FISHERY BULLETIN: VOL. 84, NO. 3 



number of spawnings and the fecundity on a 

 monthly basis for age groups 1, 2, 3, and 4 + . 

 Average monthly wet weight by age was taken from 

 Mallicoate and Parrish (1981). The number of 

 spawnings per month was calculated from the num- 

 ber of days per month and the index of daily spawn- 

 ing (i.e., the proportion of stages 5 + 6). Note that 

 the bias due to the unknown sex problem discussed 

 earlier would tend to cause an overestimation of the 

 daily spawning incidence: particularly in females in 

 their first spawning season. Also note that the in- 

 dex of daily spawning underestimates the spawn- 

 ing incidence by about 5%. 



Our analysis shows that there are large, age- 

 dependent variations in the proportions of female 

 northern anchovy spawning as the spawning season 

 progresses (Fig. 10). From July until January all age 

 groups have a very low daily spawning index. Inten- 

 sive spawning commences in February and all age 

 groups have roughly the same spawning index 

 (9-12%). In March the spawning index of age group 

 1 declines to about 2%; it increases slightly in April 

 and declines to about 1% in May. In age group 2 the 

 spawning index increases to 13% in March and then 

 declines to about 2% by May. Age groups 3 and 4 + 

 have peak spawning indices in March (25 and 27%), 

 considerable spawning in April (10 and 17%) and 

 lesser amounts in May (3 and 6%) and June (3 and 

 6%). 



Older females have a much larger number of 

 spawnings per spawning season than younger 



~i 1 1 1 r 



JUL RUG SEP OCT NOV DEC JflN FEB MflR RPR MAY JUN 



MONTH 



Figure 10.— The monthly percentages of female northern 

 anchovies with maturity stages 5 + 6, by age group. 



females (Table 3). In their first spawning season 

 females have an average of 5.3 spawnings. In their 

 second spawning season this rises to 11.9 and in 

 their third and fourth plus seasons the number of 

 spawnings rises to 19.2 and 23.5. The increase in 

 the number of spawnings associated with increas- 

 ing age appears to be primarily due to the increase 

 in the length of the spawning season that occurs in 

 older fish. The average number of spawnings per 

 season for all females sampled was 15.1. This is less 

 than the estimate that Hunter and Leong (1981) 

 developed from the energetics of female northern 

 anchovy (i.e., 20 spawnings per year). Their calcula- 

 tions indicated that mature female northern anchovy 

 spawned on the average 15 times between February 

 and September; their calculation of the number of 

 spawnings from October to January (5) was esti- 

 mated indirectly from the relative monthly larval 

 abundance in 1953-60. Our estimate of the number 

 of spawnings from February to September (14.3) is 

 very close to the Hunter and Leong (1981) estimate 

 which was based on a smaller histology data set. 

 However, our estimate of the number of spawnings 

 from October to January is only 0.8 and is much less 

 than their indirect estimate based on the relative 

 seasonal larval abundance for the 1953-60 period. 

 The central stock of northern anchovy was at a much 

 smaller population size in 1953-60 than it was in 

 1966-84 (MacCall 1980) and northern fish, with a 

 seasonal spawning pattern similar to that occurring 

 in the Monterey data, may have comprised a larger 

 proportion of the anchovy population off California 

 during the 1953-60 period than at present thus in- 

 flating Hunter and Leong' s estimate for the 

 October-January period. 



Our analysis indicates that annual fecundity in the 

 central stock of northern anchovy is heavily age 

 dependent; the average 4 + yr-old female produces 

 nearly 10 times as many eggs as a 1-yr-old female 

 (Table 3). Our calculations show that central stock, 

 female anchovy produce 2,803, 6,550, 11,434, and 

 13,861 eggs/g of body weight per spawning season 

 in their 1st, 2d, 3d, and 4th plus spawning seasons. 

 Females 4 yr of age and older produce nearly 5 times 

 as many eggs per unit of weight as 1-yr-olds. 



DISCUSSION 



Over the last decade it has become apparent that 

 recruitment failure is the major threat to many of 

 the world's largest fisheries. In addition, variation 

 in recruitment is a significant causal factor in the 

 interyear variation of the annual catches of many 

 fisheries. Stocks of small pelagic fishes appear to 



514 



