4.2 Generalities on coastal lagoons of France

The surfaces of the French lagoons vary from 15 000 ha (Berre lagoon) to 86 ha (Perols lagoon) and except in some cases (Berre, Thau) their average and maximum depths are generally very low (most of them less than 1 meter, Table I). Their water salinity is very different from one lagoon to another. It varies according to the seasons and depends mainly on the rain regime.

The water temperature and the dissolved oxygen ratio are also very variable: due to the low depth of these lagoons, they follow the trends of the air temperature; in winter the surface water layer can freeze, while in summer it can reach up to 30°C. The oxygen concentration is very often near to the maximum except in summertime; during this season annual dystrophic crises caused by the biodegradation of opportunistic macroalgae resulting from anoxic conditions can be observed regularly. The main temperature variations are caused by the wind regime which can generate daily variations of 10° C.

Table I: Characteristics of French lagoons

Legal framework and constraints

Fisheries and aquaculture activities in the French lagoons, as well as recreational activities, are submitted to the French national legislation.