Milton et al.: Reproductive biology and egg production of three species of Clupeidae 107 



age) did not differ among fish 

 from the four sites. In Kiribati, 

 S. delicatulus become sexually 

 mature at 40 mm and two 

 months of age and spawn 

 shortly afterwards. Compared 

 to the other species, the length 

 and age at maturity and first 

 spawning varied less among 

 sites (Table 3). The three spe- 

 cies differed in the length and 

 age at sexual maturity and 

 first spawning. However, as a 

 proportion of their maxima, the 

 three species were similiar Cu- 

 test; P>0.1). All matured and 

 spawned at about 70% of maxi- 

 mum size and 50% of maxi- 

 mum age (Table 3). 



Timing of spawning We iden- 

 tified recent spawning by the presence of post-ovu- 

 latory follicles in the ovaries. In A. sirm, follicles 

 were detected in samples collected between 0100 to 

 1630 hours, and new post-ovulatory follicles (iden- 

 tified as day-0 [<24 hr]; Hunter and Goldberg, 1980; 

 Goldberg et al., 1984) were observed in fish collected 

 between 0100 and 0510 hours. Female H. 

 quadrimaculatus with post-ovulatory follicles were 

 collected between 2130 and 1630 hours and day-0 

 follicles were found in samples collected between 

 2130 to 0300 hours. In female H. quadrimaculatus 

 caught after 0300 hours, follicles could not be dis- 

 tinguished from day-1 type POF's, as the follicles de- 

 generated rapidly. Similarly, we detected post-ovu- 

 latory follicles in female S. delicatulus collected from 

 2210 to 1930 hours, and follicles of all females col- 

 lected earlier than 0845 hours were identified as 

 day-0. Those in females of the single sample col- 

 lected later in the day ( 1930) were assigned as day-1. 



Spawning season There was protracted spawning 

 in A. sirm with periods of intense spawning activ- 

 ity (Fig. 2). During both 1989 and 1990, fish 

 spawned August to October and also during May- 

 June in 1990. Condition, fat index, and HSI were 

 less during spawning periods and reached a peak in 

 March-April 1990, i.e., before spawning (Fig. 2). We 

 found less fat deposits in spent fish and the fish 

 were in poorer condition than fish with gonads in 

 other stages of development (P<0.05; Table 4). We 

 noted no significant differences in HSI among fish 

 with gonads at the same stage of development. 



Herklotsichthys quadrimaculatus spawned 

 throughout the study period: 20 to 50%> of the popu- 



lation spawned each month (Fig. 3). Female condi- 

 tion, fat index, and HSI all followed a similar pat- 

 tern during the study but did not appear to be di- 

 rectly related to spawning activity. Fish in spawn- 

 ing condition had the highest HSI, fat, and condi- 

 tion values, but these were only significantly greater 

 than those of spent fish (P<0.05; Table 4). 



Spratelloides delicatulus spawned almost continu- 

 ously throughout the study period but spawning 

 varied in intensity (Fig. 4). Peak spawning occurred 

 during different periods in each of the years 

 sampled. Female HSI and fat index showed a simi- 

 lar pattern during the study but monthly changes 

 in these parameters or fish condition did not follow 

 the spawning cycle. We found no significant differ- 

 ences in HSI or fat index for females with ovaries 

 in different stages of development (P>0.1; Table 4). 

 Fish condition was lower among spent fish than in 

 ripe or spawning fish (P<0.05; Table 4). Females 

 with ripe ovaries had higher mean HSI, fat, and 

 condition than those in other stages of development, 

 but these differences were not significant (Table 4). 



Fecundity The relative fecundity of A. sirm and H. 

 quadrimaculatus did not differ among sites or sea- 

 sonally within sites in Kiribati (ANCOVA with 

 weight as covariate; overall P>0.07; Table 5). How- 

 ever, the relative fecundity of H. quadrimaculatus 

 was significantly different between fish from Tarawa 

 and Abemama (<-test; P<0.05). Batch fecundity of both 

 species did not differ among sites in Kiribati. Within 

 their respective species groups, both species had simi- 

 lar batch fecundities to the other species listed, al- 

 though their relative fecundities were lower (Table 5). 



