FISHERY BULLETIN: VOL. 79, NO. 2 



batches (starting with the largest eggs) and calcu- 

 lated the mean major axis of eggs in each succes- 

 sive batch. The number of eggs per batch was 

 estimated from the wet weight of the females 

 using the batch fecundity Equation (4). 



As might be expected, the mean major axis of 

 eggs in each of the potential spawning batches for 

 the five females taken 24 h after spawning was 

 about one spawning batch out of phase from the 

 five nonspawning fish (Figure 4, upper). When the 

 most advanced spawning batch of the recently 

 spawned group was lagged by one spawning inter- 

 val, the function was the same for both groups 

 (Figure 4, lower) and similar to data on "non- 

 spa woiing females" in Hunter and Goldberg (1980). 

 The lower curves indicate that about four spawn- 

 ing batches of eggs >0.15 mm exist in the ovary of 

 females near spawning condition. Hunter and 



E 

 E 



I 

 o 

 I- 

 < 

 m 



o 



< 



CO 

 O 



UJ 



li. 

 o 



CO 

 X 



< 



O 

 < 



z 

 < 



UJ 



0.7 

 0-6 

 05 

 0.4 

 0-3 

 0.2 

 0-1 

 0.0 



I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 



2 3 4 5 6 7 8 9 10 II 12 13 14 15 

 ORDER OF SPAWNING BATCHES 



Figure 4. — Mean major axis of eggs in successive spawning 

 batches within the ovary of northern anchovy. Number of eggs 

 per batch estimated for each female from Equation (4). Numbers 

 on abscissa indicate order of spawning batch with 1 = the most 

 advanced batch. Circles are means of five nonspawning females 

 (no evidence of recent spawning!, and dots are means for five 

 females having spawned within 24 h (females taken in the 

 Southern California Bight); the X's are means for six females 

 with highly atretic ovaries taken in Monterey Bay in 1979. The 

 lower panel illustrates the correspondence between average egg 

 size in successive batches in nonatretic ovaries when recently 

 spawned females are lagged by one spawning batch interval. 

 Only the 15 batches containing the largest eggs are shown. 



Goldberg (1980) determined for 38 mature non- 

 spawning females that the mean size of eggs in the 

 most mature batch was 0.59 mm; and in the 5 

 females in the present analysis, the mean size was 

 0.71 mm. Thus a batch of eggs of 0.15 mm mean 

 size major axis would have to reach about 0.6-0.7 

 mm in about 4 wk (28 d) if females were to spawn 

 five or more times at weekly intervals. 



The ovaries of all laboratory females were 

 immature when the maturation experiment 

 began (elapsed time = 0, Figure 5) although 

 the mean size of eggs in the most advanced 

 spawning batch was quite variable among females 

 (mean egg size ranged from 0.13 to 0.48 mm). To 

 illustrate the rate of ovarian maturation we used 

 the average of the mean egg size in the spawning 

 batch of individual females (Figure 5). The rate of 

 maturation of ovaries in the laboratory group was 

 similar to that predicted from egg size frequency 

 distributions of wild fish, if one assumes spawning 

 in the sea occurs weekly (line. Figure 5). The 

 average of the mean size of eggs in the most 

 advanced spawning batch was 0.15 mm after the 

 first week of the experiment and was 0.62 mm 4 

 wk later. Thus maturation of eggs from 0.15 to 

 0.62 mm occurred in four wk and is about the same 

 as the theoretical estimate based on egg size 

 distributions in sea-caught specimens. This 

 demonstrates that the rate of egg maturation 

 required for continuous production of egg batches 



•a s 



q: 

 O Q 



S ^ 0.2 ^ 



ELAPSED TIME (days) 



Figure 5. — Maturation of eggs in the most advanced spawning 

 batch of laboratory-held northern anchovy as a function of 

 elapsed time. Maturity is achieved when average egg size in 

 batch attains 0.6-0.7 mm. Circles are averages of the mean size of 

 eggs in the most advanced spawning batch of females sampled on 

 a particular day, dots the median, and bars are ± 2 SE. Number 

 of eggs used to calculate the mean for each female was deter- 

 mined using Equation (4). The solid line is hypothetical matura- 

 tion rate of egg batches from 0.15 mm (major egg axis), assuming 

 females spawn at weekly intervals; the line is derived from data 

 in Figure 4. 



220 



