Effects of food ration, water flow rate and bacteriological levels of broodstock on the reproductive conditioning of the European flat oyster (Ostrea edulis,Linnaeus 1758)

•Oysters conditioned with a food ration of 3 % produced the largest number of larvae.•Oysters conditioned at flow rate of 3 L h−1oyster−1had the highest mortality rate.•Highest levels of vibrio and heterotropic bacteria were found at 3 L h−1oyster−1.•Best larval production obtained at 3% food ration and 2 L h−1oyster−1flow rate.•Influence of bacteriological charge of broodstock is studied for the first time.