On the question of adequacy of estimation of the natural mortality of fishes by means of von Bertalanffy growth equation

The initial prerequisites for the application of the parameters of the Bertalanffy growth equation for estimating the maximum age of fish life (tλ) and the natural mortality rate (M) are analyzed. This approach has been proposed by D. Pauli and was widely used. Pauli found a regression dependence of the natural mortality rate on the parameters of the Bertalanffy growth equation (L∝, K) and environmental temperature (T) for various populations on a large amount of factual material. However, the presence of a causal relationship between the growth rate and the natural mortality of fish has not been proven, therefore, it seems doubtful whether it is possible to solve the inverse task – determining mortality rate by growth parameters. A numerical example shows that in reality the values of the parameters of the growth equation can vary over a very wide range depending on the original data and do not correspond to their biological interpretation. Therefore, the growth cannot be used to estimate mortality. Since mortality is the rate at which fish decrease in number, this rate should be used for estimation of mortality.