1) They're unlikely to be sentient (few neurons, immobile)
2) If they are sentient, the farming practices look likely to be pretty humane
3) They're extremely nutritionally dense
Buying canned smoked oysters/mussels and eating them plain or on crackers is super easy and cheap.
It's an acquired taste for some, but I love them.
This was also the book that persuaded (and alerted) me to ostrovgegansim