Hunter et al . Fecundity, spawning, and maturity of Microstomus paclflcus 



15 



where r^ is the coefficient of determination, and 

 CV(h) is the coefficient of variation for the regression 

 coefficient (b). The coefficient of determination {r~) 

 for Dover sole total fecundity and fish weight was 0.58. 

 Thus 73 females are required for a CV(h) = 0.10. In con- 

 clusion, two tissue samples from each of 70-80 Dover 

 sole females were adequate for expressing the relation 

 between weight and total fecun- 

 dity, if a CV(h) of about 0.10 is 

 desired. 



qualitative analysis that recruitment of stage-2 oocytes 

 into the advanced stock probably ends when the mean 

 diameter of stage 3 is between 0.8 and 0.9mm. 



We conducted a stepwise multiple regression analysis 

 of total fecundity (Yp) on mean diameter of the ad- 

 vanced oocytes (D) and female weight (W) for females 

 taken off Oregon in November-December. The coeffi- 



Relation to ovarian 

 development 



The optimum time for estimating 

 potential annual fecundity is 

 early in the spawning season 

 when the probability of spawning 

 is low. Estimates taken in this 

 period may be biased because all 

 oocytes may not have been 

 recruited into the advanced stock 

 of yolked oocytes. In this section, 

 we use Oregon Dover sole taken 

 in November-December to ex- 

 amine the recruitment of oocytes 

 into the advanced stock of yolked 

 oocytes. 



If substantial numbers of 

 oocytes are maturing from early- 

 yolked to more advanced stages, 

 one would expect an overlap in 

 the size distributions of oocytes 

 in different development stages. 

 When vitellogenesis of the early 

 yolked oocytes does not continue, 

 one would expect that a gap 

 would develop between the less- 

 advanced and the most-advanced 

 oocytes as the yolked oocytes 

 continued their maturation. In 

 Dover sole, the diameter distri- 

 butions of stage- 1, -2, and -3 

 oocytes broadly overlap when the 

 mean diameter of the advanced 

 yolked oocytes (stage 3) is less 

 than 0.7 mm (Fig. 6). The extent 

 of overlap declines as the stage-3 

 oocytes grow from 0.7mm to 

 0.8mm. Separation of the ad- 

 vanced stock (stage 3) from the 

 other vitellogenic stages (1 and 

 2) becomes complete as the ad- 

 vanced stock grows from 0.8 to 

 0.9 mm. It appears from this 



T3 



ra 



D 

 O 



0.88 



0.96 



■I'l "T "T" T"r ' I "I'TT T 'T -T 



0.2 0.3 0.4 0.5 0.8 0.7 0.8 0.9 1.0 1.1 ' 0.2 0.3 0.4 5 0.6 0.7 0.8 0.9 1.0 1.1 



OOCYTE DIAMETER (mm) 



Figure 6 



Frequency distribution of oocyte diameter of three vitellogenic oocyte stages in ovaries 

 of Dover sole Microstomus ipacijicus. Each panel represents the ovary from one 

 female. Fish arranged in order of the mean diameter of the advanced yolked oocytes, 

 stage 3 (which is shaded); numbers and arrows indicate mean diameter of stage-3 oocytes. 

 Mean total length was 420 mm and mean ovary-free weight of the females was 868 g. 

 Fish were taken November-December 1988 along the Oregon coastline. 



