Favoring exchanges between the sea and the lagoons : a necessary support for the restoration of the functional role as fish nursery in the saltmarshes of Hyeres (Provence, France)

2020

Article référencé dans le Web of Science WOS:000675537200023

Le Diréach L., Astruch P., Changeux Thomas, Moussy F., Jehl C., Brodu N., Boursault M., Charpentier M., Gimond F., Harmelin-Vivien M., Lasceve M., Lucchini N., Lyonnet A., Roux M., Schohn T.

Vie et Milieu = Life and Environment, 2020, 70 (3-4), p. 243-252 ISSN 0240-8759

GECOMARS: International Workshop on Ecosystem Based Management, Marseille (FRA), 2020/02/04-05

The salt exploitation of the saltmarshes of Hyeres (Salin des Pesquiers and Vieux Salins sites) has led to the isolation of the lagoon from the sea to control evaporation. The question of whether or not the saltmarshes' ecological functioning is impaired with regard to the fish population is one aspect that has been studied at the ecosystem scale. During 2018-2019, 4 samplings with 4 mm-mesh size fyke nets (24 h fishing duration) confirmed that the two saltmarshes still have a relictual nursery role. If juvenile fishes were numerically dominant in the catches, adults were also present. A few euryhaline and permanent small-sized taxa (Atherinidae, Gobiidae, Syngnathidae) contributed to 90 % of the total abundance in the catches. The amphihaline migrator Anguilla anguilla (mainly adult stages) was the main contributor to the biomass of catches. Juveniles of commercial species such as Dicentrarchus labrax, Sparus aurata, Mugilidae and Soleidae were caught in autumn and spring when going back and forth between the lagoon and the sea. Their tolerance of a wide range of salinity enables them to benefit temporarily from good environmental conditions for their growth. However, considering the low connectivity and the high salinity of most of the ponds, most of those marine fish juveniles are probably trapped inside the lagoon. In both lagoons, the closer the sampling sites were to the open sea, the higher were the species richness and density of the juveniles, suggesting that other parts of the lagoons function as an ecological sink. The diversity of the fish assemblages of the saltmarshes of Hyeres is directly dependent on the effectiveness of the connection with the open sea. Among the different actions emerging from this study, the introduction of a sluice gate between the northern pond (Salin des Pesquiers) and the input channel could significantly enhance exchanges and potentially provide support for fish resources at sea.

Ecologie, systèmes aquatiques [036] ; Ressources halieutiques [040]

FRANCE ; MEDITERRANEE

Fonds IRD [F B010082561]

fdi:010082561