva abundance became increas- 

 ingly important and, in 1962, substantially ex- 

 ceeded winter larva abundance. As mentioned 

 above, the changing day-length in the spring 

 quarter makes an appreciable difference for 

 which the data have not yet been corrected. The 

 spring-caught larvae are underestimated as a 

 result. No correction has been applied for tem- 

 perature- or food-specific growth rate changes, 

 by season. 



The increase of numbers of anchovy larvae 

 shown in the foregoing regional census estimates 

 could result from the traditional spawning areas 

 being more completely covered with larvae, from 

 new spawning areas being covered, or there be- 

 ing more larvae per unit area. There are in- 

 stances of all three in the 1951-66 period. In 

 particular, in the southern California section of 

 the coast, where most of the increase took place, 

 the primary effect has been the additional cov- 



ering of traditional spawning areas. For ex- 

 ample, in the southern California offshore re- 

 gion, April through June, 7 of 50 tows contained 

 anchovy larvae in 1953, 25 of 48 tows contained 

 larvae in 1955, and 51 of 53 tows had anchovy 

 larvae in 1959 (14.0%, 52.1%, and 96.2% re- 

 spectively) . If one fits a regression line to the 

 increasing proportions of positive stations with 

 respect to anchovy larvae off southern California 

 the slopes in percent per year from 1952 to 1966 

 follow: 



"Winter S'pring Summer Fall 



Inshore (0-80 miles) 1 2 



Offshore (80-160 miles) 4 6 



Seaward (160-280 miles) 2 7 



1 

 4 

 2 



1 

 1 

 1 



Also, there are more anchovy larvae per posi- 

 tive station than before. In the years 1962-66 

 there are 5-8 times as many larvae per positive 

 station as in 1951 (Table 11). The number of 

 larvae per positive station is not independent 

 of the proportion of positive stations. One inter- 

 pretation of samples of larvae is that they are 

 drawn from relatively small (lOO's of meters, 

 Smith, in press) patches of larvae which are 

 dispersing in such a way that they tend to over- 

 lap. For example, for randomly distributed 



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