I don't know how they pursued a Beluga as a pet, but, they did. The flip side of this is that any contact with a wild Marine Mammal such as this is considered a "take." Scientists are just allowed so many "takes" in their studies. Perhaps this is a study of some kind or another. But, it better not be used to train a mammal for sale, either.
Both species seem to be having a good time. I suppose it gets boring at times for a Beluga whale just swimming around looking for food and friendship in the ocean. I am sure there is more to the story than meets the eye.