"Cape Cod Turkey" is, as any Cape Codder knows, dried salt Cod. Brined, then dried in the sun until hard as stone.
The pics above are of drying cod "flakes" near Commercial Wharf, Provincetown. More pics and details here.
The starving Pilgrims would have dined well on Cod, had they known how to catch them. They were weak on survival skills (half died the first winter), but they, as you recall, had never meant to end up in the Massachusetts woods. They were headed for the Hudson River, somewhere near the Dutch city of New Amsterdam. Some reports say they were headed to what was termed "Virginia," the vast area claimed by English investors running south down the coast from New Amsterdam).
European fishermen were harvesting and drying Cod on the coast of eastern Canada 100 years before the Pilgrims arrived, and the Portuguese and Spanish (and eventually, the Italians too) figured out how to cook this wood-like substance, which they call baccala or bacala or bacalao, in interesting ways.
Here's Thoreau's amusing take on the Cape Cod cod industry. (Link fixed - well, maybe not. No time to mess with it right now)