536 



Fishery Bulletin 88 13). 1990 



Figure 3 



Monthly length frequencies for red drum from the Atlantic coast of 

 Florida. No collections were made in June 1982. Horizontal bars show 

 length ranges for otolith-aged year-classes and are labeled for year- 

 class and age in years. 



Matagorda Bay (Wakefield and Colura 1983), during 

 winter in Aransas/Corpus Christi Bay (Pearson 1929), 

 and as early as January in all Texas bays (Matlock et al. 

 1987). Red drum deposit a first annulus on otoliths and 

 scales during their second winter, when they are about 

 14-18 months-old (Pearson 1929, Rohr 1964, Theiling 

 and Loyacano 1976, Hysmith et al. 1983, Wakefield and 

 Colura 1983, Matlock 1984, Matlock et al. 1987). Ap- 

 parently, juvenile red drum that measure 40-100 mm 

 during their first winter (Kilby 1955, Peters and 

 McMichael 1987) do not form an annulus; our smallest 

 specimen with an annulus was 379 mm. 



Red drum grew rapidly until age 4 or 5, and then 

 growth slowed markedly (Table 3; Fig. 5). For each 

 coast, the average observed sizes of fish ages 1-3 were 

 not significantly different between sexes (Student's t- 

 test; p>0.10 in all cases). However, in comparing 



Figure 4 



Mean monthly marginal increment ( ± 1 SD) for red drum in Florida 

 waters with (a) one and (b) two annuli on otolith sections. Differences 

 between coasts were not significant (ANOVA, p>0.05). therefore 

 pooled data are presented. 



coasts, the average observed sizes were significantly 

 larger (p<0.001) at ages 1 and 2 on the Atlantic coast 

 than they were on the Gulf coast. After age 2, growth 

 appeared to be slower on the Atlantic coast; however, 

 the variance for age 3 lengths was significantly greater 

 (F-test; p<0.05) on the Atlantic coast. Sample sizes of 

 older age groups were too small to test for statistical 

 differences. 



Lengths predicted from the von Bertalanffy growth 

 curve agreed with the average observed lengths of red 

 drum on the Gulf and Atlantic coasts (Table 3; Fig. 5). 

 Asymptotic length (L^) was significantly larger (Stu- 

 dent's i-test, p<0.01) on the Atlantic coast than on the 

 Gulf coast, while the Brody's growth constant (A') and 

 age at zero length (^,i) were not significantly different 

 (j:»>0.05). Therefore, predicted lengths were greater 

 at all ages for Atlantic coast red drum than for Gulf 

 coast fish. Our estimates of asymptotic length are 

 generally greater than other reported values: 717 mm 

 TL (680 mm FL), 835 mm TL (789 mm FL), and 803 

 mm TL (760 mm FL) for Lower Laguna Madre, Mata- 

 gorda, and Galveston Bays in Texas, respectively 

 (Wakefield and Colura 1983); 918 mm TL (865 mm FL) 

 in Texas bays (Doerzbacher et al. 1988); and 950 mm 

 TL (894 mm FL) in Mississippi Sound (Rohr 1980). This 

 suggests that red drum grow larger in Florida or, as 



