Starfleet employs dolphins in their starship navigation systems, which sounds very much like property. This seems contradictory if they are considered sentient
In The Perfect Mate Geordi takes the Ferengi merchant Par Lenor to see the dolphins in their catacean ops center. This is where the bottleneose dolphins (tursiops truncatus) work as "navigation specialists."
LAFORGE: Listen, have you had a chance to see the dolphins yet? This is something you really just don't want to miss!
The way Geordi talks about them doesn't seem respectful. Would he also say, "Have you had a chance to see the vulcans yet?" It seems more appropriate to say "have you met the dolphins yet" if they were respected sentient beings.
Yet in this same episode Riker is openly upset at the idea that the Krios were transporting a sentient being, Kamala, as property to be exchanged in peace talks between Valt and Krios:
KAMALA: It is not complicated at all, Briam, and the Captain has no tolerance for prevarication. I'm a gift, to Alrik of Valt.
RIKER: You mean you're using this ship to transport a sentient being as property?
BRIAM: Not as property, as a gift, and I was concerned that you might not entirely understand.
PICARD: Your concern was justified, Ambassador.
KAMALA: You're angry. Why?
PICARD: There is a provision in the Federation Constitution that protects an individual's fundamental rights.
Are dolphins sentient in Star Trek?