Use of the original von Bertalanffy growth model to describe the growth ofbarramundi, Lates calcarifer (Bloch)

In the original von Bertalanffy growth equation, the rate of change in body mass of an individual is assumed to result from two opposing biological pr ocesses: anabolism and catabolism. Because this differential equation canno t be solved analytically, some of its analytically solvable special cases a re commonly used, despite their restrictive assumptions. In this study, I u sed a generalization of the original von Bertalanffy growth equation and so me of its commonly used special cases to estimate parameters from a set of tagging data on times at liberty, lengths at release, and lengths at recapt ure of a centropomid perch (Lates calcarifer) and provide a method for dete rmining the anabolic and catabolic rates of animals in their natural enviro nment. Fitting the original von Bertalanffy growth equation to the tagging data suggests that a 1% increase in body mass of the fish corresponds to a 0.8721% increase in anabolic rate and a 1.0357% increase in catabolic rate. Alternatively, L. calcarifer may be interpreted as exhibiting a strong sea sonality in growth: it grows fastest in length at the start of autumn, grow s less until a full stop in the middle of winter, shrinks until the middle of spring, and then resumes a positive growth for another cycle. Consequent ly, it is unnecessary to use the analytically solvable special cases of the original von Bertalanffy growth equation in data analysis, unless their as sumptions are validated. I also explain why Pauly's index of growth perform ance is adequate and propose an index of catabolic performance.