Rationalisation de l'échantillonnage biologique pour l'évaluation des stocks des pêcheries marines en golfe de Gascogne

The aim of the project "rationalization of biological sampling for stock assessment of marine fisheries in the bay of Biscay" is to perform statistical methods and computer programs allowing to test prognoses and diagnoses based on estimates of fishing mortalities, recruitments, yields per recruit, and the "gain-loss" function. The project gathers the laboratories of the community working on the Bay of Biscay fisheries, namely - Santander in Spain (1. E. 0) - La Rochelle and Lorient in France (IFREMER). A descriptive study has been carried out. The prepared documents contain a description of the procedures used to collect the information, by each of the laboratories involved, on: - landings - biological samplings. More comprehensive data have been gathered on the species selected for simulation studies : - hake (Merlucius merluccius), - monkfish (Lophius piscatorius and L. budegassa), - megrim (Lepidorhombus whiffiagonis and L. boscii). In order to have available data, the laboratory of Santander has started a program to age monkfish (L. piscatorius) and megrim (L. whiffiagonis). So do the French laboratories for hake and megrim. Theoretical studies are related to the use of applied mathematical and statistical techniques in fishery research : - sampling techniques which allow to rationalize the sampling designs by considering both cost and accuracy, the so called "delta methods" associated with the use of Taylor's expansions which allow investigations on biases and variances and provide a tool for sensitivity analysis. Indeed, the consequences of inaccuracy related to the choice of the values given to some parameters can be easily assessed by sensitivity analysis which synthesizes vulnerability of a diagnosis to this uncertainty...