Les chalutages experimentaux: Utilisation de la temperature et de la profondeur comme variables auxiliaires.

Very often stratification of bottom-trawl surveys is done by using a stratified random sampling scheme. If a survey is directed towards a group of species, the sampling scheme has to be a compromise between these different interests. So the sampling scheme is not totally efficient for each of the species. The use of auxiliary variables, as depth or temperature, looks as if such supplementary informations could neither improve the efficiency of the estimators nor the subsequent analysis (analysis of covariance).