With What Crime Was He Charged?

This one is not original. I think it was in Reader's Digest many years ago. I remember the punch line, but I will be supplying some of the extras through the story. It is not really a twist on a saying like most have been. It is more like a five-word pun. I don't think that it is one that can be solved, but maybe someone will surprise me. I hope so.

A wealthy man lived in a beautiful estate near the beach. He was rather eccentric, and he had four Atlantic porpoises in his large aquarium. A large lion was always tied at the front doors to his mansion. He had heard an old man say that a certain species of sea gull could be fed to porpoises, allowing them to live forever. Well, he loved his porpoises and set out to the beach to find sea gulls. He found the correct type and took them back home. When he arrived, he saw that his lion was sound asleep in front of the door. Not wanting to disturb him, he carefully climbed over the top of the sleeping beast and entered his home. There, he fed the gulls to his porpoises. Later that evening, he was arrested for the crime that he had committed. Do you know what crime it was?

I will supply some clues later if no one comes up with the answer. Remember, there are five puns used. I don't think that I would be able to solve it if I were trying from your end. I will wait for a few of you to reply, and then try to give a few hints.