Baelde Biology and dynamics of reproduction in Hyperoglyphe antarctica 



207 



Slage 3 



60 1 200 400 600 800 1000 1200 1400 



Early stage 4 



30 

 20 



li) 



15 

 10 



5 



15 



5 io 



1— 



0. 5 



15 

 10 

 5 



III 



M..... J\\l\k.. 



Stage 4 



Early stage 4 



200 400 600 800 1000 1200 1400 

 I " Early stage 4 



200 400 Mill K00 1000 1200 1400 

 lilt.. Stage 4 



...J 



....4 



Stage 4 



n.. 



200 400 WKI 800 1000 1200 1400 



Stage 5 



Stage 6 



.  .llHl 



200 400 hOO SIM I 1000 I2IKI 1400 

 J |, III Stage 4* 



200 400 6(X) 800 1000 1200 1400 

 Oocyte diameter (Jim) 



Figure 7 



Frequency distribution of oocyte diameter by stage of 

 maturity (measurements from several ovaries pooled 

 in each graph ) for blue-eye trevalla, Hyperoglyphe ant- 

 arctica. White and black bars represent independent 

 measurements of unyolked and yolked oocytes, respec- 

 tively (unyolked oocytes were not measured in stage- 

 4 ovaries from graph E). * = partially spent ovaries. 



of yolked oocytes in stage-4 and stage-5 ovaries (Fig. 

 7, E-H). The fecundity (F) ranged from 1.3 to 11.0 

 million oocytes per fish, and although varying con- 

 siderably at given length (Fig. 8), it showed a sig- 

 nificant exponential increase with the length (FL) of 

 females, following the equation 



F = 4.2xKT 8 xFL 422 , 



where F is in millions and FL in cm. The linear re- 

 gression between log-transformed data was statisti- 

 cally significant: F=110.6, df=82; P<0.001, i? 2 =0.57. 

 Multiple regression analysis showed that the variation 

 in average diameter of yolked oocytes between mature 

 females (as illustrated in Fig. 7, E-H) did not affect 

 fecundity estimates (Table 4). The average relative fe- 

 cundity was 480 oocytes ( ± 125 SD ) per g ( gutted weight ) 

 and did not show clear trends with the size offish. 



Batch fecundity estimated for ripe females ranged 

 from 0.5 to 2.4 million oocytes (n=8) and also in- 

 creased with length (Fig. 9). The number of yolked 

 oocytes left in partially spent ovaries ranged from 

 0.6 to 7.9 million (Fig. 8), with a median value at 2.4 

 million (n=24). 



Spawning aggregation 



The bulk of the commercial catch for blue-eye trevalla 

 consisted of small (<55 cm FL), immature fish year 



10- 



Stages 4 + 5 

 Stages 4* + 5* 



60 



65 71) 75 



80 85 90 95 



Fork length (cm) 



Figure 8 



Annual fecundity estimates (black dots I and power rela- 

 tionship between annual fecundity and size of females (line 

 drawn from equation F = 4.2 x 10" 8 x FL 422 ) for blue-eye 

 trevalla, Hyperoglyphe antarctica. Fecundity estimated for 

 partially spent ovaries is also shown (white dots) but was 

 not included in the regression analysis. 



