NOTE Tserpes and Tsimenides: Determination of age and growth of Xiphias gladius 



597 



 Aged animals (n = 1 , 1 00) 



Total no. of animals (n=l,325) 



61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 



LJFL in groups of 10 cm interval 



Figure 2 



Length-frequency distribution of sv/ordfish, Xiphias gladius, from the eastern Medi- 

 terranean indicating the total number offish and the number of those with readable 

 spines (aged animals). LJFL = lower-jaw fork length, n = sample size. 



lus is formed from middle spring to early summer 

 for all ages examined (Fig. 3). 



Parameters of the standard von Bertalanffy growth 

 function and the generalized model were computed 

 for males, females, and sexes combined (Tables 2). 

 Both models provided a good fit to the data (Fig. 4). 

 Results of the ARSS revealed that growth differences 

 between sexes were always highly significant 

 (F=8.22, P<0.001 for the standard growth function; 

 F=7.41, P<0.001 for the generalized model). 



The intercept values used in the proportional for- 

 mula of back calculation were obtained from the lin- 

 ear regression of LJFL on spine radius: 



LJFL = 59.09 

 LJFL = 62.43 

 LJFL = 61.45 

 combined], 



+ 18.32(S) [r 2 =0.98 for males]; 



+ 17.02(S) [r 2 =0.98 for females]; and 



+ 17.39(S) [r 2 =0.98 for both sexes 



where LJFL = lower-jaw fork length (cm); 



S = anal-fin spine radius (mm); and 

 r 2 = coefficient of determination. 



Males and females had significantly different slopes 

 CF=44.85,P<0.001). 



The constant b used for the nonlinear method of 

 back calculation was obtained from the slope values 

 of the relation between LJFL and spine radius: 



ln(LJPL) = 4.30 + 0.43(lnS) [r 2 =0.94 for males]; 

 IniLJFL) = 4.30 + 0.44(lnS) [^=0.96 for females]; and 

 IniLJFL) = 4.30 + 0.44(lnS) [r 2 =0.96 for both sexes 

 combined]. 



The slope of the relationship differed significantly 

 between males and females (F=6.33, P=0.01). 



The statistically significant differences between 

 the sexes for the LJFL spine-radius relation are likely 



