204 



Fishery Bulletin 94(2), 1996 



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Figure 3 



Histological sections of the ovary of blue-eye trevalla, Hypcroglyphe antartica. 1A1 Histological section of ovary at 

 stage 7 showing type-1 postovulatory follicles. IB) Histological section showing two yolked oocytes at early alpha- 

 stage atresia (a) and a healthy yolked oocyte (y). (C) and (D) show whole preserved oocytes. (C) shows an oocyte at 

 alpha-stage of atresia (a), stage-4 yolked oocytes <y), a stage-5 oocyte iml (yolked plates only faintly visible in this 

 photo I. and a hydrating oocyte (h) with oil droplet. (D) shows postovulatory follicles Ipof) of type 1 and yolked 

 oocytes at an early stage of atresia (a). 



only ovaries in which hydrated oocytes formed a well- 

 defined mode were used. Also, the number of yolked 

 oocytes remaining in partially spent ovaries was de- 

 termined for 24 females. 



Results 



Gonad maturation 



Ovaries at stages 1 and 2 could not be distinguished 

 accurately by macroscopic examination and were 

 grouped together in the analyses, as were stages 7 

 and 8. GSI values varied greatly within maturity 

 stages (Table 2) and could not be used alone to as- 

 sess the development of ovaries. Macroscopic stag- 

 ing of the testes was more difficult than that for the 

 ovaries (Table 1). The main criterion used to assess 

 male maturity development, based on the presence 

 or absence of milt, was not consistent. As already 



observed by Horn and Massey ( 1989) in New Zealand, 

 milt was sometimes present in small, developing tes- 

 tes but absent in large testes. 



Histological examination of stage-4 ovaries led to 

 the distinction, within this stage, of ovaries at an 

 early stage of yolk formation. These ovaries were 

 characterized by a great variation in the size of oo- 

 cytes (Fig. 2D) compared with the uniform size of 

 fully yolked oocytes. They will be referred to as "early 

 stage 4" in the text. Partially spent ovaries (i.e. stage- 

 4 or stage-5 ovaries containing postovulatory follicles 

 and which were not identifiable macroscopically i will 

 be referred to as stages 4' and 5 . 



Spawning location and season 



Mature fish of both sexes (stages 4-6 for females and 

 stages 3-4 for males) were caught mostly off the 

 northeast coast of Tasmania, at about 41"S (Fig. 1), 

 but a few were occasionally caught in other areas. 



