Fishery Bulletin 89(1). 1991 



drum Pogonias cromis (January-April; Beckman et al. 

 1990a), and Atlantic croaker Micropogonias undulatus 

 (February- April; Barger 1985) in the northern Gulf of 

 Mexico. It is likely that annulus formation in sagittae 

 of these species is in response to environmental fac- 

 tors and is not related to reproductive seasonality, since 

 all three species exhibit different spawning seasons: red 

 drum, August-October (Wilson et al. 1989); black 

 drum, December- April (Beckman et al. 1990b); Atlan- 

 tic croaker, September-March (White and Chittenden 

 1987). 



Sheepshead are relatively long-lived, with a max- 

 imum life span of at least 20 years based on our esti- 

 mates. Greater ages are likely since the Louisiana 

 gamefish record is 9.6 kg (Louisiana Outdoor Writers 

 Assoc. 1987), and the maximum sized fish in this study 

 was 3.9 kg. The maximum age we observed for sheeps- 

 head is greater than reported for other Gulf/U.S. Atlan- 

 tic sparids (Table 1). However, great longevity is 

 apparently not unusual for this family, as greater max- 

 imum ages have been reported for sparids elsewhere 

 (Table 1). 



Length-weight regressions for males and females 

 were not significantly different (P = 0.991 for inter- 

 cepts, P = 0.647 for slopes). However, since the ex- 

 ponents are used in growth models, regressions are 

 presented for both sexes. Regressions were, 

 for males: 



Weight = 4.48 x 10 ~ 5 FL 2 - 88 r 2 = 0.943 

 for females: 



Weight = 5.30 x 10" 5 FL 2 - 86 r 2 = 0.926 



sexes combined: 

 Weight = 5.46 



x 10 " 5 FL 21 



0.923. 



The separation of sexes in growth models resulted 

 in a significantly better fit by length and weight when 

 compared with models in which sexes were combined 

 (P<0.001). Therefore, separate von Bertalanffy growth 

 curves for males and females were used to model 

 growth in length (Fig. 3) and weight (Fig. 4). Residuals 

 appeared normally distributed about the regression 

 lines. Growth models fit were, by length, 

 males: 



-0.417(t+0.90m 



419(l-e 



Lt 



females: 



L t = 447(1 

 and by weight, 

 males: 



W t = 1900(1 

 females: 



W, = 2557(1 



>) r 2 = 0.589 



6-0.367(1+1.025)) r 2 = 0.532, 



e -0.280(t + 2.657)\2.88 r 2 _ Q.549 



-0.219(t+3.061)\2.8E 



)2.85 r 2 = 0.474, 



The growth curves suggest rapid growth for sheeps- 

 head to an age of 6-8 years, after which an asymptote 

 is approached. The values of K, the von Bertalanffy 

 growth coefficient, for sheepshead are relatively high 

 when compared with other sparids (Table 1 ) and to non- 

 sparid perciform fish of similar size (see Pauly 1980). 

 This indicates that sheepshead exhibit relatively rapid 

 growth to an asymptotic size. This could be a result of 

 living in the highly productive waters adjacent to the 

 Mississippi Delta. 



