I would say crayfish just as it's spelled. I have no idea what it is in Acadian French I'm not French but I know a lot of Acadian people.
It would be funny if the name came from little lobster, maybe "petite homard"? Not even close to crayfish.
http://www.etymonline.com/index.php?term=crayfish http://en.wiktionary.org/wiki/crayfish#Etymology
For what it's worth, it is also spelled, not just pronounced, "crawfish" in Texas and Louisiana.
The French from France asked Terry when he left and what village he was from Terry kept trying to tell them that he never was from France he had always lived here in the Maritimes they didn't believe him they thought he left France maybe ten years ago.