FISHERY BULLETIN: VOL. 87, NO. 4, 1989 



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STAGE 



Figure 2. — Range in (A) uku and (B) onaga gonosomatic 

 index (GSI) for each developmental stage designation in 

 Table 1. 



From July to October, the mean GSI values 

 gradually decreased as spawning activity ta- 

 pered off. By November, all fish examined were 

 either partially or completely spawned (stage 

 IV). Stage IV fish were not found during the 

 spawning season. 



In contrast, female onaga began maturing in 

 June. Fully ripe onaga were not found until July, 

 and spawning activity did not peak until October 

 (Figs. 3, 4). The GSI values dropped sharply in 

 November as the incidence of completely 

 spawned and partially spawned individuals 

 abruptly increased. As with uku, completely 

 spawned individuals were not found until the 

 close of the spawning season. Mean monthly GSI 

 values for male onaga reflected a similar pattern. 



Size at Sexual Maturity 



Uku matured at a substantially smaller size 

 than onaga. Fifty percent of the female uku at- 

 tained sexual maturity at 425-475 mm FL, as 

 evidenced by elevated GSI's (Fig. 5) and by the 

 percentage of fish judged mature by visual stag- 

 ing (Table 2). By the time the fish reached the 



J FMAMJJASOND 

 MONTH 



Figure 3. — Monthly mean gonosomatic inde.x (GSI) for 

 female uku and onaga. Bars indicate 95% confidence limits. 

 Juvenile (<500 mm FL) uku and juvenile (<600 mm FL) 

 onaga were excluded from analysis. Sample size is indicated 

 next to each data point. 



Table 2. — Stage of maturity, compared by 50 mm fork length 

 (FL) size classes, for uku and onaga sampled during their 

 respective spawning seasons. 



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