A Method for Finding the Limits of Application of the von Bertalanffy Growth Model and Statistical Estimates of the Parameters

The following expression is derived expressing the instantaneous growth rate (G) in terms of length (l) the power of the weight–length relationship (b), and the Bertalanffy growth parameters (K and L ∞ ): G = bK(L ∞ /l − 1). Since this is valid for a length (or age) range in which growth conforms to the Bertalanffy model, a plot of G vs. 1/l should be linear with the intercept on the G axis being −bK and on the 1/l axis being 1/L ∞ . Since the variables can be measured independently, deviations of points from the regression can be tested and the limits of validity of the model ascertained. In addition, confidence limits of K and L ∞ can be estimated. Two examples compare results with those using previous methods.