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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



I interpret the differences in the ratios between 

 1929-30 and 1946 as real. I seriously question 

 that they could be due to differences in techniques 

 or interpretation of modes by Clark and myself. 

 There have been three investigators working on 

 the data I have presented in table 10, and the 

 three of us have obtained comparable results. If 

 the ratios are any indication of the average num- 

 ber of batches spawned per female sardine, then 

 the number of batches must vary considerably 

 from year to year. One implication of this is that 

 when basing population estimates on egg surveys 

 and fecundity data, it may be necessary to have 

 current determinations of both egg abundance 

 and average fecundity for that season. 



I find that there is no significant difference 

 among ratios of the 113 females considered in 

 table 10 when grouped by size (standard length) 

 rather than stage of maturity (table 12). Clark 

 postulated that larger fish mature earlier than the 

 smaller fish and spawn over a longer time interval. 

 My study does not indicate a higher ratio (of 

 smaller ova to ova in the most advanced mode) 

 in larger female sardines. Hence, if larger fish 

 spawn more batches of eggs in a season than 

 smaller fish, these additional batches are not 

 evident in maturing ovaries. Therefore if larger 

 fish are to spawn more batches of ova than smaller 

 fish, one of the following two conditions must be 

 fulfilled: either additional ova are added to the 

 mass of smaller yoked ova from the reservoir of 

 non-yoked ovocysts, or, if this does not occur, then 

 larger fish must spawn a larger proportion of the 

 smaller yoked ova present in the initial maturation 

 period than do smaller fish. If the first condition 

 obtains, then there would be little significance to 

 ratio changes during the season. If the second 

 condition obtains, then only part of the smaller 

 yoked ova initially present in the developing ovary 

 would eventually mature and be spawned. Hence, 

 smaller fish should have a larger number of 

 batches of degenerating ova at the termination of 

 their spawning than the larger fish. With regard 

 to the 1946 samples, the average ratio of 1.5 to 1 

 shows that an average of only 2.5 batches could be 

 spawned if all yolked ova were matured and 

 spawned, and no additional yolked ova were 

 added during the spawning season. If a portion 

 of these degenerate, then the average number of 

 batches spawned per female sardine must be 

 between 1 and 2.5 batches. 



Andreu (1951) postulated that the peak spawn- 

 ing season of the European sardine, as measured 

 by the occurrence of planktonic eggs (Hickling 



Table 12. — Frequenries of ratios of number of all smaller 

 yolked ova to the riiituher of yolked ova in the most advanced 

 group (taken as unity) grouped by fish size (standard 

 length) 



1945) off Plymouth, was too restricted in time 

 to allow the sardines to mature and spawn more 

 than one modal group of eggs in a spawning 

 season. This could also be inferred for the 

 Pacific sardine from table 12, and the ovum 

 growth rates postulated by Clark (1934:29): 

 ". . . probably slightly more than two months 

 are necessary for eggs to grow from stage C 

 [last mode between 0.26 and 0.34 mm.] to stage 

 G [last mode between 0.64 and 0.74 mm.]," and 

 ". . . approximately three or four weeks will 

 elapse before females in stage G reach maturity." 

 Clark's figures show modal egg diameters for 

 groups of translucent ova ranging from 0.80 to 

 over 1.30 mm. According to Ahlstrom (1950:134- 

 135), "Fertilized eggs average about 1.70 mm. in 

 diameter (range 1.35-2.05 mm.)," pre-cleavage 

 eggs "taken during the four hour period before 

 midnight are considerably smaller in diameter 

 than are those with some embryonic development. 

 Since the yolks are of similar size in both groups. 



