Monitoring of Mussel Populations (Mytilus galloprovincialis) in the Berre Lagoon – Bouches-du-Rhône

Annual monitoring since 2006 at the 31 stations around the Berre and Vaïne lagoons, and from 2006 to 2009 at 4 control sites.

Within the context of rehabilitating the Berre and Vaïne lagoons, biological objectives were fixed by the state. These included the reintroduction of the Mediterranean Mussel (Mytilus galloprovincialis), its development and reproduction. The abundance of Mediterranean Mussel populations is monitored at the 31 stations evenly distributed around the Berre and Vaïne lagoons and at 4 control sites (3 transects per site from the shore to the lower edge of the population settlement).

The population of the introduced species of Musculista senhousia (south-east Asian), introduced in Berre in 2006, is also taken into account. This monitoring is implemented within the context of a research and development partnership contract. The abundance of both species is evaluated by estimating the average coverage of the population on the sea floor according to an abundance code ranging from 0 to 5. An average abundance index is calculated, based on observation frequency and the species/genus coverage code, and is used to monitor population changes. Photographs have been taken since 2006 on each transect at every 20m.

Since 2010, only the 31 stations around the Berre and Vaïne lagoons have been monitored. Readings are taken at the same time as those monitoring macrophytes. For information, from 2006 to 2009, the status of Mytilus galloprovincialis populations (size/weight ratio, reproduction stages and reproduction capacity, condition index) was also monitored on 4 control sites in partnership with Ifremer. This information is not included here, as it was only conducted over a 4-year experimental period.