hello, Make sure they are in season. In North America (where I think you’re located) oysters are considered in season during months that have an “r” in them (so they’re out of season May through the end of August) — two reasons — first, summer is the spawning season, and the oysters are generally leaner and don’t taste very good, and second, the warmer waters of summer are perfect to encourage any bacterial growth in the water and therefore in the oysters themselves.thanks