I'll Take "What Pirates Ate" for $200...

The answer is: "Tortoises." More:

Tortoise, and to a lesser extent turtle, were ideal foods for seafarers. Giant tortoises are found only in the Galapagos and, at that time, a few remote islands in the Indian Ocean. Galapagos tortoises possess the remarkable adaptive ability to survive for months without food or water, their bodies going into a state of almost suspended animation during the periodic droughts that afflict the islands. Sailors would corral tortoises on deck for a few days while they cleared their bowels, and then stack them on their backs below deck like so many barrels of food, slaughtering them as needed for months thereafter.

Nasty!