Dex says here “In olden days, like the early 1800s, fried salt pork was a staple food aboard ships.” Perhaps aboard some ships, but the Royal Navy officially used salt beef for some meals (though it was often referred to as “salt horse”, which wasn’t too unlikely), and it was always boiled rather than fried. The RN’s ‘slush’ was the leftover fat skimmed off by the cook, and he was usually allowed to sell it to the seamen for a spread on their biscuit. It was also used for candles, and as an ointment for burns and small wounds.
Diet specifications are here and on a couple of pages linked from here.