It was only a few decades ago that scientists and medical scientists insisted that animals didn't have emotions like we did, let alone some kind of sentience. I remembered being really angry with one of my best friends who was in med school, participating in animal experiments, when she insisted to me that "animals don't feel pain like we do". I tried arguing the point, and she pulled out what she was taught in class, and how "reading animal traits like human traits is just anthropomorphizing them. There's no logical reason to think that they are conscious of pain".
Dolphin trainers have been working up a sign language to direct their performing animals for a while. I didn't know it, but they already have a sign (the one they co-opted makes me giggle) to tell/ask a dolphin to make up a new trick by itself. Now the trainers have figured out that dolphins are smart enough to put the sign "together" with "create new trick". When asked to do so, two dolphins conferred below water, and then performed a syncronised trick on the water surface that they hadn't performed together before.
Well, I hope these captured beings are finding some captivity activities and interactions that compensate a little for being stuck in tiny enclosures compared to the vast open ocean.