Sylvie Lapègue

Ecological and Socio-Economic Implications of Environmental Change on French Shellfisheries

During the last century, shellfish farming in France has been based on three species. During the last 15 years, the number of episodes of mortality on different wild and cultivated shellfish species has increased, although the reasons behind these episodes of mortality are not yet well understood. The Pacific oyster (Crassostrea gigas), is considered an invasive species in France, and was introduced about 50 years ago in two bays and is now reproducing along the French coasts. At present, it is difficult to disentangle the increase in sea temperature and the invasive capacities of this species in their range expansion. To address this, a qualitative and quantitative study of phytoplanktonic distribution, which oysters feed on, was undertaken. Changes in the microbial community were observed to coincide with episodes of mortality. Other parameters such as salinity or acidity are also thought to be associated with higher mortality and subsequently, the impact of ocean acidification also needs to be considered. Socio-economic impacts of invasive species and shellfish mortality on French shellfisheries raises a number of questions and challenges that need to be more deeply addressed through an interdisciplinary approach.

Keywords: Oysters, Production, Diseases, Recruitment, Adaptation, Invasion

Figure: Shellfisheries activities in Marennes-Oléron Bay (© Ifremer / J. Prou).