throughout history many cultures have preserved fish and eels by salting and smoking - was such done or is it possible for crab or cray meat?

Having lived in New Orleans I've picked my share of blue crabs. The problem with accumulating then smoking crabmeat is that its so darn good, and picking is so much effort that you get hungry from all the work, and eat all the meat.

Seriously, both crayfish and crab have an exoskeleton that would be hard for smoke to permeate, so its doubtful that either was preserved by smoking. Salting requires a lot of rinsing before you can eat it, to clear the salt and re-hydrate the flesh. I am betting, however, that some enterprising Cajun found a way to preserve both in sauce piquant. That would both preserve and flavor the seafood.

You can salt or smoke anything.

all meat can be preserved like that.