Sho|i and Tanaka: Feeding and growth of Scomberomorus niphonius 



377 



June 



20-23 



1995 



12 /m 2 



Figure 7 



Horizontal distribution of clupeid larvae in the Sea of Hiuehi during the three cruises in 1995 

 and in 1996. 



of Hiuehi where clupeid larva concentration was high 

 in late May. We suggest that spawning of S. niphonius 

 in the northern part of the Sea of Hiuehi would enable 

 their first-feeding larvae to meet high prey abundance 

 in the southern part. 



Significance of high ichthyoplankton prey 



Water temperature and prey concentration would be 

 possible factors that can influence growth rates of S. 

 niphonius larvae. In aquaria, the mean absolute growth 

 rate of S. niphonius larvae fluctuated between 0.87 and 

 1.28 mm/d depending on temperature between 18.2° and 

 22.6°C (Fukunaga et al., 1982; Shoji et al., 2001). In 

 the present study, the mean surface temperature of the 

 Sea of Hiuehi in late May was slightly higher in 1996, 

 although the difference was not significant. 



The higher abundance of clupeid larvae in 1995 would 

 better explain the higher larval growth rate in 1995. 

 The mean larval growth rate in late May 1995, 1.05 

 mm/d, approximates those reported in aquaria at the 

 same temperature (1.03 mm/d at 20.8°C; Fukunaga et 

 al., 1982) where S. niphonius larvae were provided with 

 an excess of prey, indicating that the prey concentration 

 in late May 1995 met larval requirements. It is likely 

 that the lower growth rate in late May 1996 resulted 

 from lower prey concentration. This conclusion is sup- 

 ported by results of the stomach content analysis: the 

 larval feeding incidence was significantly lower in May 

 1996. We conclude that clupeid larvae concentration 

 had a significant effect on growth of the S. niphonius 

 larvae. 



In the Sea of Hiuehi, clupeid larvae abundance greatly 

 increased from April to May. We suggest that the prey 



