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Fish communities in the Camargue

Fish communities in the Camargue

Objectives

The hydraulic system of the Camargue Delta has functioned in a completely artificial way for decades: freshwater inputs are mainly controlled by pumping from the Rhone for irrigation, and marine inputs by opening the floodgates at the Pertuis de la Fourcade. This project seeks to characterise and explain the temporal and spatial structure and dynamics of fish communities throughout the Camargue, and those of decapod crustaceans, in function of environmental conditions, hydraulic management of the system, and the introduction of new species, such as the Wels Catfish, and the Topmouth Gudgeon.

Measuring a juvenile Dover Sole (Solea solea) Measuring a juvenile Dover Sole (Solea solea)

Actions and methodology

The project was initiated in 1976, involving a large number of studies aimed at better understanding the functioning and dynamics of freshwater and brackish-water fish populations, and studying the life history traits of numerous species.

Three monthly long-term monitoring programmes were set up by Alain Crivelli back in 1993:

These sampling campaigns are conducted using a fixed-station method with passive fishing gear (hoop nets, capéchade trap nets) and characterise the populations in terms of species diversity, abundance, biomass, and size range.

Monthly sampling of the fish population in the Fumemorte canal has been performed continuously since 1993. During the first year of monitoring, the Wels Catfish (Silurus glanis), an opportunistic super-predator, entered the canal after the accidental opening of a sluice gate in the fish farm that was adjacent to it. Monthly monitoring showed a sharp reduction in other aquatic species after that time, especially as of the 2000s. In order to offset this decrease, a Catfish regulation plan (using hoop nets and gillnets) has been tested from 2009 to 2018 on a 2.5-km stretch of the canal. Studies are being carried out to better comprehend the biology and feeding ecology of the species, and its impact on this confined ecosystem.

Threespined Stickleback (Gasterosteus aculeatus) © F.Le Borne / Tour du Valat

From 2009, monitoring on the Étang des Impériaux and on the Étang du Vaccarès have only targeted the European Eel [1]. The monitoring on the Impériaux lagoon was stopped in 2014. Since 2019, the specific diversity of the fish populations is continuously characterised and the complete treatment of catches is carried out every 3 years in the Étang du Vaccarès in partnership with the Société Nationale de Protection de la Nature / Camargue National Nature Reserve.

In the past, shorter-term studies were also conducted on fish populations in the lower lagoons, particularly the Etang du Tampan, and the biological connectivity between the sea and the Vaccarès lagoon hydrosystem at the Pertuis de la Fourcade. From 2016 to 2021, hydrobiological connectivity was studied in the Camargue Saltworks Lagoons and Marshes [2] within the framework of a restoration project.

Results

Analysis of the data gathered in the Etang du Vaccarès and Etang des Impériaux showed the high resilience of the system, from an ichthyological point of view, regarding variations in salinity and water management (Poizat et al. 2004).

The fish monitorings in the lagoons and marshes of the former Camargue saltworks sites [3] were the subject of a study report (for more information [4]).

Team

Partners

Technical partners

 Financial partners

Publications