Baelde Biology and dynamics of reproduction in Hyperoglyphe antarctica 



205 



Table 3 



Average size at maturity (FL 5 ) by sex, and 95 f /f confidence 

 limits for blue-eye trevalla, Hyperoglyphe antarctica. Data 

 were fitted to the logistic equation shown in text. Results 

 are shown for data collected during the current study and 

 for data collected in the mid 1950s before the fishery de- 

 veloped (from Cowper and Downie's unpubl. data). CL = 

 confidence limits. 



FL„ 5 95% CL 



Current data 

 Females 

 Males 



1803 

 1613 



-29 si, 

 -21.06 



Cowper and Downie's data 

 Females 813 -23.79 



Males 498 -24.05 



0.419 

 0.342 



0.341 

 0.397 



71.3 

 61.6 



(-ill 8 



60.6 



70.7-71.9 

 61.2-62.1 



69.2- 

 59.6- 



70.3 

 61.4 



Off northeast Tasmania, and over the 20-month sam- 

 pling period, mature fish were caught in small num- 

 bers between October and December; then then- 

 abundance increased markedly between January and 

 March (Fig. 4). Stage-4 females caught from October 

 to December 1992 were at early stage of yolk forma- 

 tion (early stage 4) with a low GSI ranging from 1.6 to 

 2.3. GSI values then increased to a mean of 5.6 (with a 

 standard deviation [SD] of ±2.3) in January, 8.0 (±2.9) 

 in February, and 9.4 (±2.7) in March, 1993. In both 1992 

 and 1993, ripe (stage-5) and partially spent (stage-4* 

 and stage-5*) females were caught from early March 

 to early May; females in postspawning condition ( stages 

 7 and 8) were caught from mid-March, their maxi- 



Month 

 I I Immature to early developing I I Developing 

 I Late developing to running ripe |^&j Spent and resting 



Figure 4 



Monthly proportions (as a percentage) of maturity stages 

 by sex for blue-eye trevalla, Hyperoglyphe antarctica. n = 

 sample size. 



mum abundance occurring in May and June (66.3% of 

 the total 445 postspawning females examined). Thus, 

 maturation of ovaries spanned several months, from 

 October to February, and actual spawning apparently 

 took place from early March to early May. 



Size at maturity 



The smallest mature female observed during the 

 present study was 59 cm FL, and the smallest ma- 

 ture male was 52 cm FL. The estimated average sizes 

 at maturity were 71.3 and 61.6 cm FL for females 

 and males, respectively (Table 3; Fig. 5). These sizes 

 were very similar to those estimated from data col- 

 lected in the mid 1950's (Table 3). 



Rate of atresia 



The rate of atresia for both unyolked and yolked oo- 

 cytes was generally low (atretic oocytes represented 

 between 1 and 10% of all oocytes when present). 

 However, a few ovaries presented a high level of atre- 

 sia ( about 90% ) of their yolked oocytes. These atretic 



