Ibaiiez Aguirre et al.: Growth analysis of Mugi/ cepha/us and M. curema 



867 



Finally, it is important to take into account that 

 differences between growth rates are important even 

 in areas that are very close; these differences could 

 be explained by the different methods applied for age 

 determination (Oren, 1981); however, these differ- 

 ences could be also explained by the world-wide dis- 

 tribution of this species and its different survival 

 strategies. On the other hand, the differences be- 

 tween growth rates can also occur because of com- 

 mercial exploitation, for when fishing is very intense, 

 the commercial size offish decreases and the varia- 

 tions of the k coefficient increase. 



The values of the parameters of the von Bertalanffy 

 growth equation for M. curema in different areas are 

 shown in Table 7. In our paper, the value of/? calcu- 

 lated for M. curema shows a higher position in rela- 

 tion to the value proposed by Alvarez ( 1979) and the 

 value of L^_, is higher in Cuba. On the other hand, the 



values of A' obtained by Richards and Castagna ( 1976) 

 in Virginia and by Phillips et al. (1987) in theNicoya 

 Gulf of Costa Rica show a higher position in relation 

 to the k value obtained in our paper. 



For the relation of growth between sexes, some 

 authors have shown that there are no differences 

 between sexes: for M. cephalus, Dannevig (1902); 

 Kesteven (1942); Thomson (1951); Morovic (1957); 

 Erman ( 1959); Thakur ( 1967); Cech and Wohlschlage 

 (1975); Grant and Spain (1975); for M. curema, 

 Alvarez ( 1979) and Angell (1973). On the other hand, 

 Ezzat (1965), Brulhet (1974; 1975), and Farrugio 

 (1975) have stated that there are differences in the 

 growth between sexes. However, these latter authors 

 did not infer whether these differences in the growth 

 between sexes are significant or not from a statisti- 

 cal point of view. For this reason, a statistical test 

 to compare the growth curves between sexes was 



