Milton et al.: Reproductive biology and egg production of three species of Clupeidae 



109 



o 



o 



5 



4 



(5 3 



2 

 1 



i~+i 



~i — i — i — i — r 



B 



J 



-\ — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i i i 



1.5 -, 



j'f'm'a'm'j'j'a's'o'n'd 



1989 



j'F m a'm'j'j'a's'o' 



1990 



Figure 2 



Monthly variation (±95% confidence limits) in (A) 

 condition, (B) visceral fat index, (C) hepatosomatic 

 index and (D) proportion spawning of female 

 Amblygaster sirm from Kiribati between January 

 1989 and October 1990. 



5-i 



£ 4 



o 3 



H 



Ny*** 



V****V 



1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 



4 -i 

 3 



CO O - 



1 







B 



&*k K/V^V 



I I I I 1 1 I I I I 1 I I 1 I I I 1 I I I 



rn n I r~\ r~ 



* 2 -\ 

 £ H 



#-****^ 



i i 1 1 i i i i i i i i i i 1 1 i i i i i i i i i i 1 1 i i 



100 



Figure 3 



Monthly variation (±95% confidence limits) in (A) 

 condition, (B) visceral fat index, (C) hepatosomatic 

 index and (D) proportion spawning of female 

 Herklotsichthys quadrimaculatus from Kiribati be- 

 tween November 1988 and April 1991. 



higher at Butaritari (1.41 ± 0.06; N=57) than at 

 other sites (Abaiang HSI=1.07 ± 0.11; N=7; Tarawa 

 HSI=0.81 ± 0.09; A/=14). The proportion of male S. 

 delicatulus that had GSI greater than 5% was also 

 higher at Butaritari (36%) than at other sites 

 (Abaiang 17.5%; Tarawa 20%). 



Oocyte weights of A. sirm and S. delicatulus dif- 

 fered significantly from site to site (Table 7). In S. 

 delicatulus, we found the greatest oocyte weight at 

 Abemama and Abaiang — significantly higher than 

 at Butaritari and Tarawa (P<0.01). Oocyte weights 

 in A. sirm were also higher at Abaiang (P<0.001; 



Table 7). We found no significant differences among 

 sites for oocyte weights of H. quadrimaculatus. 



Sex ratio The sex-ratio of A. sirm, H. quadrima- 

 culatus, and S. delicatulus changed as fish grew but 

 only among the largest length classes of each spe- 

 cies were there significant deviations from a ratio 

 of 1:1. In all three species, females dominate the 

 largest length classes (Fig. 6). In our samples, we 

 found significantly more female A. sirm and S. 

 delicatulus among fish larger than the length at first 

 spawning (180 and 45 mm respectively). With H. 



