Hunter et al,: Fecundity, spawning, and maturity of Microstomus paoficus 



1 17 



equal to or less than 0.86mm were included, but was 

 insignificant when only those having a diameter 

 greater than 0.86mm were considered. We concluded 

 that ovaries in which the advanced stock of yolked 

 oocytes has an average diameter of 0.85 mm or less are 

 not sufficiently developed to be certain that the annual 

 stock is fully recruited. Consequently, to estimate the 

 potential annual fecundity, we used only females in 

 which the average oocyte diameter of the advanced 

 stock exceeded 0.85 mm. 



No relationship between oocyte diameter and total 

 fecundity was detected in the females taken off cen- 

 tral California during November-December. Oocyte 

 diameter may not have been a significant variable in 

 central California because fewer females were exam- 

 ined and their ovaries were more advanced. In 48% of 

 females from California, advanced yolked oocytes 

 averaged more than 0.85mm in diameter {N 65), 

 whereas only 34% of the fish taken off Oregon had 

 oocytes that did so {N 128). 



Seasonal variation in total fecundity 



Total fecundity of Dover sole decreased during the 

 spawning season off both central California and Oregon 

 (Fig. 5). Analysis of covariance indicated that equations 

 expressing the relation between female weight and 



fecundity differed within the spawning season (Table 

 9). The total fecundity for a 1kg female declined from 

 about 80,000 advanced oocytes in December to about 

 50-60,000 during the spawning season (Table 9). 



To further describe the decline in total fecundity over 

 the season, we also regressed fecundity on female 

 weight and elapsed time since 1 November. In both cen- 

 tral California and Oregon the negative coefficients for 

 elapsed time were significant, indicating that total 

 fecundity declined wath elapsed time (Table 9). Analysis 

 of covariance indicated that multiple regression equa- 

 tions for California and Oregon were not different 

 (analysis over a similar weight range of 174-1542 g; 

 Fi 388 1.59, P 0.208; adjusted mean fecundity for 

 Oregon 57,849, SE 2092; adjusted mean fecundity for 

 California 54,733, SE 1152). When we combined data 

 for the two regions, we found that total fecundity 

 declined on the average about 12% per month. This 

 computation underestimated the actual rate of decline, 

 since it did not take into account females that had 

 spawned all of their advanced yolked oocytes. 



Potential annual fecundity 



Potential annual fecundity was considered to be equi- 

 valent to the standing stock of advanced yolked oocytes 

 in fully developed, prespawning females. We consider 



Table 9 



Linear regression coefficients, confidence intervals, and estimates for the relationship between female weight (W, ovary-free, in g) 

 and total fecundity (Yp ) of Dover sole Murostomus pacificus from California and Oregon. Analysis of covariance for the effect of season 

 on the relation between total fecundity and weight. Multiple regression coefficients are also given for the effect of elapsed time (T; 

 days since 1 Nov.) and female weight on total fecundity. 



State 



Mean date of 

 cruise 



Linear regression by month and state 



Linear equation Yp = a -h bW 



Regression 

 estimate for 



Analysis of covariance for 

 effect of month with 

 weight ranges similar 



95% CI b 95% CI r- 



N 1 kg female Variables df 



Oregon 



Central California 



7 Dec 88 

 3 Mar 89 



8 Dec 85 

 31 Jan 87 

 23 Mar 88 



17,640 ±15,460 65.5 ±16.4 

 14,492 ±8,530 42.9 ±10.6 



29,497 

 20,154 

 12,072 



±6,121 



±6,344 



±16,924 



51.6 

 38.9 

 40.7 



±16.1 



±6.8 



±18.6 



0.49 

 0.66 



0.58 

 0.42 

 0.15 



63.9 

 67.9 



42.9 



127.0 



18.9 



67 

 36 



31 

 173 

 103 



83,140 

 57,392 



81,097 

 59,022 

 52,772 



Weight 

 Month 

 Error 

 Total 



1 67.85 

 1 20.06 



95 



97 



Weight 1 25.20 



Month 2 18.91 



Error 217 



Total 220 



< 0.005 



< 0.005 



< 0.005 



< 0.005 



Multiple recession of total fecundity on weight and days elapsed since 1 November 



Multiple regression equation Yp = a + b, W -h bjT 



State 



a 95% CI bi 95% CI 



95% CI 



N 



W W T T 



min max ^ nun * max 



(g) (g) (d) (d) 



Oregon 35,162 



Central California 41,552 



±13,378 55.2 

 ±8,142 40.3 



±11.2 

 ±6.4 



-237 

 -224 



±104 

 ±63 



0.59 

 0.37 



74.9 

 92.3 



103 

 307 



147.7 

 120.0 



1815.9 

 1690.3 



33 



34 



151 

 160 



