An improved and rapid biochemical identification of the culturable aerobic bacteria species associated with Galician oyster production was performed by the combination of numerical taxonomy and sequencing of 16S rRNA gene. The 16S rRNA sequences of 23 representative bacterial isolates from different growing stages of Ostrea edulis, surrounding water, and phytoplankton were compared with related sequences from the EMBL database. These results were used to identify the phenetic clusters obtained by numerical taxonomy using the S_J/UPGMA with a similarity level of 74%. The combination of the two techniques was a useful tool for identifying 40 out of 75 representative aerobic Gram negative isolates comprising the bacterial community studied and for improving the phenotypical description of each identified species. It was mostly facultative psycrophilic α-Proteobacteria showing a great diversity. No specifity of bacteria, according to the geographical area studied was found. Almost all of the identified species were associated, for the first time, with different growing stages of oyster. Some could have a probiotic effect (Roseobacter gallaeciensis, Shewanella schlegeliana) or could be a potential risk for oyster cultures (Pseudoalteromonas piscicida, Pseudomonas anguilliseptica) or for humans by consumption (Acinetobacter johnsonii, Pseudoalteromonas tetraodonis).