Most species of angler harvested fish are "sustainable". That is the job of fisheries managers, to make sure fish populations sustain themselves. That said, there are so many types of fish and fisheries that it is a hard question to answer. Freshwater/saltwater/river/lakes/streams/and ponds all are different. Perhaps the most "sustainable are panfish such as sunfish, perch, and crappie. All that is needed is a light weight rod and reel, some hooks and bobbers and some small worms. Panfish creel limits are usually generous, as panfish are capable of overpopulating. That's a short answer to a question that could fill a book.