HUNTER and GOLDBERG SPAWNING INCIDENCE OF NORTHERN ANCHOVY 



Table 3- — Percent of female northern anchovy sampled off 

 southern California m February 1978 with hydrated eggs, and 

 postovulatory follicles ( age day and age 1 dayl by time of day. 



'Only fiydrated eggs, no postovulatory follicles 



^Includes some females witfi hydrated eggs and new postovulatory follicles 



time between 1900 and 2000, but were more com- 

 mon later in the night. As expected, the occurrence 

 of females with 1-day-old postovulatory follicles 

 showed no pattern with time of sampling. 



Despite our failure to obtain fish over the entire 

 night of spawning, the proportion of females in 

 February with hydrated eggs, combined with 

 those with new postovulatory follicles, was 19^7^ 

 and within the confidence interval for the estimate 

 based on 1-day-old postovulatory follicles (Table 

 2). 



February data indicate that spawning over a 

 2-wk period occurred at a rate of about 16 ±4*^ of 

 the population per night. This means that mature 

 females spawned every 6-7 days. The three purse 

 seine samples taken in March 1977 also indicated 

 a high frequency of spawning; 14^/f of the females 

 had 1-day-old postovulatory follicles and 9'^t had 

 new postovulatory follicles (Table 4). The March 

 collections were taken in the early morning after 

 spawning had ended, hence the new and 1-day-old 

 postovulatory follicles can be considered as sepa- 



rate estimates of spawning frequency for different 

 days. This line of reasoning leads to the conclusion 

 that the proportion of females spawning in March 

 may have been about 12% , equivalent to spawning 

 every 8 days. 



Of the 24 females taken in September, only 1 

 had hydrated eggs, 2 had new postovulatory folli- 

 cles, and none had 1-day-old postovulatory folli- 

 cles. Lower spawning activity would be expected 

 in September because egg and larval survey data 

 indicate peak spawning usually occurs in Feb- 

 ruary and March and has declined greatly by Sep- 

 tember although some spawning occurs through- 

 out the year (Lasker and Smith 1977). 



Sex Ratio and Incidence of Spawning 



The sex ratio of northern anchovy schools is 

 known to vary markedly from schools composed of 

 nearly all females to ones composed of nearly all 

 males (Collins 1969; Klingbeil 1978). It seemed 

 useful to determine if spawning activity varied 

 with sex ratio because the gi-eatest variability in 

 sex ratio occurs during the peak months of spawn- 

 ing (Klingbeil 1978), Twenty-five fish from each 

 trawl sample taken in February 1978 were sexed. 

 We grouped these samples into three classes on 

 the basis of sex ratio (number of females/( males -i- 

 females)) and calculated the proportion of females 

 in each of the three sex ratio classes that fell 

 within the following reproductive classes: spawn- 

 ing on the night of capture (females with hydrated 

 eggs or new postovulatory follicles); spawning on 

 the night before capture (females with 1-day-old 

 postovulatory follicles); and no evidence of spawn- 

 ing (none of the above categories). 



Table 4.- 



-Reproducti ve state of female northern ancf 11 ivy collected in March 1977 and September 1977 off 

 southern t alifomia. 



647 



