| SPARRE (1985) has generalized the technique initiated by SCHNUTE et FOURNIER (1980), FOURNIER et BREEN (1983) in order to deal with several length frequency distributions, instead of a single histogram. This paper develops the same approach. Beyond some considerations about the possible constraints, the new points correspond on one hand to analytical derivation of the first and second derivatives of the objective function, on the other hand to the analysis of colinearities. It is suggested for the second question to perform a principal component analysis of the invert of the Hessian matrix of the objective fonction. An example, borrowed from SPARRE (1985) is treated, which suggests that colinearity problems could be extremely important, reducing severely... |
