Ibaiiez Aguirre et al,; Growth analysis of Mugil cephalus and M. curema 



865 



Growth between sexes 



For M. cephalus. the growth curves that best fitted 

 observed data were obtained with the Prager method 

 (1987) and Beverton' equation (Table 2). In M. 

 cephalus females the value of L^, is higher than in 

 males, though the differencies between k values are 

 small. 



In M. curema the growth curves that best fitted 

 observed values were obtained with the Prager ( 1987 ) 

 method, as shown in Table 3. The k value in M. 

 curema males is higher than in females; therefore 

 males will reach L^ faster than females and the 

 growth curve will be slightly more convex. Con- 

 versely, the females, showed a slighter growth curve 

 and therefore greater longevity. However, in the case 

 of M. cephalus. the k value was obsei^ved to be the 

 opposite of that of M. curema . 



Table 4 contains the values of the parameters and 

 their variances calculated with the Prager method 

 (1987) for both species. The results from the multi- 

 variate analysis show that females and males of M. 

 cephalus and M. curema grow differently (Table 5). 

 The calculated value of T- ( 8928. 135 ) is considerably 

 higher than the tabulated value ( 11.796, P<0.01) for 

 M. cephalus and the same happens for M. curema , 

 with a calculated r-( 1843.808) and tabulated value 

 (11.777, P<0. 01). 



Growth in weight 



Length-weight relationship The relationships be- 

 tween length and weight stretch to be isometrical 

 (Figs. 3 and 4). In length-weight relationships, dis- 



persion is higher in M. cephalus because of the weight 

 of gonads and viscera. 



Theoretical growth in weight The theoretical weight 

 for M. cephalus and M. curema in relation to each 

 age group was obtained employing the mentioned 

 weight equations (Figs. 5 and 6). 



Longevity (Age A^g^) Both species reach the 95% 

 of L^^ at the following ages: 



Mugil cephalus 

 Aq 95 = 28.32 years 



Mugil curema 



^0 9.5 



= 18.68 years 



The 95% of L .^ is reached between sexes as follows: 



Mugil cephalus Mugil curema 



Females = 26.24 years Females = 19.17 years 

 Males = 26.46 years Males = 14.04 years 



Discussion 



The parameters of the von Bertalanffy growth equa- 

 tion for M. cephalus in different areas of the Gulf of 

 Mexico are shown in the Table 6. In the present pa- 

 per, the value of ^, calculated for M. cephalus is 

 smaller than values presented by Marquez ( 1974) and 

 Diaz and Hernandez ( 1980). Similarly, the values of 

 L given from these authors are smaller than those 

 obtained in our paper On the other hand, differences 

 of the growth parameters for the Texas coast (Cech 

 and Wohlschlag, 1975 ) and Florida ( Broadhead, 1958 1 

 are very pronounced in relationship to those obtained 

 in our paper: the L ., values are smaller. 



