Société nationale de protection de la nature et d'acclimatation de France, Paris (FRA)
Abstract
Fish communities in the Camargue wetlands, both temporary
and permanent marshes as weil as irrigation and drainage canals,
were studied from 1977 to 1980. The main part of this work was
carried out in wetlands isolated from direct contact with the sea by a dike, the Digue à la mer. Three major types of wetlands and
their associated fish species are described in the Camargue : the
freshwater (0-5 g/1 Cl-), the brackish (5-16 g/1 Cl-), and the very
brackish (16-35 g/1 Cl-). A significant relationship (P < 0.01 )
was found between the species richness and the surface area.
The slope of this regression (0.134) is lower than that found for
other aquatic systems. Four associations of fish were determined
and their meaning is discussed . The biomass of temporary freshwater
marshes ranged between 13 to 76 kg/ha and was much
lower than those found in the small freshwater canals : 112 to
2 544 kg/ha. Common carp, Cyprinus carpio L., is the dominant
species in freshwater wetlands (70 to 85 % of total biomass).
A space partitioning between the immature and the adult carp is
described. ln one waterbody studied south of the Digue à la mer,
linked temporarily with the sea, the fish community composition
underwent frequent and rapid changes according to the variations
of environmental factors. The salinity appeared to be the most
important factor affecting diversity and eveness of the fish community
in this etang. A canonical analysis was used to determine
which of the environmental factors bad the greatest impact on
the abundance of the different fish genus. Only 46.2 % of the
fish species studied reproduce in the Camargue, while 35.9 %
migrate to the sea for spawning. The importance of a link with
the sea as weil as that of a sound water management plan for
the Camargue as a whole are pointed ou
