Zusammenfassung: The paper describes methods of estimating population size based on survey removal data. The Zippin maximum likelihood model is presented with the possibility with microcomputer. The Carle and Strub method is considered most convenient and a microcomputer program is published.

Zusammenfassung: Habitat suitability curves and habitat use multivariate models of the barbel (Barbus barbus L.) are elaborated with data from 3 French rivers. The quality of the prediction and the sensitivity of the response show that the multivariate models are preferable.

Zusammenfassung: In mathematics, the age-length key method is an estimating method for the ratio of each distribution in a mixture of distributions. Although the maximum likelihood method is the principle of this estimation, this model is a nonlinear model with a restrictive condition. At first, Hasselblad solved this model by using a new iteration method with a computer. Although his method was regarded as the steepest descent method or EM algorithm, it is proved to be an application of Lagrange's indeterminate multiplier method to the iteration method. Nowadays, there are other useful algorithms of optimization, especially Marquardt's method, for this estimation.

Zusammenfassung: Leslie's removal method, which is used to estimate the initial population size and the removal ratio simultaneously, is modeled in terms of the product of binomial distributions. The approximation of these binomial distributions to the standard normal distribution presents a new method which has no bias for estimators. This is an improvement over the maximum likelihood method and the likelihood ratio test, and is essentially equivalent to a standard goodness-of-fit test. The confidence region on the 2-dimensional plane defined by the initial population size and the removal ratio gives each confidence interval. This region is defined by the chi-square distribution with 2 degrees of freedom.