I don't think it's a simple decision - that a particular animal should or shouldn't be kept in captivity. I remember being terrified of orcas as a child because of a misguided episode of Sea Hunt. Today's children are going to get a whole different perspective because of "Shamu" and will hopefully have an appreciation of these spectacular animals, and maybe work towards protecting them and other whales as they grow up. I saw the whale sharks at the Georgia Aquarium and it was great to see them. I'm disappointed that they haven't all survived. In some ways, most people consider it a good idea to kill sharks, as evidenced by almost 100 MILLION being killed EVERY YEAR. If a few amazing sharks in an aquarium can change some minds, maybe opinions can be changed before we have a world without any sharks at all.
Most of the whale sharks that came from Taiwan were taken from a fishing quota. Some were allowed to be captured every year for local consumption. It's certainly better for them to end up in an aquarium than be eaten. But now Taiwan has banned capture of whale sharks for consumption. Therefore more difficult to justify capture for aquariums now. It was easier when the choice was between it being eaten and it being in an aquarium.
The new Marine Life Park oceanarium in Singapore (opening in 2011/2012) has dropped plans to display whale sharks after protest from NGOs and local public.
Good question. I would two studies, published within 6 months of each other, that say the exact opposite thing. Whale shark population thrives(Science Alert) Is the World's Largest Shark Shrinking? : Discovery News
2 facilities actually did try to keep Narwhal (Monodon monoceros), those places were the New York Aquarium in 1969, and the Vancouver Aquarium also kept them, but I do not know exactly when Here is my source: Cetacean Lifestyle
It's strange that belugas take to captivity relatively easy yet narwhals don't... I imagine that cetacean husbandry in the late 60's / 70's was not terribly good (if you think the orca pools at Sea World are small check out the size in the 1960's!). I imagine a solution to the tusk problem is to have pools that slope up like a beach - though the viewing glass would be an issue. I would bet you could keep them today with enough money and resources put in, though "should" you keep them is another issue...
It may be thought that sometimes, marine life refuges in the Arctic Zone (Canada, Alaska, Northern Europe...) should keep Narwhals for a moment, in order to rescue them before releasing in the wild. (as it's the case for many dolphins, porpoises, seals...)
