National Marine Fisheries Service maintains quotas restricting the collection of cetaceans under the auspices of the marine mammal protection act of 1972. From 1972 through 1990 less than 1,000 animals were collected from the wild. Over that same time period about 10,000,000 cetaceans have died as a result of fishery interactions. It is true that the collected animal is removed from its social group, but there is no evidence that social groups break up afterwards. Bottlenose dolphins are generally about two years of age when collected, an age group that is subject to considerable mortality prior to maturity.
Most scientists believe small cetaceans are somewhere between dogs and chimpanzees in intelligence.
See Dolphin Training at the MN Zoo . Dolphins are more susceptible to ulcers than are most animals, but we simply don't know enough to say that the ulcers are stress induced in these species. Dolphins use sonar principally to find food, other dolphins, and have exacting control over the use of this sensory system. Dolphins are social animals that display aggression toward one another wherever they live, just like all social animals. One would think so, but the drive to stay in the group prevent them from leaving.