Les méthodes delta en halieutique. Evaluation des sensibilites, approximation des biais et variances à l'aide de developpements limites

This report presents an introduction to so called "delta methods", associated to the use of Taylor's expansions, as a tool for sensitivity analyses. It starts with a mathematical and statistical summary about Taylor's expansion and moments of random variâtes. Special attention is paid to multivariate problems. The application of order 1 and 2 expansions to estimate variances and biases is exposed in great details. This report dedicated to fisheries scientists, is finally illustraded by an example associated to yield per recruit calculations, based upon JONE'S length cohort analysis.