Livingston was the name of Picard's red, Australian lion fish. It dwelled inside the tank of the ready room, aboard USS Enterprise-D from 2364 to 2371, until it was nearly destroyed at Veridian III. (TNG movie: Star Trek Generations)
Trivia
Named for TNG director and producer David Livingston, the aquarium was intact at the end of the film. It was unknown if the fish itself survived afterwards, though. The aquarium was vaguely seen again in Star Trek: First Contact, Star Trek: Insurrection, and Star Trek Nemesis.