206 



Fishery Bulletin 94(2). 1996 



Fork length (cm) 

 Figure 5 



Relative abundance of mature individuals of blue-eye trevalla, 

 Hyperoglyphe antarctica (stages 4-6 for females, stages 3-4 for males) 

 by 1-cm size intervals. Data were fitted to the logistic equation shown in 

 text. Black dots represent females; white dots represent males; and n = 

 sample size. 



ovaries were of two types. The first type consisted of 

 small ovaries with abundant white oocytes visible 

 macroscopically within a translucent, pinkish mass 

 of unyolked oocytes. Histological examination later 

 revealed that the white oocytes were oocytes at an 

 early stage of yolk formation and were undergoing atre- 

 sia. This type of ovary was observed in May and June 

 1992 and 1993, and represented 64% of all yolked ova- 

 ries examined during these periods. It was always ob- 

 served in preadult females at size below the average 

 size at maturity (mean FL=63.6 cm [±3.2 cm SD1). 



Only two females presented the second type of 

 atretic ovaries; they had large ovaries (GSI of 6.9 

 and 8. 1 ) and nearly all fully yolked oocytes 

 were at an early stage of atresia. These 

 atretic oocytes could not be detected mac- 

 roscopically, but they were recognizable 

 microscopically in preserved samples ( Fig. 

 3, C and D). The two females were caught 

 during the spawning period in March 1993; 

 they represented only 1.2% of all mature 

 ovaries examined histologically. 



Occurrence of postovulatory 

 follicles 



postovulatory follicles were found in hy- 

 drating ovaries (stage 5*) (Fig. 6). 



Measurement of whole oocytes 



As maturation progressed, a clear gap 

 appeared between unyolked and yolked 

 oocytes (Fig. 7, A-D), showing that the 

 fecundity of blue-eye trevalla is determi- 

 nate. The recruitment of oocytes from the 

 reserve of unyolked oocytes was com- 

 pleted when the average diameter of 

 yolked oocytes reached about 650 /jm 

 (Fig. 7E). Unyolked oocytes present in 

 these ovaries were at stage 2 and had a 

 diameter of less than 100 /tm (the gap in 

 size between unyolked and yolked oo- 

 cytes was clear and unyolked oocytes 

 were no longer measured in most ad- 

 vanced ovaries). The diameter of yolked 

 oocytes then increased slightly to about 

 700 f.im (Fig. 7G) before migration of the 

 nucleus and hydration began (Fig. 7. H- 

 I). After a batch was spawned, formation of a new 

 batch began from the remaining pool of yolked oo- 

 cytes, showing migration of nucleus and hydration 

 (Fig. 7, J-K). The mean oocyte diameter of stage-4 

 ovaries used to construct graphs E to G ranged from 

 500 to 770 ^m (having an overall mean of 640 [±60 

 SD] /.im, n=8l). Hydrating oocytes observed during 

 the present study were about 1.3 mm (Fig. 71). 



Fecundity 



Because fecundity was found to be determinate, an- 

 nual fecundity was estimated from the standing stock 



Postovulatory follicles were found in 16.8% 

 of all mature ovaries examined (n=167). 

 They were never found in ovaries at early 

 stage of yolk formation. Both type-1 and 

 type-2 postovulatory follicles were usually 

 present in stage 4*, whereas only type-2 



2100 



follicle perimeter ( um ) 



Figure 6 



Frequency distributions of the perimeter imicrometersi of type-1 and 

 type-2 postovulatory follicles (pooling of measurements from 16 ova- 

 ries) for blue-eye trevalla, Hyperoglyphe antarctica. 



