Estimation du stock de moules sur bouchots en baie du Mont Saint-Michel

The quantity of mussels cultivated on wooden poles called « bouchots », in Mont Saint-Michel bay, has been estimated in april 2002, by volume, number and weight. To do so, a sampling strategy has been conceived, operated and then optimized, taking into account the spatial distribution of this stock and the material and human constraints (especially the amount of persons and working days available). The sampling plan uses procedures of stratification, degrees, regression, so as to reach the optimum precision related to cost. The operation took a great advantage of the efficient help of mussel farmers. During the first day, the task consisted to estimate the number and position of poles occupied by mussels, with the help of 5 persons on boat. The following 2 days, 14 persons walked through the entire area, to estimate mussels volumes in situ and sample one liter on selected poles, for number and weight subsequent estimations. As a whole, around 3.4 billions of mussels, with a mean weight of 3.2 grams, were estimated at that time, weighing more than 11 000 tons. The relation between this instant stock and the next commercial production remains to be precised.