Asymptotic equations in growth studies — an analysis based on Anodonta piscinalis (Mollusca, Unionidae)

Abstract

The suitability of four asymptotic growth equations for describing growth of length in populations of Anodonta piscinalis was studied. The Kruger function showed the best fit with the observed values, but the other three equations (von Bertanlanffy, Gompertz, logistic) were not much worse. The Kruger function was also the best when lengths of very old and young individuals were extra polated from truncated data. Although the equations closely simulated the sets of material, we could find little evidence that their parameters (growth constant, asymptotic length) were suitable for comparisons between populations. Different cohorts and sexes within a population produced very variable numerical values for these parameters. The correlation between the mean length of the third annulus in a population and the growth constant produced by different equations for the same set of data ranged from 0.539 to —-0.640. The von Bertanlanffy equation was the least unsuitable for producing parameters for comparisons between populations.