Sun et a! : Age and growth of Xiphias glodius 



827 



The monthly means of marginal increment ratio, MIR, 

 for females with all ages combined, dropped drastically 

 from the maximum of 0.86 in June to the minimum of 0.32 

 in July and August ( Fig. 7 ). Similarly, the monthly means of 

 MIR value for males declined sharply from the maximum 

 of 0.65 in June to 0.37 and 0.35 in July and August. For 

 both females and males, the monthly means of MIR dur- 

 ing the period from September to March were not differ- 

 ent (ANOVA, P =0.95, P,=0.48), but the monthly means of 

 MIR in April, May, and June were significantly higher than 

 that in July or August, respectively (two sample /-tests, 

 P<0.001). Also, the mean MIR in August was significantly 

 lower than that in September (/-tests, P <0.001, P,<0.01). 

 The trends exhibited by monthly means of MIR for females 

 and males for ages 2 to 5, respectively, were the same as 

 those just described for all ages combined (Fig. 8). These 

 patterns indicated the formation of one ring per year dur- 

 ing the period from July to August. The MIR analysis by 

 age was not performed for age 1 and ages greater than 5 

 because the formula used to determine MIR does not apply 

 to samples less than or equal to age 1 and there was a lack 

 of a sufficient number of samples for ages greater than 5. 



The mean band radii, by band group for female and male, 

 are shown in Table 1. The observed LJFLs of female and 

 male swordfish were plotted against their corresponding 

 ray radii for method I and method II, respectively (Fig. 9). 

 The relationships between LJFL and ray radius are de- 

 scribed as follows: 



Method I Female: LJFL = 21. 137S -i- 65.091 



|r2=0.8894, «=3341; 



Male: LJFL = 19.966S -i- 68.160 



[r2=0.8737,n=2931. 



Method II Female: LJFL = 73.754S05i93 



[r2= 0.8753, ;!=334]; 

 Male: LJFL = 77.075S»-*"2 



|r-^=0.8742,«=2931. 



ANCOVA revealed significant differences in the rela- 

 tionship between the males and females for both methods 

 (for method I, P.,.,, ,,3.^=8.36, P<0.001; for method II, P.333 

 292 =15.59, P=0.004). The average back-calculated lengths- 

 at-age obtained using method I and method II are shown 

 in Table 2. Growth rates were higher during the first year 

 of age (mean 95.2 cm and 96.1 cm LJFL for males and 

 females, respectively, for method I, compared to 88.6 cm 

 and 90.4 cm LJFL for males and females, respectively, for 

 method II). After the first year of age, the growth rates of 

 both sexes slowed appreciably. Growth rates of females 

 were always higher than those of males, especially after 

 the age of three. Also, the growth rates were always higher 

 for method II than for method I except for the first year 

 of age. Fitted standard VB and generalized VE growth 



