Trained Porpoise Released in the Open Sea.

A Pacific bottlenose porpoise, Tursiops gilli, was trained for a period of 10 weeks to swim at high speed on command and return to an underwater speaker when a specific sound cue was played. This animal was released in the open sea off Oahu, Hawaii, and worked each day for 7 days. At night it was held in an anchored floating pen. The trainer's control over the animal was probably associated with the controlled feeding of the porpoise, the development of social ties between the porpoise and trainer, and the animal's fear of unknown situations.