20 



Fishery Bulletin 102(1) 



± 0.02 



£ 0.01 



rr 



D 



5 



4 

 3 " 

 2 " 



1 " 





 fc- 



^ > 



Mode (estimated by model 4.1) 



90% confidence interval (estimated by 



model 4.1) 

 ° Mode (sample) 



Date 



Figure 3 



Environmental fluctuations and prediction of the growth oiCorbiculajapon- 

 ica juveniles spawned in 1997 in Lake Abashiri by the best model (Model 4.1 

 in Tablel). (Al Insignificant environmental factors (factors excluded in the 

 model selection), turbidity (equivalent to kaolin density, ppmi and salinity 

 (psu, practical salinity unitl. (Bl Significant environmental factors (factors 

 included in the model selection I, temperature (°C) and water fluorescence 

 (equivalent to uranin density, /'g/L>. (Cl Daily relative increase rate of loca- 

 tion parameter (dRIRLl and daily relative increase rate of scale parameter 

 (dRIRS) estimated by the model. (Di Growth of Corbicula japonica; verti- 

 cal bars represent 90% confidence intervals for the shell lengths of the 

 samples. 



length distribution becomes asymmetric during growth, 

 skcwness of the distribution would increase according 

 to growth. However, there is no correlation between the 

 skewness and the means of the shell lengths. Therefore, we 

 thought that the shell length distribution of the cohort was 

 already asymmetric just after settlement. Such a distribu- 



tion might be influenced by fluctuations in larval settle- 

 ment during the spawning season; and larval settlement 

 would be influenced by fluctuations in larval supply from 

 the water column. During the spawning season of 1997. 

 the average planktonic larval density gradually increased 

 from 26 ind/m 3 on 25 July to a maximum of 603 ind/m 3 on 



