It depends on what you mean sa pamamagitan ng the question.
If you mean that ALL dolphins were to be captured somehow and kept in tanks - then no. Dolphins should have the right to swim freely in the wild.
If you mean SOME dolphins should be kept in a tank, then yes. Reason for this (at least mine), is for conservation purposes.
Let's suppose that you have a breed of yellow (that i made up) dolphins that you have in an aquarium. That breed is dying out, and at a fast pace. So, sa pamamagitan ng having those dolphins in that tank (assuming you are keeping it healthy, giving it a lot of puwang to swim and plenty of chances to interact with other dolphins), you not only preserve the EXISTANCE of those dolphins, but you also help bring those dolphins back to the wild.
If it's because it's injured or disabled somehow, then yes. If it's at a good place like Seaworld and will be released to the wild after a little while, then yes. If it's just for ipakita and will not ever sa pamamagitan ng released, then no.
