Pacific oysters (Crassostrea gigas) from two genetically differentiated populations from the Wadden Sea - one from Texel, the other from Sylt - were reciprocally translocated between the sites at the beginning of June 2012. Half of the oysters were additionally pretreated with antibiotics to remove resident microbiota. Local controls were included as well, resulting in four groups at each site: antibiotic treated local or translocated, and control local or translocated oysters.Hemolymph samples were taken immediately after the pretreatment in the lab and then on 3 (monthly, Texel) and 5 (biweekly, Sylt) occasions in the field. Exact position of each oyster in the field was recorded, so that the data allow for study of spatial patterns of oyster hemolymph microbiota. One seawater sample is included for reference for each sampling point.