862 



Fishery Bulletin 97(4), 1999 



and comparative morphometries; Ibanez-Aguirre and 

 Gallardo-Cabello (1996a) on total and natural mor- 

 tality and Sanchez-Rueda et al. ( 1997 ) on the analy- 

 sis of sediments in stomach contents. On the inter- 

 national scene, the studies on M. cephalus by de Silva 

 ( 1980 ), Perera and de Silva ( 1978 1, de Silva and Silva 

 (19791 in a coastal lagoon in Sri Lanka, Drake et al. 

 (1984) in the coastal lagoon of San Fernando Cadiz, 

 Cech and Wohlschlag ( 1975) along the coast of Texas, 

 Broadhead (1958) along the coast of Florida, and 

 Thompson (1963) in Australia, are worthy of men- 

 tion, as well as those carried out by Alvarez (1976, 

 1979 and 1981), Richards and Castagna (1976). and 

 Philhps et al. ( 1987 ) on M. curema . 



In view of the above studies, the purpose of this 

 study was to carry out an in-depth analysis of the 

 growth characteristics of M. cephalus and M. curema 

 with respect to length, sex, weight, and longevity in 

 Tamiahua lagoon, Veracruz, Mexico. 



Material and methods 



Specimens were obtained from the commercial catch 

 landed near Tamiahua lagoon, Veracruz, Mexico ( Fig. 

 1). The most commonly employed fishing nets were 

 gill nets of 35-mm mesh size (knot-to-knot) for M. 



9800' 



nlet of Tampachiche 



/ 



Gulf of 

 Mexico 



40'  



Veracruz State 



20" 



Inlet of Corazones 

 Old Inlet 



2rOO" 



cephalus and 30-mm mesh size (knot-to-knot) for M. 

 curema . Sampling was carried out monthly during 

 the first 8 days of each month for a year, from April 

 1991 to March 1992. 



Total length (TL) was recorded from 2628 speci- 

 mens of M. cephalus and 3354 of M. curema . For the 

 study of growth, two independent readers examined 

 scales, and otoliths (right sagitta) from 232 speci- 

 mens of M. cephalus (122 females and 110 males) 

 ranging from 200 to 400 mm and 292 specimens of 

 M. curema ( 148 females and 144 males) ranging from 

 180 to 330 mm. The scales were cleaned, placed be- 

 tween two glass slides, and observed with transmit- 

 ted light. The otoliths were submerged in a petri plate 

 in xylol as a clarifying liquid and observed through 

 a stereoscopic microscope with transmitted light. The 

 analysis of the annual frequency variation of the fast 

 growth rings (opaque) and slow growth rings (hya- 

 line) of the margin of the otoliths showed that each 

 year, one fast growth band and one slow growth band 

 are deposited in the otoliths of boths species of mul- 

 lets (Ibanez-Aguirre and Gallardo-Cabello, 1996b). 

 It was reported earlier that otoliths give better re- 

 sults than do scales for the age determination of both 

 species and make possible a definition of five age 

 groupsfovM. cephalus and sixfor M. curema (Ibanez- 

 Aguirre and Gallardo-Cabello, 1996b). These aver- 

 age lengths were used to obtain the constants for the 

 von Bertalanffy equation (Table 1). 



Ages "0" and "1" were not collected for M. cephalus, 

 as a result of the mesh size of the nets; instead they 

 were obtained by using the back-calculation method 

 ofLea(1910, in Francis, 1990) and Bagenal andTesch 

 (1978, in Francis, 1990). 



The constants for the von Bertalanffy equation 

 ( 1938), L^^, k , and /„, were obtained by using the com- 

 bmed method of Ford ( 1933 ) and Walford ( 1946), and 

 the methods of Gulland (1964), Tomlinson and 

 Abramson (1961), Allen (1966), Beverton^, Pragei 

 ( 1987 ), and Bayley ( 1977 ). Growth was also measured 

 for each sex of both species. Growth curves for both 

 species were obtained from the constants of the equa- 

 tion calculated by the above mentioned methods. The 

 sum of the squared differences (Ze,'^) was used to 

 compare the differences between calculated and ob- 

 sei"ved values. 



Hotelling's T' test (Bernard, 1981) was used to 

 compare growth curves of the two sexes of both spe- 

 cies. This test assumes that estimations ofL. , k, and 

 /„ for both groups were obtained from two normal 



Figure 1 



Map of the Tamiahua Lagoon, Veracruz, Mexico. 



' Beverton, R. J. H. 19.54. Notes on the use of theoretical mod- 

 els in the study of the dynamics of exploited fish populations. 

 U.S. Fish Wildl. Serv., Fisheries Laboratory, Beaufort. Misc. 

 ("ontrib. Rep., 181 p. 



