Watanabe and Yatsu: Interannual variation in length at age of Scomber /aponicus 



201 



32 



E 

 3 29 



26 -- 



23 



15 



H h 



20 25 



FL at age (cm) 



38 



36 



S. 34 



IB 



32 -■ 



30 



B 



15 



H — H 



H — i- 



20 25 



FL at age (cm) 



20 25 



FL at age (cm) 



Figure 4 



Scatter plots of FL at age 1 (A), age 3 (Bl and age 4 (C) on FL at age for chub mackerel (Scomber japonicus). Correlations between 

 FL at age 1 with age (r=0.83. n=28, actual sample size n'=8, df=6), age 3 with age (r=0.62, ;i=26. n =11. df =9) and age 4 with 

 age (r=0.67, u=24, n'=10) were all significant at P < 0.05. 



Table 2 



Correlation of FL at age and growth increment after age 

 0. n = actual sample size, n* and degree of freedom (df) 

 show the effective ;? and df when the data were corrected 

 for autocorrelation (Pyper and Peterman, 1998). Signifi- 

 cance level: **, P<0.01. 



Growth increment 



Ages 0-1 

 Ages 0-2 

 Ages 0-3 

 Ages 0-4 

 Ages 0-5 



df 



Correlation between FL and SST 



Growth in the first six months of life was correlated with 

 SST. We detected significant negative correlation between 

 FL-at-age and SST between April and June in the waters 

 bounded by 38-40°N and 141-143°E U--0.45, r 2 =0.20, 

 n=28, n =27, df=25, P<0.05, Fig. 5). The SST between July 

 and September of this area was also negatively correlated 

 with FL at age although the correlation coefficient was 

 not significant at 5% level. 



Growth analysis 



Model 1 that incorporated SST ( T) and population density 

 (D) gave a minimum Akaike's information criterion (AIC) 

 of 457.68 (Table 5) and the model was expressed by 



L- = 43.98 1 - exp( -2.585 )exp 



-5X 



:0. 271-0. 008T -0.2LD, 



(17) 



(18) 



Table 4 



Correlation between natural logarithm of total biomass 

 and mean FL for each age. n = actual sample size, n* and 

 dgree of freedom ( df ) show the effective n and df when the 

 data were corrected for autocorrelation (Pyper and Peter- 

 man, 1998). No correlations were significant (P>0.05). 



Age 



df 



This model estimated the FL at ages 0-5 well (Fig. 6). 

 The AIC of model 1 incorporating T and D was smaller than 

 the AIC of model 2; therefore the environmental factors had 

 an affect on k rather than L T . 



