Tuna were a type of fish which were commonly caught for food. According to the Twelfth Doctor, they were often caught with nets. (COMIC: The Body Electric)
The Sixth Doctor had many cans of tuna onboard his TARDIS. He intended them as food for Frobisher. However, Frobisher preferred to catch live fish. (AUDIO: The Holy Terror)
Alice Obiefune once made herself a tuna sandwich while travelling in the TARDIS. (COMIC: Midnight Feast)