10 



Fishery Bulletin 92(1), 1994 



Table 4 



Mean hepatosomatic index (HSI: %), visceral fat index (Fat) and condi- 

 tion (K: dry weight/length 3 ) of Amblygaster sirm, Herklotsichthys 

 uadrimaculatus and Spratelloides delicatulus at different stages of gonadal 

 development (SE = standard error ± N = number of females examined). 



Species 



Stage 



HSI ± SE 



Fat ± SE tf(xlO-6)+SE N 



A. sirm 



maturing 0.38 ± 0.06 



ripe 0.43 ± 0.04 



spawning 0.39 ± 0.06 



spent 0.42 ± 0.05 



H. quadrimaculatus 



maturing 

 ripe 



spawning 

 spent 



0.87 ± 0.08 

 0.96 ± 0.06 

 1.04 ± 0.07 

 0.69 ± 0.04 



S. delicatulus 



maturing 1.41 ± 0.19 



ripe 1.98 + 0.10 



spawning 1.84 ± 0.15 



spent 1.46 ± 0.10 



3.4 ± 0.6 



3.2 ± 0.3 



2.6 ± 0.4 



1.7 ± 0.2 



1.4 ± 0.1 



1.6 ± 0.1 



1.8 ± 0.1 



1.7 ± 0.1 



1.3 ± 0.2 

 1.6 ± 0.1 

 1 3 • n 1 

 1.2 ± 0.1 



4.05 ± 0.25 

 4.14 ± 0.07 

 4.03 ± 0.13 

 2.77 ± 0.13 



;!ii 



16 



6 



3.89 ± 0.05 45 



3.81 + 0.05 127 



3.91 ± 0.05 95 



3.53 ± 0.06 40 



2.36 ± 0.06 

 2.51 ± 0.04 

 2.46 ± 0.04 

 2.28 ± 0.04 



15 

 41 

 35 

 55 



higher lifetime egg production 

 at all sites than did co-occur- 

 ring S. delicatulus. The num- 

 ber of days between successive 

 spawnings influenced esti- 

 mates of lifetime egg produc- 

 tion. Although longer in A. 

 sirm, the difference was not 

 significant (Table 8). 



quadrimaculatus, females dominated among fish 

 over 80 mm (Fig. 6). 



Egg production The number of spawnings per 

 month and the daily egg production of all species 

 generally followed the pattern of the proportion 

 spawning (Fig. 7). We found lower daily egg produc- 

 tion in A. sirm than in the other species. During the 

 period of maximum spawning activity, A. sirm and 

 H. quadrimaculatus spawned up to 20 times per 

 month (Fig. 7), and S. delicatulus spawned daily. 



Reproductive life span The reproductive life span 

 of A. sirm was significantly longer in Tarawa (60.1 

 + 15.4 days) than at the other sites during 1989-90 

 (P<0.01; Table 8). Similarly, we found H. 

 quadrimaculatus had a longer reproductive life span 

 at Abemama (141.8 ± 30.9 days) than at other sites 

 during 1989-91 (P<0.01; Table 8). During the same 

 period, the reproductive life span of S. delicatulus 

 was similar at all sites (57.5 ± 4.6 days). However, 

 the reproductive life span of S. delicatulus at 

 Tarawa varied significantly between years; fish 

 caught during 1990-91 were not as old as those in 

 previous j'ears (P<0.05; Table 8). No corresponding 

 pattern was observed in H. quadrimaculatus from 

 Tarawa. Herklotsichthys quadrimaculatus and S. 

 delicatulus lived significantly longer after maturity 

 than A. sirm (P<0.01). 



Our estimates of maximum lifetime egg produc- 

 tion of A. sirm were similar at the two sites (Abaiang 

 and Tarawa). Herklotsichthys quadrimaculatus had 



Recruitment Amblygaster 

 sirm recruited from a single 

 protracted period in Kiribati 

 during 1989 (March to October; 

 Fig. 8). We found a greater pro- 

 portion of survivors had been 

 born between March and July 

 than in all other months except 

 September (P<0.05). There 

 were insufficient data to com- 

 pare monthly egg production 

 with recruitment, but the pe- 

 riod of highest recruitment corresponded with the 

 times of greatest spawning activity. However, this 

 did not appear to be directly related to the absolute 

 number of oocytes produced (Fig. 7). 



The proportion of H. quadrimaculatus born each 

 month differed over the four years (P<0.05; Fig. 9). 

 In 1976, the greater proportion were born from 

 November to March, while in 1983 over 40% were 

 born during July. Fish caught during 1989-90 

 showed a different pattern. The highest proportion 

 in 1989 were born in May, whereas in 1990 the high- 

 est proportion were born in January. Over all 4 

 years' data, December ( 15.4% ) and July ( 13.7% ) had 

 the greatest mean proportion of births (P<0.05), but 

 the July value may be biased by the large value in 

 1983 (Fig. 10). Where data were comparable, we 

 found no relationship between proportion of annual 

 recruitment and monthly egg production (r.=0.70, 

 P<0.10, N=6 in 1989; r s =-0.15, P>0.5, N=U in 

 1990). 



The proportion of S. delicatulus born each month 

 varied considerably among the four years examined 

 (Fig. 10). December had the highest proportion of 

 births in 1976. In 1983, most fish were born between 

 May and August, and a similar pattern was found 

 in 1989. By comparison, the distribution of 

 birthdates was more evenly spread in 1990 (Fig. 10). 

 The months with the largest mean proportion across 

 the four years were May (11.2%), June (14.9%), July 

 (15.8%), and December (11.9%). We found a nega- 

 tive relationship between the proportion of births 

 and egg production in 1990 (r s =-0.58; P<0.05, 

 7V=10). 



