Zusammenfassung: The statistical model for the Petersen method is a hypergeometric distribution. Approximation to a binomial distribution has been used, and the usual method for this binomial model is based on approximation to a normal distribution. The Bayesian statistical model for a binomial distribution, which assumes that the prior distribution of parameters is uniform, corresponds well with the conventional method. However, the Bayesian statistical method for a hypergeometric distribution which assumes the uniform prior distribution is not feasible. The prior distribution according to the inverse squared parameter is natural for this model. Beta function and zeta function are important to understand these methods. This model is simpler to understand and easier to calculate by micro-computer than the conventional method.

Zusammenfassung: With respect to the sexual dimorphism in growth of fish, computer simulation of individual growth variation was made in terms of coefficient of variation (CV) and skewness (sk) of frequency distribution. Normal distributions of initial body length, specific growth rate in exponential growth coefficient in asymptotic growth and asymptotic value (each consisting of 500 monosexual distributions) were supposed. In exponential growth both CV and sk of the bisexual distributions increased more quickly than the two monosexual distributions. In asymptotic growth (Bertalanffy and Logistic) CV of the bisexual distribution was always greater than the monosexual distributions, and sk of the former was greater in positive value and smaller in negative value than those of the latter all the time.