OYSTER FARMING AND EXTERNALITIES: A BIOECONOMIC APPROACH

摘要

The management of the French shellfish industry has been based for a century and a half on a Territorial Use Right in Fisheries (TURF) scheme. This was meant to ensure control over access and use and was seen as a potential remedy for overexploitation. But the resource, i.e. shellfish nutrients, is mobile and carried by streams. As a consequence, space allocation is far from being an efficient tool to share the resource between producers. The history of the French shellfish industry is marked by a series of overfishing crises occurring in most of the open-access shellfish beds located all along the French coastline. When the concession system was enforced (1852), it was designed to cope with congestion and overfishing issues more than with the development of shellfish culture. After turning into a breeding activity in the late nineteenth century, the oyster industry kept suffering major crises such as massive diseases. Their occurrence can be analysed in terms of overexploitation resulting from technological externalities. This article presents the current progress in the bioeconomic modelling of the oyster-growing industry in the Bay of Bourgneuf (Pays de la Loire). In this bay, 400 firms, mostly family-sized, are being conceded 1,000 ha and sellabout 1,0000 tons of Crassostrea gigas oysters a year. The model will highlight the externalities that result from the concession system and provide a basis for discussing policy measures.