People are currently talking mostly about orca captivity because of Blackfish, because that was what the film was specifically about. On top of this, part of the reason that captivity is so detrimental to whales and dolphins is their intelligence.

I'm sure some people don't think about other marine life in captivity, but that doesn't mean they wouldn't care if someone were to show them the detrimental effects captivity has on certain animals. Just like I know people who didn't give Sea World another thought until they saw the documentary and decided to do more research and realized that something they were brought up to think was normal/fun was pretty disturbing.

On the blogs I follow re: animal welfare and marine life, people talk about (including but not limited to): sharks, seals, penguins, dolphins, whales, walruses, 'regular' fish, mantas, etc, including the downsides of captivity for many of these species.