Mirelurk are a specific East Coast mutation AFAIK. Originally they were Chesapeake Blue Crabs mutated by FEV and Rads (which is also why they were edible... it was a bit of a salute to a greater DC regional favorite food), and in FO4 became generically just crabs mutated by FEV and Rads.
I recall but sadly Lirelurks did show up in Lake Mead.