It can be difficult to navigate choices in stores, but looking for certain verified certification labels and asking questions of restaurants/stores when you can is the best start. Most if not all the abalone sold in stores (locally) comes from farmed sources (partially because free diving is currently banned for a couple years). There's actually a really big abalone farm under the fisherman's wharf here in Monterey, and those farmers not only provide a good portion of the abalone steaks to local restaurants, they are also some of the only people with a permit to collect kelp from the bay!