There was a great deal of information (easy-to-read) on the site Max provided. One of the pages on killer whales (sorry, Max--that's what they called 'em!) described a bent dorsal fin problem of whales in captivity. I'm going to paste a little of that information here because it illustrates still another problem with wild animals in captivity:

Although bent or weakened dorsal fins are seen in the wild,
they are more common in aquarium facilities. It is particularly
noticeable in male orcas, who have narrower bases for
support than females. Scientists believe that gravity and
swimming patterns ¾ swimming in the same general circular
pattern ¾ contribute to this disorder, but there's no sign of ill
health. Another theory is that orcas in oceanariums spend
more time resting at the surface, so there is less water
pressure on either side of the fin for support. Orcas in their
natural environment, on the other hand, spend a great deal of
time beneath the surface of the water searching for food.

Baleen regards,
WWhale