1 14 



Fishery Bulletin 92(1), 1994 



100 110 120 130 140 150 160 170 180 190 200 >200 



Length (mm) 



100 



<30 40 50 60 70 80 90 >90 

 Length (mm) 



100 

 BO 

 60 - 



40 



20 - 



C 



<30 35 40 45 50 55 60 >60 

 Length (mm) 



Figure 6 



Ontogenetic change in the proportion female of (A) 

 Amblygaster sirm , (B) Herklotsichthys quad- 

 rimaculatus and (C) Spratelloides delicatulus (±95"7r 

 confidence limits) from Kiribati. 



peids is probably linked to cycles in prey abundance, 

 fat storage may reduce the effects of short-term fluc- 

 tuations in prey abundance on reproduction. 



Diel timing of spawning events was similar for all 

 species. We found new post-ovulatory follicles (day- 

 0) in females collected from 2130 hours onwards 

 with the greatest proportion detected after 0100. 

 This indicates that these species spawn during the 

 early part of the night, probably prior to midnight. 

 Our results are consistent with previous studies that 

 found high densities of A. sirm eggs in the plank- 

 ton after midnight (Delsman, 1926; Lazarus, 1987). 

 Studies of other sardines (Goldberg et al., 1984; 

 Isaac-Nahum et al., 1988; Re et al., 1988) and tropi- 



<o~ 5-, 

 o 



.* 4 



c 

 o 



D) 

 O) 



O , 



_>. 

 TO 



Q 



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



1989 



Avr 



j'f'm'a'm'jjVs'o' 



1990 



Time 



o n c i 



ND J FMAMJ J ASOND J FMAMJ J ASONCJj FMAM 



1989 



1990 



1991 



Time 



t"| i i i i i i i i i i i i n i i i i i n i I i i i ii 



ND J FMAMJ J ASOND J FMAMJ J ASOND J FMAM 



1989 



1990 



1991 



Time 



Figure 7 



Monthly estimates of daily egg production of (A) 

 Amblygaster sirm, (B) Herklotsichthys quadrima- 

 culatus and (C) Spratelloides delicatulus from 

 Kiribati during the study period. 



cal clupeoids (Clarke, 1987) also showed that spawn- 

 ing peaked before midnight. 



Length and age at sexual maturity of A. sirm and 

 H. quadrimaculatus in Kiribati differed from those 



