Fischer et al.: Demographic structure of Lut/anus campechanus in the northern Gulf of Mexico 



599 



Table 3 



Chi-square if), degrees of freedom (df ), and P-values for likelihood ratio tests for comparing FL and TW von Bertalanffy growth 

 models and parameters among sample locations (states). AL= Alabama; LA= Louisiana: and TX=Texas. n/a=not available. 



r 



df 



P 



r 



df 



p 



AL-LA 



FL model 



2.54 

 1,28 

 0.11 



TW model 



2.15 

 1,29 

 0.14 



FL model 



5.14 

 1,34 

 0.023 



TW model 



38.8 



1,27 



4.7x10" 



AL-TX 



LA-TX 



k 



FL model 



13.67 



1,34 



0.0002 



21.53 



1,34 



3.48xl0" 6 



5.8 

 1,32 

 0.015 



k 



TW model 



21.3 



1,27 

 3.9x10" 



37.8 



1,27 



7.97xl0- 10 



16.77 



1.26 



4.2xl0" 5 



10.16 

 1,32 

 0.001 



15.1 

 1,26 

 0.001 



k 



9.8 

 1,32 

 0.002 



n/a 

 n/a 

 n/a 



reached and growth in length becomes negligi- 

 ble. This pattern of rapid growth was similar to 

 that reported in previous studies (Szedlmayer 

 and Shipp, 1994; Manooch and Potts, 1997; 

 Patterson, 1999; Wilson and Nieland, 2001). 

 However, our models predicted smaller L r and 

 higher values of It. Because of the minimum 

 size limits on the recreational fishery, very few 

 fish under age 2 years (>300 mm FL) were in- 

 cluded in our sample populations. We forced our 

 models through t = to more accurately pre- 

 dict juvenile growth, which in turn increased 

 our estimates of k. In addition, we had a much 

 larger sample population that included more 

 older, larger fish than most of the previously 

 cited studies. These larger fish pulled the curve 

 down, driving the lesser estimations of L M . The 

 lack of significant differences in growth param- 

 eters between the Alabama and Louisiana mod- 

 els supports the findings of previous research, 

 which indicates that Alabama and Louisiana 

 red snapper grow at similar rates and reach 

 comparable sizes (Patterson et al., 2001). How- 

 ever, values of L M for Texas red snapper were 

 significantly smaller than parameters predicted 

 for Alabama and Louisiana red snapper. In- 

 terestingly, Texas had a value of k that was 

 significantly larger then that for Alabama and 

 Louisiana and this would indicate that Texas 

 fish obtain a smaller maximum theoretical FL 

 but reach it at a faster rate then fish from Ala- 

 bama and Louisiana. 



Von Bertalanffy growth models of mean 

 weight at age produced similar results, in- 

 dicating that Texas red snapper obtain sig- 

 nificantly smaller maximum theoretical TW 

 than fish from Alabama and Louisiana. Fish 

 sampled from tournaments were excluded from 

 all growth models to more accurately reflect 



30 35 40 45 



B 



15  



12 - 



5 10 15 20 25 30 35 40 45 

 Age (yr) 



Figure 5 



Observed (A) mean fork length (mml at age and (B) mean total 

 weight (kg) at age for red snapper iLutjanus campechanus) from 

 Alabama, Louisiana, and Texas. Plotted lines are weighted von 

 Bertalanffy growth functions fitted to the data. 



