Oyster and mussel aquaculture doesn't typically have the pellet feed, antibiotics, poor crowded conditions, poor water quality associated with fish farming practices, especially from international suppliers. Though they can get shut down in terms of harvest/sales, if there is a large influx of freshwater due to flooding. That water may bring in more pesticides, fecal coliform, sewage, etc. into the bays where the farms are located.
I like rope cultured mussels. They don't have sand 😉.