NOTE Matlock: Growth of five fishes tagged in Texas bays in the 1960s 



409 



bays was about 840-950 mm TL, whereas the sheeps- 

 head estimate was about 470 mm (Table 2). Daily 

 growth coefficients (K) were about 0.0005 (0.183 

 annualized) for black drum, southern flounder, and 

 spotted seatrout, and about 0.001 (0.365 annualized) 

 for red drum and sheepshead (Table 1). The 1960s 

 estimates of L^ for black drum, red drum, sheepshead, 

 and spotted seatrout in Texas were generally higher 

 than comparable estimates made in the 1980s. Red 

 drum L^ in the 1960s ranged from 879 mm in the up- 

 per Laguna Madre to 1177 mm in the Aransas Bay 

 system; L^^ was 918mm in the 1980s (Doerzbacher et 

 al. 1988). Values for black drum, sheepshead, and 

 spotted seatrout were as follows (1960s vs. 1980s): 844 

 mm vs. 798mm (Doerzbacher et al. 1988); fork length 

 (FL) 478 mm vs. 419 mm (males) and 447 mm (females) 

 (Beckman et al. 1991); and 836mm vs. 691mm (Green 

 et al. 1990), respectively. No estimates were available 

 for southern flounder in the 1980s. 



Red drum growth varied among bays. Estimates of 

 L^ for red drum in each bay system approximated 

 930 mm, except in Aransas Bay where L^ was 1177 

 mm, and K (annualized) varied between 0.3 and 0.5. 

 Reasons for the interbay variation in L^ and K for red 



drum in the 1960s are unknown. However, factors 

 affecting growth (e.g., fishing mortality, food supply, 

 red drum density, and environmental conditions like 

 salinity and temperature) varied among bays (Matlock 

 1984). 



The estimated values of L^^ for black drum and red 

 drum from fish tagged in the 1960s and 1980s appear 

 to be underestimates because the data include few adult 

 fish which reside mostly in the Gulf of Mexico (Matlock 

 1987, 1991). The addition of older adults would prob- 

 ably increase L^ and reduce K for both species, but 

 the change in parameter estimates would depend on 

 the average maximum age and size actually reached 

 relative to the largest fish included in the analysis. 

 Parameter estimates (standard error) for the von Ber- 

 talanffy model for black drum (0-58 years old) growth 

 in Florida were 1172mm (±9mm) and 0.124mm 

 ( ± 0.0003 mm), respectively. When the von Bertalanffy 

 growth equation was fit to length and age (from 

 otoliths) data for adults off Louisiana, the estimate for 

 L^ was lOOOmmFL (Beckman et al. 1991); recall, 

 L^ for Texas black drum was 844mmTL. However, 

 Beckman et al. (1991) questioned the biological signif- 

 icance of their L^ estimates because an asymptotic 



