NOTE Porch el a\ A growth model for Sciaenops occllatus 



151 



10 15 20 25 30 35 40 



35 J 

 30 - 

 25 



20 - 



15 -- 



10 - 



5 



B 



12 3 4 5 



Age 



Figure 1 



Fit of the proposed seasonal growth model to red 

 drum length at age data: (A) the fit for all ages; 

 iBi the fit for the younger ages. 



g 



o 



2 3 4 5 6 



Age 



Figure 2 



Growth rate coefficient from seasonal model as a 

 function of age. 



suggests that the parameters for all of the models were 

 estimated fairly precisely (Table 2). 



The new model, either with or without the seasonal 

 component, has both practical and theoretical advantages 

 over the four other models examined in this study. By vir- 

 tue of its greater flexibility, it was able to fit the red drum 



data significantly better than the linear and double von 

 Bertalanffy curves (its nearest competitors). Moreover, the 

 Richards and linear von Bertalanffy curves are theoret- 

 ically disadvantaged because their parameters have no 

 physical interpretation. The double von Bertalanffy curve, 

 although it has a physical interpretation, suffers because 

 it allows only a single discontinuous change in the growth 

 rate at one age rather than a continuous change through 

 time. For these reasons, the new model should be more 

 widely applicable than the others, particularly for species 

 that change habitat preferences with age or are subject to 

 strong seasonal environmental fluctuations. 



Acknowledgments 



We thank C. Legault, G. Scott, S. Turner, D. Vaughan, and 

 an anonymous reviewer for their helpful comments. 



Literature cited 



Akaike, H. 



1973. Information theory and an extension of the maximum 

 likelihood principle. In Second international symposium 



