230 



Fishery Bulletin 91(2), 1993 



unyolked 



yolked 



□ 



ripe 



100 



S> 



>. 

 c 



To 





« 



ra 

 c 

 o 



CD 

 > 



<D 



tr 



150 — i 



100- 



Figure 6 



Mean relative gonadal index, 95% confidence limits and range, and proportion of female 

 Lutjanus vittus at each maturity stage determined by whole-oocyte staging plotted against 

 the mean date of each sampling period. Number in each sample is shown. 



ing on the previous afternoon. In either case, the 

 late stage appears to persist for about 24 h. Only 13% 

 of fish examined from this subset did not have 

 postovulatory follicles, and most of these (74%) were 

 from fish sampled between 09:00 and 15:00 h. This 

 would be consistent with the hypotheses that follicles 

 persist for 24 h or less and that most fish spawn daily 

 during the major periods of spawning activity. 



The diel pattern of spawning indicated by data col- 

 lected in November-December 1982 was supported by 

 further sampling every 4h over 6-9 October 1988. The 

 proportions of ripe fish in samples taken at different 

 times throughout the day were significantly different 

 (likelihood ratio x 2 =110, df 6, p<0.001). Ripe fish were 

 found between 12:00 and 16:00 h (Fig. 10). The tempo- 

 ral distribution of MOD followed the same pattern ob- 

 served in November-December 1982. 



Spawning frequency 



As postovulatory follicles in L. 

 vittus persist for -24 h, they pro- 

 vide a good indication of spawn- 

 ing over the previous 24 h and 

 can be used to determine spawn- 

 ing frequency. Parameter A from 

 Eq. 2 provides an estimate of the 

 proportion of females spawning 

 each day averaged over the 29 d 

 lunar cycle. On average, females 

 spawn 21.7 times each lunar 

 cycle (95%CL=19.3-23.9). If we 

 assume that this spawning inten- 

 sity occurs during October-April, 

 then females spawn at least 150 

 times each year. 



Batch fecundity 



In order to determine the most 

 appropriate sites in the ovary 

 from which to take subsamples 

 to determine batch fecundity, the 

 number of eggs/mg tissue was 

 determined for six regions of the 

 ovary of five fish. Wedges of ovary 

 were taken from both inner and 

 outer walls at anterior, middle, 

 and posterior parts of each right- 

 hand ovary. There were no sig- 

 nificant differences in numbers 

 of eggs between inside and out- 

 side (ANOVA, F=0.016, df 1,4, 

 p=0.91) or anterior, middle, or 

 center (ANOVA, F=1.45, df 2,8, 

 p=0.29) nor any interaction between the effects (ANOVA, 

 F=0.54, df 2,8, p=0.60). A paired *-test indicated that 

 egg counts from a wedge of tissue taken from the middle- 

 outside position did not differ significantly between left 

 and right ovaries U=-0.008, df 4, p=0.99). Subsequently, 

 batch fecundity was estimated from the mean of three 

 subsamples taken from the anterior, middle, and poste- 

 rior of either the left or right ovary of 29 fish. The 

 coefficient of variation for estimates from three 

 subsamples was 0.02-0.21, with a mean of 0.11. 



The relation between fish length (L, mm) and batch 

 fecundity (F) was best described by the equation 



F = 3.656 x 10- 6 L , ° 91 (F=26.1, 



dfl,27,p<0.001), (Fig. 11) 



and the relation between fish total weight (W, g) and 

 batch fecundity by the equation 



