on the following subject:
"Sustainable management of a fishery resource using a model: the example of Ruditapes philippinarum (Adams and Reeve, 1850) in the Etang de Berre".
Thesis supervisor: Jean-Christophe Poggiale , professor AMU
SUMMARY | The aim of this thesis is the sustainable management of a fishery resource, using the example of the Manila clam Ruditapes philippinarum (Adams et Reeve, 1850) in the Etang de Berre (near Marseille - France). In order to better adapt a fisheries management model in the Etang de Berre, it is necessary to improve knowledge of this species in this environment on the basis of in situ experiments. The size is 20 - 23 mm. Clams reproduce between March-April and September-October when water temperatures are above 11°C. The VBGF parameters are and . In the Etang de Berre, predation is considered negligible. Natural mortality is therefore linked to senescence and disease, which have a fairly low prevalence, varying between 0.64 and 2.85 depending on the size of the individuals. In 2019, a survey of the entire Etang de Berre between 0 and 5 m showed that the abundance was 552.07 million individuals for a biomass of 2,903.62 tonnes, with a wide disparity in distribution: two areas accounted for 69 % of the total abundance and 80 % of the total biomass. These areas have been monitored regularly and show a decrease in abundance of 10 %, probably due to poaching. On-foot fishing was monitored using counts and was estimated at 62 tonnes of clams for the summer of 2018. On an annual scale, professional fishing pressure is 142 tonnes. All these in situ data are integrated into a management model combining an individual DEB model feeding a population model in three size categories (juvenile, adult between 20 and 30 mm and adult with the mesh). The model's outputs are used to compare fishing scenarios at COPIL meetings and to assist decision-making. The methodology used in this thesis can be transposed to other species/environment pairs. The originality of this thesis lies in the fact that it was carried out in parallel. Each study fed off the others and vice versa.
KEYWORDS : Ruditapes philippinarum, Etang de Berre, life cycle, model, fisheries management.