Etude de la qualité des eaux d'alimentation de l'écloserie de la Ferme Marine de Douhet (FMD), pour une amélioration de la survie larvaire de la daurade royale (Sparus aurata)

This study aimed to analyse the quality of the sea water flowing into the marine farm of Douhet, a gilthead bream hatchery, from the marsh-seawater reservoir to the entrance of the hatchery. The basin-seawater reservoir is not stratified in the pumping area. As a consequence, the measurements carried out at the surface to the right of the pumping dock give a good evaluation of the quality of the seawater pumped in depth. The high sensitivity of gilthead bream larvae to the water PH during the first two weeks of their larval life, and the values measured in the circuit seem to be an explanatory parameter to the observed mortalities. The water flowing into the hatchery retains, after pre-treatment, a nycthemeral PH variability, with maxima, at the end of the day, frequently reaching the limit level of 8.0- 8.2 recommended for a good survival of the larvae (Parra et Yufera, 2002). It is strongly recommended to conduct a daily water PH monitoring campaign, at the end of the day (16H-17H), in the larval rearing ponds, in order to know the maximum PH values of the water in direct contact with the larvae. If needed, a PH regulation system for the water of the buffer pond flowing into the larval ponds, should be implemented in order to maintain values inferior to 8.0 during the first two weeks of the larvae's life.