Rooker et al.: Variability in growth, mortality, and recruitment of Sciaenops ocellatus 



587 



200 



100 



^ 



1994 



2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 



"5 1000 

 < 



2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 

 Standard length (mm) 



Figure 4 



Length-frequency distributions of postsettlement red drum col- 

 lected from the Aransas Estuary in 1994 (« = 1306) and 1995 

 (n=8144l. 



derived for red drum, we predicted that the length of 

 a 40-d individual ranged from 20.2 mm ( 1994) to 18.2 

 mm ( 1995), which was similar to the predicted length 

 of a 40-d individual collected in Tampa Bay (20.5 

 mm). Although seasonal trends in growth variation 

 were not examined in this study, Rooker and Holt 

 (1997) observed considerable variability among co- 

 horts of newly settled red drum (0.5-0.8 mm/d), and 

 growth was generally highest for midseason cohorts. 

 Mortality rates of red drum were substantial and 

 varied over spatial and temporal scales. Interannual 

 estimates of mortality were similar and losses ranged 

 from 12.5 to 13.0%/d (Z=0.13-0.14). Consequently, 

 cumulative mortality during the settlement and early 

 postsettlement period (12-d period) was relatively 

 high; only about 20'7f of the initial settlers survived 

 to 40 d. Although no estimates of mortality exist for 

 red drum larvae and early juveniles, these mortality 

 rates are comparable to values reported for other 

 marine fishes during the early life stage. Houde 

 (1987) reported instantaneous daily mortality coef- 

 ficients for five species of marine fishes during the 

 larval stage (first feeding to late-stage larvae) and 



predicted values ranging from 0.04 to 0.18 (4-16%/d). 

 In addition, Houde and Zastrow ( 1993) summarized 

 natural mortality data for teleost larvae from a vari- 

 ety of sources and reported that the mean instanta- 

 neous daily mortality rate of larvae in estuarine habi- 

 tats was 0.266 (23%/d). Also, McGurk (1986) devel- 

 oped a general mortality equation for marine fish 

 lai-vae (based on dry weight), and using his equation 

 we predicted the mortality rate of individual red 

 drum 8-10 mm (ca. 750-1500 |ig dry wt) would be 

 approximately 0.05-0.11 (4.9-10.4%/d). 



Although interannual patterns of mortality were 

 insignificant, variability within a year was relatively 

 high and a seasonal trend was evident. Cohort-spe- 

 cific estimates indicated that mortality rates were 

 lowest for red drum produced in the middle of the 

 spawning season ( 107c/d), when densities within the 

 seagrass meadows reached maximum levels. Con- 

 versely, mortality rates for early and late-season co- 



